From b2c0a85013d492f2a80c0f938459619406643462 Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <piotr.github@karwasz.org>
Date: Thu, 14 Mar 2024 15:58:42 +0100
Subject: [PATCH 01/12] Simplify `ServiceLoaderUtil`

We make `ServiceLoaderUtil` more GraalVM-friendly by replacing the usage
of `MethodHandles.Lookup` with the requirement for the caller to
instantiate the `ServiceLoader` himself.
---
 .../log4j/util/ServiceLoaderUtilTest.java     |  25 ++-
 log4j-api/pom.xml                             |   4 +
 .../log4j/message/ThreadDumpMessage.java      |   8 +-
 .../log4j/util/OsgiServiceLocator.java        |  55 +++--
 .../logging/log4j/util/PropertiesUtil.java    |   6 +-
 .../logging/log4j/util/ProviderUtil.java      |   7 +-
 .../logging/log4j/util/ServiceLoaderUtil.java | 193 ++++++------------
 .../logging/log4j/util/StackLocator.java      |   5 +-
 .../log4j/core/appender/SmtpAppender.java     |  10 +-
 .../core/impl/ThreadContextDataInjector.java  |   7 +-
 .../logging/log4j/core/util/WatchManager.java |   5 +-
 11 files changed, 158 insertions(+), 167 deletions(-)

diff --git a/log4j-api-test/src/test/java/org/apache/logging/log4j/util/ServiceLoaderUtilTest.java b/log4j-api-test/src/test/java/org/apache/logging/log4j/util/ServiceLoaderUtilTest.java
index 09b489565c9..8ca74a0bee6 100644
--- a/log4j-api-test/src/test/java/org/apache/logging/log4j/util/ServiceLoaderUtilTest.java
+++ b/log4j-api-test/src/test/java/org/apache/logging/log4j/util/ServiceLoaderUtilTest.java
@@ -20,13 +20,15 @@
 import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
-import java.lang.invoke.MethodHandles;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.ServiceConfigurationError;
+import java.util.ServiceLoader;
 import java.util.stream.Collectors;
 import org.apache.logging.log4j.Level;
+import org.apache.logging.log4j.Logger;
 import org.apache.logging.log4j.status.StatusData;
+import org.apache.logging.log4j.status.StatusLogger;
 import org.apache.logging.log4j.test.BetterService;
 import org.apache.logging.log4j.test.ListStatusListener;
 import org.apache.logging.log4j.test.Service;
@@ -35,14 +37,26 @@
 
 public class ServiceLoaderUtilTest {
 
+    private static final Logger LOGGER = StatusLogger.getLogger();
+
     @Test
     public void testServiceResolution() {
         final List<Object> services = new ArrayList<>();
-        assertDoesNotThrow(() -> ServiceLoaderUtil.loadServices(BetterService.class, MethodHandles.lookup(), false)
+        ServiceLoaderUtil.safeStream(
+                BetterService.class,
+                ServiceLoader.load(BetterService.class, getClass().getClassLoader()),
+                LOGGER);
+        assertDoesNotThrow(() -> ServiceLoaderUtil.safeStream(
+                        BetterService.class,
+                        ServiceLoader.load(BetterService.class, getClass().getClassLoader()),
+                        LOGGER)
                 .forEach(services::add));
         assertThat(services).hasSize(1);
         services.clear();
-        assertDoesNotThrow(() -> ServiceLoaderUtil.loadServices(PropertySource.class, MethodHandles.lookup(), false)
+        assertDoesNotThrow(() -> ServiceLoaderUtil.safeStream(
+                        PropertySource.class,
+                        ServiceLoader.load(PropertySource.class, getClass().getClassLoader()),
+                        LOGGER)
                 .forEach(services::add));
         assertThat(services).hasSize(3);
     }
@@ -51,7 +65,10 @@ public void testServiceResolution() {
     @UsingStatusListener
     public void testBrokenServiceFile(final ListStatusListener listener) {
         final List<Service> services = new ArrayList<>();
-        assertDoesNotThrow(() -> ServiceLoaderUtil.loadServices(Service.class, MethodHandles.lookup(), false)
+        assertDoesNotThrow(() -> ServiceLoaderUtil.safeStream(
+                        Service.class,
+                        ServiceLoader.load(Service.class, getClass().getClassLoader()),
+                        LOGGER)
                 .forEach(services::add));
         assertEquals(2, services.size());
         // A warning for each broken service
diff --git a/log4j-api/pom.xml b/log4j-api/pom.xml
index 082fd2f6574..853ebe4d4aa 100644
--- a/log4j-api/pom.xml
+++ b/log4j-api/pom.xml
@@ -36,6 +36,10 @@
     <bnd-multi-release>true</bnd-multi-release>
     <!-- Differs from OSGi bundle name -->
     <bnd-module-name>org.apache.logging.log4j</bnd-module-name>
+    <bnd-extra-package-options>
+      <!-- Not exported by most OSGi system bundles, hence we use the system classloader to load `sun.reflect.Reflection` -->
+      !sun.reflect
+    </bnd-extra-package-options>
     <bnd-extra-module-options>
       <!-- Used in StringBuilders through reflection -->
       java.sql;static=true,
diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/message/ThreadDumpMessage.java b/log4j-api/src/main/java/org/apache/logging/log4j/message/ThreadDumpMessage.java
index 18ed7befe4f..4ddbdc5c5f4 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/message/ThreadDumpMessage.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/message/ThreadDumpMessage.java
@@ -24,10 +24,11 @@
 import java.io.InvalidObjectException;
 import java.io.ObjectInputStream;
 import java.io.Serializable;
-import java.lang.invoke.MethodHandles;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.ServiceLoader;
 import org.apache.logging.log4j.message.ThreadDumpMessage.ThreadInfoFactory;
+import org.apache.logging.log4j.status.StatusLogger;
 import org.apache.logging.log4j.util.Lazy;
 import org.apache.logging.log4j.util.ServiceLoaderUtil;
 import org.apache.logging.log4j.util.StringBuilderFormattable;
@@ -61,7 +62,10 @@ private ThreadDumpMessage(final String formattedMsg, final String title) {
     }
 
     private static ThreadInfoFactory initFactory() {
-        return ServiceLoaderUtil.loadServices(ThreadInfoFactory.class, MethodHandles.lookup(), false)
+        return ServiceLoaderUtil.safeStream(
+                        ThreadInfoFactory.class,
+                        ServiceLoader.load(ThreadInfoFactory.class, ThreadDumpMessage.class.getClassLoader()),
+                        StatusLogger.getLogger())
                 .findFirst()
                 .orElseGet(BasicThreadInfoFactory::new);
     }
diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/util/OsgiServiceLocator.java b/log4j-api/src/main/java/org/apache/logging/log4j/util/OsgiServiceLocator.java
index d061ccbd6db..46157290c18 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/util/OsgiServiceLocator.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/util/OsgiServiceLocator.java
@@ -24,6 +24,7 @@
 import org.osgi.framework.Bundle;
 import org.osgi.framework.BundleContext;
 import org.osgi.framework.FrameworkUtil;
+import org.osgi.framework.wiring.BundleRevision;
 
 public class OsgiServiceLocator {
 
@@ -57,29 +58,53 @@ public static <T> Stream<T> loadServices(final Class<T> serviceType, final Looku
 
     public static <T> Stream<T> loadServices(final Class<T> serviceType, final Lookup lookup, final boolean verbose) {
         final Class<?> lookupClass = Objects.requireNonNull(lookup, "lookup").lookupClass();
-        final Bundle bundle = FrameworkUtil.getBundle(Objects.requireNonNull(lookupClass, "lookupClass"));
-        if (bundle != null) {
+        return loadServices(serviceType, lookupClass, StatusLogger.getLogger());
+    }
+
+    static <T> Stream<T> loadServices(final Class<T> serviceType, final Class<?> callerClass, final Logger logger) {
+        final Bundle bundle = FrameworkUtil.getBundle(callerClass);
+        if (bundle != null && !isFragment(bundle)) {
             final BundleContext ctx = bundle.getBundleContext();
             if (ctx == null) {
-                if (verbose) {
-                    StatusLogger.getLogger()
-                            .error(
-                                    "Unable to load OSGI services: The bundle has no valid BundleContext for serviceType = {}, lookup = {}, lookupClass = {}, bundle = {}",
-                                    serviceType,
-                                    lookup,
-                                    lookupClass,
-                                    bundle);
-                }
+                logger.warn(
+                        "Unable to load OSGi services for service {}: bundle {} (state {}) does not have a valid BundleContext",
+                        serviceType::getName,
+                        bundle::getSymbolicName,
+                        () -> {
+                            switch (bundle.getState()) {
+                                case Bundle.UNINSTALLED:
+                                    return "UNINSTALLED";
+                                case Bundle.INSTALLED:
+                                    return "INSTALLED";
+                                case Bundle.RESOLVED:
+                                    return "RESOLVED";
+                                case Bundle.STARTING:
+                                    return "STARTING";
+                                case Bundle.STOPPING:
+                                    return "STOPPING";
+                                case Bundle.ACTIVE:
+                                    return "ACTIVE";
+                                default:
+                                    return "UNKNOWN";
+                            }
+                        });
+
             } else {
                 try {
                     return ctx.getServiceReferences(serviceType, null).stream().map(ctx::getService);
-                } catch (Throwable e) {
-                    if (verbose) {
-                        StatusLogger.getLogger().error("Unable to load OSGI services for service {}", serviceType, e);
-                    }
+                } catch (final Exception e) {
+                    logger.error("Unable to load OSGI services for service {}", serviceType, e);
                 }
             }
         }
         return Stream.empty();
     }
+
+    private static boolean isFragment(final Bundle bundle) {
+        try {
+            return (bundle.adapt(BundleRevision.class).getTypes() & BundleRevision.TYPE_FRAGMENT) != 0;
+        } catch (final SecurityException ignored) {
+            return false;
+        }
+    }
 }
diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/util/PropertiesUtil.java b/log4j-api/src/main/java/org/apache/logging/log4j/util/PropertiesUtil.java
index daf9163203a..310f432edd4 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/util/PropertiesUtil.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/util/PropertiesUtil.java
@@ -21,7 +21,6 @@
 import aQute.bnd.annotation.spi.ServiceConsumer;
 import java.io.IOException;
 import java.io.InputStream;
-import java.lang.invoke.MethodHandles;
 import java.nio.charset.Charset;
 import java.time.Duration;
 import java.time.temporal.ChronoUnit;
@@ -486,7 +485,10 @@ private Environment(final PropertySource propertySource) {
             }
             sources.add(propertySource);
             // We don't log anything on the status logger.
-            ServiceLoaderUtil.loadServices(PropertySource.class, MethodHandles.lookup(), false, false)
+            ServiceLoaderUtil.safeStream(
+                            PropertySource.class,
+                            ServiceLoader.load(PropertySource.class, PropertiesUtil.class.getClassLoader()),
+                            LOGGER)
                     .forEach(sources::add);
 
             reload();
diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/util/ProviderUtil.java b/log4j-api/src/main/java/org/apache/logging/log4j/util/ProviderUtil.java
index a669bf71433..c02526b4a0e 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/util/ProviderUtil.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/util/ProviderUtil.java
@@ -24,13 +24,13 @@
 import aQute.bnd.annotation.spi.ServiceConsumer;
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import java.io.IOException;
-import java.lang.invoke.MethodHandles;
 import java.net.URL;
 import java.util.Collection;
 import java.util.Comparator;
 import java.util.Enumeration;
 import java.util.HashSet;
 import java.util.Properties;
+import java.util.ServiceLoader;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 import java.util.stream.Collectors;
@@ -152,7 +152,10 @@ static void lazyInit() {
                 STARTUP_LOCK.lockInterruptibly();
                 try {
                     if (PROVIDER == null) {
-                        ServiceLoaderUtil.loadServices(Provider.class, MethodHandles.lookup(), false)
+                        ServiceLoaderUtil.safeStream(
+                                        Provider.class,
+                                        ServiceLoader.load(Provider.class, ProviderUtil.class.getClassLoader()),
+                                        LOGGER)
                                 .filter(provider -> validVersion(provider.getVersions()))
                                 .forEach(ProviderUtil::addProvider);
 
diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/util/ServiceLoaderUtil.java b/log4j-api/src/main/java/org/apache/logging/log4j/util/ServiceLoaderUtil.java
index cf906eab69b..30b56f83b56 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/util/ServiceLoaderUtil.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/util/ServiceLoaderUtil.java
@@ -16,30 +16,41 @@
  */
 package org.apache.logging.log4j.util;
 
-import java.lang.invoke.CallSite;
-import java.lang.invoke.LambdaMetafactory;
-import java.lang.invoke.MethodHandle;
-import java.lang.invoke.MethodHandles.Lookup;
-import java.lang.invoke.MethodType;
-import java.security.AccessController;
-import java.security.PrivilegedAction;
-import java.util.Collections;
+import static java.util.Objects.requireNonNull;
+
+import aQute.bnd.annotation.baseline.BaselineIgnore;
+import java.util.Collection;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.ServiceConfigurationError;
 import java.util.ServiceLoader;
-import java.util.Set;
-import java.util.Spliterator;
+import java.util.Spliterators;
 import java.util.function.Consumer;
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
 import org.apache.logging.log4j.Logger;
-import org.apache.logging.log4j.status.StatusLogger;
 
 /**
- * This class should be considered internal.
+ * An utility class to retrieve services in a safe way.
+ * <p>
+ *     This class should be considered internal.
+ * </p>
+ * <p>
+ *     A common source of {@link ServiceLoader} failures, when running in a multi-classloader environment, is the
+ *     presence of multiple classes with the same class name in the same classloader hierarchy. Since {@code
+ *     ServiceLoader} retrieves services by class name, it is entirely possible that the registered services don't
+ *     extend the required interface and cause an exception to be thrown by {@code ServiceLoader}.
+ * </p>
+ * <p>
+ *     The purpose of this class is to:
+ * </p>
+ * <ol>
+ *     <li>skip faulty services, allowing for a partial retrieval of the good ones,</li>
+ *     <li>allow to integrate other sources of services like OSGi services.</li>
+ * </ol>
  */
 @InternalApi
+@BaselineIgnore("2.24.0")
 public final class ServiceLoaderUtil {
 
     private static final int MAX_BROKEN_SERVICES = 8;
@@ -47,110 +58,43 @@ public final class ServiceLoaderUtil {
     private ServiceLoaderUtil() {}
 
     /**
-     * Retrieves the available services from the caller's classloader.
-     *
-     * Broken services will be ignored.
-     *
-     * @param <T>         The service type.
-     * @param serviceType The class of the service.
-     * @param lookup      The calling class data.
-     * @return A stream of service instances.
-     */
-    public static <T> Stream<T> loadServices(final Class<T> serviceType, final Lookup lookup) {
-        return loadServices(serviceType, lookup, false);
-    }
-
-    /**
-     * Retrieves the available services from the caller's classloader and possibly
-     * the thread context classloader.
-     *
-     * Broken services will be ignored.
-     *
-     * @param <T>         The service type.
-     * @param serviceType The class of the service.
-     * @param lookup      The calling class data.
-     * @param useTccl     If true the thread context classloader will also be used.
-     * @return A stream of service instances.
+     * Retrieves services registered with {@link ServiceLoader}
+     * <p>
+     *     It ignores the most common service loading errors.
+     * </p>
+     * @param serviceType The service type to use for OSGi service retrieval.
+     * @param serviceLoader The service loader instance to use.
+     * @param logger The logger to use to report service failures.
+     * @return A stream of all correctly loaded services.
+     * @since 2.24.0
      */
-    public static <T> Stream<T> loadServices(final Class<T> serviceType, final Lookup lookup, final boolean useTccl) {
-        return loadServices(serviceType, lookup, useTccl, true);
-    }
-
-    static <T> Stream<T> loadServices(
-            final Class<T> serviceType, final Lookup lookup, final boolean useTccl, final boolean verbose) {
-        final ClassLoader classLoader = lookup.lookupClass().getClassLoader();
-        Stream<T> services = loadClassloaderServices(serviceType, lookup, classLoader, verbose);
-        if (useTccl) {
-            final ClassLoader contextClassLoader = LoaderUtil.getThreadContextClassLoader();
-            if (contextClassLoader != classLoader) {
-                services = Stream.concat(
-                        services, loadClassloaderServices(serviceType, lookup, contextClassLoader, verbose));
-            }
-        }
-        if (OsgiServiceLocator.isAvailable()) {
-            services = Stream.concat(services, OsgiServiceLocator.loadServices(serviceType, lookup, verbose));
-        }
-        final Set<Class<?>> classes = new HashSet<>();
-        // only the first occurrence of a class
-        return services.filter(service -> classes.add(service.getClass()));
-    }
-
-    static <T> Stream<T> loadClassloaderServices(
-            final Class<T> serviceType, final Lookup lookup, final ClassLoader classLoader, final boolean verbose) {
-        return StreamSupport.stream(new ServiceLoaderSpliterator<T>(serviceType, lookup, classLoader, verbose), false);
+    public static <S> Stream<S> safeStream(
+            final Class<S> serviceType, final ServiceLoader<? extends S> serviceLoader, final Logger logger) {
+        requireNonNull(serviceLoader, "serviceLoader");
+        final Collection<Class<?>> classes = new HashSet<>();
+        final Stream<S> services =
+                StreamSupport.stream(new ServiceLoaderSpliterator<>(serviceType, serviceLoader, logger), false);
+        // Caller class may be null
+        final Class<?> callerClass = StackLocatorUtil.getCallerClass(2);
+        final Stream<S> allServices = OsgiServiceLocator.isAvailable() && callerClass != null
+                ? Stream.concat(services, OsgiServiceLocator.loadServices(serviceType, callerClass, logger))
+                : services;
+        return allServices
+                // only the first occurrence of a class
+                .filter(service -> classes.add(service.getClass()));
     }
 
-    static <T> Iterable<T> callServiceLoader(
-            final Lookup lookup, final Class<T> serviceType, final ClassLoader classLoader, final boolean verbose) {
-        try {
-            // Creates a lambda in the caller's domain that calls `ServiceLoader`
-            final MethodHandle loadHandle = lookup.findStatic(
-                    ServiceLoader.class,
-                    "load",
-                    MethodType.methodType(ServiceLoader.class, Class.class, ClassLoader.class));
-            final CallSite callSite = LambdaMetafactory.metafactory(
-                    lookup,
-                    "run",
-                    MethodType.methodType(PrivilegedAction.class, Class.class, ClassLoader.class),
-                    MethodType.methodType(Object.class),
-                    loadHandle,
-                    MethodType.methodType(ServiceLoader.class));
-            final PrivilegedAction<ServiceLoader<T>> action = (PrivilegedAction<ServiceLoader<T>>)
-                    callSite.getTarget() //
-                            .bindTo(serviceType)
-                            .bindTo(classLoader)
-                            .invoke();
-            final ServiceLoader<T> serviceLoader;
-            if (System.getSecurityManager() == null) {
-                serviceLoader = action.run();
-            } else {
-                final MethodHandle privilegedHandle = lookup.findStatic(
-                        AccessController.class,
-                        "doPrivileged",
-                        MethodType.methodType(Object.class, PrivilegedAction.class));
-                serviceLoader = (ServiceLoader<T>) privilegedHandle.invoke(action);
-            }
-            return serviceLoader;
-        } catch (Throwable e) {
-            if (verbose) {
-                StatusLogger.getLogger().error("Unable to load services for service {}", serviceType, e);
-            }
-        }
-        return Collections.emptyList();
-    }
-
-    private static class ServiceLoaderSpliterator<S> implements Spliterator<S> {
-
-        private final Iterator<S> serviceIterator;
-        private final Logger logger;
+    private static final class ServiceLoaderSpliterator<S> extends Spliterators.AbstractSpliterator<S> {
         private final String serviceName;
+        private final Iterator<? extends S> serviceIterator;
+        private final Logger logger;
 
-        public ServiceLoaderSpliterator(
-                final Class<S> serviceType, final Lookup lookup, final ClassLoader classLoader, final boolean verbose) {
-            this.serviceIterator =
-                    callServiceLoader(lookup, serviceType, classLoader, verbose).iterator();
-            this.logger = verbose ? StatusLogger.getLogger() : null;
-            this.serviceName = serviceType.toString();
+        private ServiceLoaderSpliterator(
+                final Class<S> serviceType, final Iterable<? extends S> serviceLoader, final Logger logger) {
+            super(Long.MAX_VALUE, ORDERED | NONNULL | IMMUTABLE);
+            this.serviceName = serviceType.getName();
+            this.serviceIterator = serviceLoader.iterator();
+            this.logger = logger;
         }
 
         @Override
@@ -162,33 +106,14 @@ public boolean tryAdvance(final Consumer<? super S> action) {
                         action.accept(serviceIterator.next());
                         return true;
                     }
-                } catch (ServiceConfigurationError | LinkageError e) {
-                    if (logger != null) {
-                        logger.warn("Unable to load service class for service {}", serviceName, e);
-                    }
-                } catch (Throwable e) {
-                    if (logger != null) {
-                        logger.warn("Unable to load service class for service {}", serviceName, e);
-                    }
+                } catch (final ServiceConfigurationError | LinkageError e) {
+                    logger.warn("Unable to load implementation for service {}", serviceName, e);
+                } catch (final Exception e) {
+                    logger.warn("Unexpected exception  while loading implementation for service {}", serviceName, e);
                     throw e;
                 }
             }
             return false;
         }
-
-        @Override
-        public Spliterator<S> trySplit() {
-            return null;
-        }
-
-        @Override
-        public long estimateSize() {
-            return Long.MAX_VALUE;
-        }
-
-        @Override
-        public int characteristics() {
-            return NONNULL | IMMUTABLE;
-        }
     }
 }
diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/util/StackLocator.java b/log4j-api/src/main/java/org/apache/logging/log4j/util/StackLocator.java
index bc20af0daf3..e5b50fc7ca2 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/util/StackLocator.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/util/StackLocator.java
@@ -69,7 +69,10 @@ public final class StackLocator {
         Method getCallerClassMethod;
         int java7u25CompensationOffset = 0;
         try {
-            final Class<?> sunReflectionClass = LoaderUtil.loadClass("sun.reflect.Reflection");
+            // Do not use `LoaderUtil` here, since it causes a cycle of dependencies:
+            // LoaderUtil -> PropertiesUtil -> ServiceLoaderUtil -> StackLocator
+            final Class<?> sunReflectionClass =
+                    Class.forName("sun.reflect.Reflection", true, ClassLoader.getSystemClassLoader());
             getCallerClassMethod = sunReflectionClass.getDeclaredMethod("getCallerClass", int.class);
             Object o = getCallerClassMethod.invoke(null, 0);
             getCallerClassMethod.invoke(null, 0);
diff --git a/log4j-core/src/main/java/org/apache/logging/log4j/core/appender/SmtpAppender.java b/log4j-core/src/main/java/org/apache/logging/log4j/core/appender/SmtpAppender.java
index c1299311eaa..b610603b4be 100644
--- a/log4j-core/src/main/java/org/apache/logging/log4j/core/appender/SmtpAppender.java
+++ b/log4j-core/src/main/java/org/apache/logging/log4j/core/appender/SmtpAppender.java
@@ -17,7 +17,7 @@
 package org.apache.logging.log4j.core.appender;
 
 import java.io.Serializable;
-import java.lang.invoke.MethodHandles;
+import java.util.ServiceLoader;
 import org.apache.logging.log4j.core.Appender;
 import org.apache.logging.log4j.core.Core;
 import org.apache.logging.log4j.core.Filter;
@@ -45,6 +45,7 @@
 import org.apache.logging.log4j.core.net.ssl.SslConfiguration;
 import org.apache.logging.log4j.core.util.Booleans;
 import org.apache.logging.log4j.core.util.Integers;
+import org.apache.logging.log4j.status.StatusLogger;
 import org.apache.logging.log4j.util.ServiceLoaderUtil;
 import org.apache.logging.log4j.util.Strings;
 
@@ -300,8 +301,11 @@ public SmtpAppender build() {
                     bufferSize,
                     sslConfiguration,
                     getFilter().toString());
-            final MailManagerFactory factory = ServiceLoaderUtil.loadServices(
-                            MailManagerFactory.class, MethodHandles.lookup())
+            final MailManagerFactory factory = ServiceLoaderUtil.safeStream(
+                            MailManagerFactory.class,
+                            ServiceLoader.load(
+                                    MailManagerFactory.class, getClass().getClassLoader()),
+                            StatusLogger.getLogger())
                     .findAny()
                     .orElseGet(() -> SmtpManager.FACTORY);
             final MailManager smtpManager = AbstractManager.getManager(data.getManagerName(), factory, data);
diff --git a/log4j-core/src/main/java/org/apache/logging/log4j/core/impl/ThreadContextDataInjector.java b/log4j-core/src/main/java/org/apache/logging/log4j/core/impl/ThreadContextDataInjector.java
index 24f34936e6d..332b877a51f 100644
--- a/log4j-core/src/main/java/org/apache/logging/log4j/core/impl/ThreadContextDataInjector.java
+++ b/log4j-core/src/main/java/org/apache/logging/log4j/core/impl/ThreadContextDataInjector.java
@@ -19,13 +19,13 @@
 import aQute.bnd.annotation.Cardinality;
 import aQute.bnd.annotation.Resolution;
 import aQute.bnd.annotation.spi.ServiceConsumer;
-import java.lang.invoke.MethodHandles;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.ServiceLoader;
 import java.util.concurrent.ConcurrentLinkedDeque;
 import org.apache.logging.log4j.Logger;
 import org.apache.logging.log4j.ThreadContext;
@@ -79,7 +79,10 @@ public static void initServiceProviders() {}
 
     private static List<ContextDataProvider> getServiceProviders() {
         final List<ContextDataProvider> providers = new ArrayList<>();
-        ServiceLoaderUtil.loadServices(ContextDataProvider.class, MethodHandles.lookup(), false)
+        ServiceLoaderUtil.safeStream(
+                        ContextDataProvider.class,
+                        ServiceLoader.load(ContextDataProvider.class, ThreadContextDataInjector.class.getClassLoader()),
+                        LOGGER)
                 .forEach(providers::add);
         return Collections.unmodifiableList(providers);
     }
diff --git a/log4j-core/src/main/java/org/apache/logging/log4j/core/util/WatchManager.java b/log4j-core/src/main/java/org/apache/logging/log4j/core/util/WatchManager.java
index 491c212f6f0..1761498087b 100644
--- a/log4j-core/src/main/java/org/apache/logging/log4j/core/util/WatchManager.java
+++ b/log4j-core/src/main/java/org/apache/logging/log4j/core/util/WatchManager.java
@@ -20,12 +20,12 @@
 import aQute.bnd.annotation.Resolution;
 import aQute.bnd.annotation.spi.ServiceConsumer;
 import java.io.File;
-import java.lang.invoke.MethodHandles;
 import java.util.Date;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.ServiceLoader;
 import java.util.UUID;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
@@ -143,7 +143,8 @@ public void run() {
 
     public WatchManager(final ConfigurationScheduler scheduler) {
         this.scheduler = Objects.requireNonNull(scheduler, "scheduler");
-        eventServiceList = ServiceLoaderUtil.loadServices(WatchEventService.class, MethodHandles.lookup(), true)
+        eventServiceList = ServiceLoaderUtil.safeStream(
+                        WatchEventService.class, ServiceLoader.load(WatchEventService.class), logger)
                 .collect(Collectors.toList());
     }
 

From 9b455b2d5c4e6ea5e906f6d2f98679e7b52c5fe8 Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <piotr.github@karwasz.org>
Date: Thu, 14 Mar 2024 16:14:04 +0100
Subject: [PATCH 02/12] Adapt `ReusableMessage` to be used in 3.x

---
 .../log4j/message/ReusableMessage.java        |  8 +++++++
 .../message/ReusableParameterizedMessage.java | 23 ++++++++++---------
 .../logging/log4j/message/package-info.java   |  2 +-
 3 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/message/ReusableMessage.java b/log4j-api/src/main/java/org/apache/logging/log4j/message/ReusableMessage.java
index 35e8fa3919c..5a5d264e680 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/message/ReusableMessage.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/message/ReusableMessage.java
@@ -18,6 +18,7 @@
 
 import org.apache.logging.log4j.util.PerformanceSensitive;
 import org.apache.logging.log4j.util.StringBuilderFormattable;
+import org.osgi.annotation.versioning.ProviderType;
 
 /**
  * Messages implementing this interface are reused between logging calls.
@@ -29,6 +30,7 @@
  * @since 2.6
  */
 @PerformanceSensitive("allocation")
+@ProviderType
 public interface ReusableMessage extends Message, StringBuilderFormattable {
 
     /**
@@ -69,4 +71,10 @@ public interface ReusableMessage extends Message, StringBuilderFormattable {
      * @return an immutable snapshot of this message
      */
     Message memento();
+
+    /**
+     * Resets the object to a clean state.
+     * @since 2.24.0
+     */
+    void clear();
 }
diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/message/ReusableParameterizedMessage.java b/log4j-api/src/main/java/org/apache/logging/log4j/message/ReusableParameterizedMessage.java
index d55b98ae700..053a5bf8f1c 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/message/ReusableParameterizedMessage.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/message/ReusableParameterizedMessage.java
@@ -135,26 +135,27 @@ private static Throwable determineThrowable(final Object[] args, final int argCo
         return null;
     }
 
-    ReusableParameterizedMessage set(final String messagePattern, final Object... arguments) {
+    public ReusableParameterizedMessage set(final String messagePattern, final Object... arguments) {
         init(messagePattern, arguments == null ? 0 : arguments.length, arguments);
         varargs = arguments;
         return this;
     }
 
-    ReusableParameterizedMessage set(final String messagePattern, final Object p0) {
+    public ReusableParameterizedMessage set(final String messagePattern, final Object p0) {
         params[0] = p0;
         init(messagePattern, 1, params);
         return this;
     }
 
-    ReusableParameterizedMessage set(final String messagePattern, final Object p0, final Object p1) {
+    public ReusableParameterizedMessage set(final String messagePattern, final Object p0, final Object p1) {
         params[0] = p0;
         params[1] = p1;
         init(messagePattern, 2, params);
         return this;
     }
 
-    ReusableParameterizedMessage set(final String messagePattern, final Object p0, final Object p1, final Object p2) {
+    public ReusableParameterizedMessage set(
+            final String messagePattern, final Object p0, final Object p1, final Object p2) {
         params[0] = p0;
         params[1] = p1;
         params[2] = p2;
@@ -162,7 +163,7 @@ ReusableParameterizedMessage set(final String messagePattern, final Object p0, f
         return this;
     }
 
-    ReusableParameterizedMessage set(
+    public ReusableParameterizedMessage set(
             final String messagePattern, final Object p0, final Object p1, final Object p2, final Object p3) {
         params[0] = p0;
         params[1] = p1;
@@ -172,7 +173,7 @@ ReusableParameterizedMessage set(
         return this;
     }
 
-    ReusableParameterizedMessage set(
+    public ReusableParameterizedMessage set(
             final String messagePattern,
             final Object p0,
             final Object p1,
@@ -188,7 +189,7 @@ ReusableParameterizedMessage set(
         return this;
     }
 
-    ReusableParameterizedMessage set(
+    public ReusableParameterizedMessage set(
             final String messagePattern,
             final Object p0,
             final Object p1,
@@ -206,7 +207,7 @@ ReusableParameterizedMessage set(
         return this;
     }
 
-    ReusableParameterizedMessage set(
+    public ReusableParameterizedMessage set(
             final String messagePattern,
             final Object p0,
             final Object p1,
@@ -226,7 +227,7 @@ ReusableParameterizedMessage set(
         return this;
     }
 
-    ReusableParameterizedMessage set(
+    public ReusableParameterizedMessage set(
             final String messagePattern,
             final Object p0,
             final Object p1,
@@ -248,7 +249,7 @@ ReusableParameterizedMessage set(
         return this;
     }
 
-    ReusableParameterizedMessage set(
+    public ReusableParameterizedMessage set(
             final String messagePattern,
             final Object p0,
             final Object p1,
@@ -272,7 +273,7 @@ ReusableParameterizedMessage set(
         return this;
     }
 
-    ReusableParameterizedMessage set(
+    public ReusableParameterizedMessage set(
             final String messagePattern,
             final Object p0,
             final Object p1,
diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/message/package-info.java b/log4j-api/src/main/java/org/apache/logging/log4j/message/package-info.java
index 49286fab779..24632f8d7b5 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/message/package-info.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/message/package-info.java
@@ -22,7 +22,7 @@
 /**
  * Bumped to 2.22.0, since FormattedMessage behavior changed.
  */
-@Version("2.22.0")
+@Version("2.24.0")
 package org.apache.logging.log4j.message;
 
 import org.osgi.annotation.bundle.Export;

From ffe06dd6507a64149e0e0bc3bbffaef575802fed Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <piotr.github@karwasz.org>
Date: Fri, 15 Mar 2024 10:05:24 +0100
Subject: [PATCH 03/12] Remove deprecations from functional interfaces

---
 .../map/UnmodifiableArrayBackedMapTest.java   |  30 ++---
 .../org/apache/logging/log4j/LogBuilder.java  | 110 +++++++++++-------
 .../org/apache/logging/log4j/LogManager.java  |  35 +++---
 .../java/org/apache/logging/log4j/Logger.java |  66 +++--------
 .../apache/logging/log4j/util/BiConsumer.java |   4 +-
 .../apache/logging/log4j/util/LambdaUtil.java |   3 -
 .../logging/log4j/util/MessageSupplier.java   |   4 +-
 .../apache/logging/log4j/util/Supplier.java   |   5 +-
 8 files changed, 119 insertions(+), 138 deletions(-)

diff --git a/log4j-api-test/src/test/java/org/apache/logging/log4j/internal/map/UnmodifiableArrayBackedMapTest.java b/log4j-api-test/src/test/java/org/apache/logging/log4j/internal/map/UnmodifiableArrayBackedMapTest.java
index efcee80a159..9652034d70f 100644
--- a/log4j-api-test/src/test/java/org/apache/logging/log4j/internal/map/UnmodifiableArrayBackedMapTest.java
+++ b/log4j-api-test/src/test/java/org/apache/logging/log4j/internal/map/UnmodifiableArrayBackedMapTest.java
@@ -24,6 +24,7 @@
 import static org.junit.jupiter.api.Assertions.fail;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -31,6 +32,7 @@
 import java.util.LinkedHashSet;
 import java.util.Map;
 import java.util.Set;
+import org.apache.logging.log4j.util.ReadOnlyStringMap;
 import org.apache.logging.log4j.util.TriConsumer;
 import org.junit.jupiter.api.Test;
 
@@ -238,32 +240,18 @@ public void testEqualsWhenOneValueDiffers() {
 
     @Test
     public void testForEachBiConsumer_JavaUtil() {
-        UnmodifiableArrayBackedMap map = UnmodifiableArrayBackedMap.EMPTY_MAP.copyAndPutAll(getTestParameters());
-        Set<String> keys = new HashSet<>();
-        java.util.function.BiConsumer<String, String> java_util_action =
-                new java.util.function.BiConsumer<String, String>() {
-                    @Override
-                    public void accept(String key, String value) {
-                        keys.add(key);
-                    }
-                };
-        map.forEach(java_util_action);
+        final Map<String, String> map = UnmodifiableArrayBackedMap.EMPTY_MAP.copyAndPutAll(getTestParameters());
+        final Collection<String> keys = new HashSet<>();
+        map.forEach((key, value) -> keys.add(key));
         assertEquals(map.keySet(), keys);
     }
 
     @Test
     public void testForEachBiConsumer_Log4jUtil() {
-        UnmodifiableArrayBackedMap map = UnmodifiableArrayBackedMap.EMPTY_MAP.copyAndPutAll(getTestParameters());
-        Set<String> keys = new HashSet<>();
-        org.apache.logging.log4j.util.BiConsumer<String, String> log4j_util_action =
-                new org.apache.logging.log4j.util.BiConsumer<String, String>() {
-                    @Override
-                    public void accept(String key, String value) {
-                        keys.add(key);
-                    }
-                };
-        map.forEach(log4j_util_action);
-        assertEquals(map.keySet(), keys);
+        final ReadOnlyStringMap map = UnmodifiableArrayBackedMap.EMPTY_MAP.copyAndPutAll(getTestParameters());
+        final Collection<String> keys = new HashSet<>();
+        map.forEach((key, value) -> keys.add(key));
+        assertEquals(map.toMap().keySet(), keys);
     }
 
     @Test
diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/LogBuilder.java b/log4j-api/src/main/java/org/apache/logging/log4j/LogBuilder.java
index 91d3083e4a3..992d2875138 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/LogBuilder.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/LogBuilder.java
@@ -32,7 +32,7 @@ public interface LogBuilder {
      * @param marker The Marker to log.
      * @return The LogBuilder.
      */
-    default LogBuilder withMarker(Marker marker) {
+    default LogBuilder withMarker(final Marker marker) {
         return this;
     }
 
@@ -41,7 +41,7 @@ default LogBuilder withMarker(Marker marker) {
      * @param throwable The Throwable to log.
      * @return the LogBuilder.
      */
-    default LogBuilder withThrowable(Throwable throwable) {
+    default LogBuilder withThrowable(final Throwable throwable) {
         return this;
     }
 
@@ -59,7 +59,7 @@ default LogBuilder withLocation() {
      * @param location The stack trace element to include in the log event.
      * @return The LogBuilder.
      */
-    default LogBuilder withLocation(StackTraceElement location) {
+    default LogBuilder withLocation(final StackTraceElement location) {
         return this;
     }
 
@@ -67,13 +67,13 @@ default LogBuilder withLocation(StackTraceElement location) {
      * Causes all the data collected to be logged along with the message. Interface default method does nothing.
      * @param message The message to log.
      */
-    default void log(CharSequence message) {}
+    default void log(final CharSequence message) {}
 
     /**
      * Causes all the data collected to be logged along with the message. Interface default method does nothing.
      * @param message The message to log.
      */
-    default void log(String message) {}
+    default void log(final String message) {}
 
     /**
      * Logs a message with parameters. Interface default method does nothing.
@@ -83,7 +83,7 @@ default void log(String message) {}
      *
      * @see org.apache.logging.log4j.util.Unbox
      */
-    default void log(String message, Object... params) {}
+    default void log(final String message, final Object... params) {}
 
     /**
      * Causes all the data collected to be logged along with the message and parameters.
@@ -91,21 +91,19 @@ default void log(String message, Object... params) {}
      * @param message The message.
      * @param params Parameters to the message.
      */
-    @SuppressWarnings("deprecation")
-    default void log(String message, Supplier<?>... params) {}
+    default void log(final String message, final Supplier<?>... params) {}
 
     /**
      * Causes all the data collected to be logged along with the message. Interface default method does nothing.
      * @param message The message to log.
      */
-    default void log(Message message) {}
+    default void log(final Message message) {}
 
     /**
      * Causes all the data collected to be logged along with the message. Interface default method does nothing.
      * @param messageSupplier The supplier of the message to log.
      */
-    @SuppressWarnings("deprecation")
-    default void log(Supplier<Message> messageSupplier) {}
+    default void log(final Supplier<Message> messageSupplier) {}
 
     /**
      * Causes all the data collected to be logged along with the message.
@@ -114,7 +112,6 @@ default void log(Supplier<Message> messageSupplier) {}
      * @return the message logger or {@code null} if no logging occurred.
      * @since 2.20
      */
-    @SuppressWarnings("deprecation")
     default Message logAndGet(final Supplier<Message> messageSupplier) {
         return null;
     }
@@ -123,7 +120,7 @@ default Message logAndGet(final Supplier<Message> messageSupplier) {
      * Causes all the data collected to be logged along with the message. Interface default method does nothing.
      * @param message The message to log.
      */
-    default void log(Object message) {}
+    default void log(final Object message) {}
 
     /**
      * Logs a message with parameters. Interface default method does nothing.
@@ -133,7 +130,7 @@ default void log(Object message) {}
      *
      * @see org.apache.logging.log4j.util.Unbox
      */
-    default void log(String message, Object p0) {}
+    default void log(final String message, final Object p0) {}
 
     /**
      * Logs a message with parameters. Interface default method does nothing.
@@ -144,7 +141,7 @@ default void log(String message, Object p0) {}
      *
      * @see org.apache.logging.log4j.util.Unbox
      */
-    default void log(String message, Object p0, Object p1) {}
+    default void log(final String message, final Object p0, final Object p1) {}
 
     /**
      * Logs a message with parameters. Interface default method does nothing.
@@ -156,7 +153,7 @@ default void log(String message, Object p0, Object p1) {}
      *
      * @see org.apache.logging.log4j.util.Unbox
      */
-    default void log(String message, Object p0, Object p1, Object p2) {}
+    default void log(final String message, final Object p0, final Object p1, final Object p2) {}
 
     /**
      * Logs a message with parameters. Interface default method does nothing.
@@ -169,7 +166,7 @@ default void log(String message, Object p0, Object p1, Object p2) {}
      *
      * @see org.apache.logging.log4j.util.Unbox
      */
-    default void log(String message, Object p0, Object p1, Object p2, Object p3) {}
+    default void log(final String message, final Object p0, final Object p1, final Object p2, final Object p3) {}
 
     /**
      * Logs a message with parameters. Interface default method does nothing.
@@ -183,7 +180,13 @@ default void log(String message, Object p0, Object p1, Object p2, Object p3) {}
      *
      * @see org.apache.logging.log4j.util.Unbox
      */
-    default void log(String message, Object p0, Object p1, Object p2, Object p3, Object p4) {}
+    default void log(
+            final String message,
+            final Object p0,
+            final Object p1,
+            final Object p2,
+            final Object p3,
+            final Object p4) {}
 
     /**
      * Logs a message with parameters. Interface default method does nothing.
@@ -198,7 +201,14 @@ default void log(String message, Object p0, Object p1, Object p2, Object p3, Obj
      *
      * @see org.apache.logging.log4j.util.Unbox
      */
-    default void log(String message, Object p0, Object p1, Object p2, Object p3, Object p4, Object p5) {}
+    default void log(
+            final String message,
+            final Object p0,
+            final Object p1,
+            final Object p2,
+            final Object p3,
+            final Object p4,
+            final Object p5) {}
 
     /**
      * Logs a message with parameters.
@@ -214,7 +224,15 @@ default void log(String message, Object p0, Object p1, Object p2, Object p3, Obj
      *
      * @see org.apache.logging.log4j.util.Unbox
      */
-    default void log(String message, Object p0, Object p1, Object p2, Object p3, Object p4, Object p5, Object p6) {}
+    default void log(
+            final String message,
+            final Object p0,
+            final Object p1,
+            final Object p2,
+            final Object p3,
+            final Object p4,
+            final Object p5,
+            final Object p6) {}
 
     /**
      * Logs a message with parameters. Interface default method does nothing.
@@ -232,7 +250,15 @@ default void log(String message, Object p0, Object p1, Object p2, Object p3, Obj
      * @see org.apache.logging.log4j.util.Unbox
      */
     default void log(
-            String message, Object p0, Object p1, Object p2, Object p3, Object p4, Object p5, Object p6, Object p7) {}
+            final String message,
+            final Object p0,
+            final Object p1,
+            final Object p2,
+            final Object p3,
+            final Object p4,
+            final Object p5,
+            final Object p6,
+            final Object p7) {}
 
     /**
      * Logs a message with parameters. Interface default method does nothing.
@@ -251,16 +277,16 @@ default void log(
      * @see org.apache.logging.log4j.util.Unbox
      */
     default void log(
-            String message,
-            Object p0,
-            Object p1,
-            Object p2,
-            Object p3,
-            Object p4,
-            Object p5,
-            Object p6,
-            Object p7,
-            Object p8) {}
+            final String message,
+            final Object p0,
+            final Object p1,
+            final Object p2,
+            final Object p3,
+            final Object p4,
+            final Object p5,
+            final Object p6,
+            final Object p7,
+            final Object p8) {}
 
     /**
      * Logs a message with parameters. Interface default method does nothing.
@@ -280,17 +306,17 @@ default void log(
      * @see org.apache.logging.log4j.util.Unbox
      */
     default void log(
-            String message,
-            Object p0,
-            Object p1,
-            Object p2,
-            Object p3,
-            Object p4,
-            Object p5,
-            Object p6,
-            Object p7,
-            Object p8,
-            Object p9) {}
+            final String message,
+            final Object p0,
+            final Object p1,
+            final Object p2,
+            final Object p3,
+            final Object p4,
+            final Object p5,
+            final Object p6,
+            final Object p7,
+            final Object p8,
+            final Object p9) {}
 
     /**
      * Causes all the data collected to be logged. Default implementatoin does nothing.
diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/LogManager.java b/log4j-api/src/main/java/org/apache/logging/log4j/LogManager.java
index d7def7ac7ee..cdb91c57658 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/LogManager.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/LogManager.java
@@ -41,7 +41,7 @@
 public class LogManager {
 
     /**
-     * Log4j property to set to the fully qualified class name of a custom implementation of
+     * Log4j's property to set to the fully qualified class name of a custom implementation of
      * {@link LoggerContextFactory}.
      * @deprecated Replaced since 2.24.0 with {@value org.apache.logging.log4j.spi.Provider#PROVIDER_PROPERTY_NAME}.
      */
@@ -49,7 +49,7 @@ public class LogManager {
     public static final String FACTORY_PROPERTY_NAME = "log4j2.loggerContextFactory";
 
     /**
-     * The name of the root Logger is {@value #ROOT_LOGGER_NAME}.
+     * The name of the root Logger.
      */
     public static final String ROOT_LOGGER_NAME = Strings.EMPTY;
 
@@ -315,10 +315,10 @@ protected static LoggerContext getContext(
     /**
      * Shutdown using the LoggerContext appropriate for the caller of this method.
      * This is equivalent to calling {@code LogManager.shutdown(false)}.
-     *
-     * This call is synchronous and will block until shut down is complete.
-     * This may include flushing pending log events over network connections.
-     *
+     * <p>
+     *     This call is synchronous and will block until shut down is complete. This may include flushing pending log
+     *     events over network connections.
+     * </p>
      * @since 2.6
      */
     public static void shutdown() {
@@ -328,9 +328,10 @@ public static void shutdown() {
     /**
      * Shutdown the logging system if the logging system supports it.
      * This is equivalent to calling {@code LogManager.shutdown(LogManager.getContext(currentContext))}.
-     *
-     * This call is synchronous and will block until shut down is complete.
-     * This may include flushing pending log events over network connections.
+     * <p>
+     *     This call is synchronous and will block until shut down is complete. This may include flushing pending log
+     *     events over network connections.
+     * </p>
      *
      * @param currentContext if true a default LoggerContext (may not be the LoggerContext used to create a Logger
      *            for the calling class) will be used.
@@ -347,9 +348,10 @@ public static void shutdown(final boolean currentContext) {
     /**
      * Shutdown the logging system if the logging system supports it.
      * This is equivalent to calling {@code LogManager.shutdown(LogManager.getContext(currentContext))}.
-     *
-     * This call is synchronous and will block until shut down is complete.
-     * This may include flushing pending log events over network connections.
+     * <p>
+     *     This call is synchronous and will block until shut down is complete. This may include flushing pending log
+     *     events over network connections.
+     * </p>
      *
      * @param currentContext if true a default LoggerContext (may not be the LoggerContext used to create a Logger
      *            for the calling class) will be used.
@@ -366,9 +368,10 @@ public static void shutdown(final boolean currentContext, final boolean allConte
 
     /**
      * Shutdown the logging system if the logging system supports it.
-     *
-     * This call is synchronous and will block until shut down is complete.
-     * This may include flushing pending log events over network connections.
+     * <p>
+     *     This call is synchronous and will block until shut down is complete. This may include flushing pending log
+     *     events over network connections.
+     * </p>
      *
      * @param context the LoggerContext.
      * @since 2.6
@@ -461,7 +464,7 @@ public static Logger getFormatterLogger(final Class<?> clazz) {
      * Short-hand for {@code getLogger(value, StringFormatterMessageFactory.INSTANCE)}
      * </p>
      *
-     * @param value The value's whose class name should be used as the Logger name.
+     * @param value The value whose class name should be used as the Logger name.
      * @return The Logger, created with a {@link StringFormatterMessageFactory}
      * @throws UnsupportedOperationException if {@code value} is {@code null} and the calling class cannot be
      *             determined.
diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/Logger.java b/log4j-api/src/main/java/org/apache/logging/log4j/Logger.java
index 7dc872e21a1..ef461ddfe31 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/Logger.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/Logger.java
@@ -200,7 +200,6 @@ public interface Logger {
      * @param paramSuppliers An array of functions, which when called, produce the desired log message parameters.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void debug(Marker marker, String message, Supplier<?>... paramSuppliers);
 
     /**
@@ -222,7 +221,6 @@ public interface Logger {
      *            message factory.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void debug(Marker marker, Supplier<?> messageSupplier);
 
     /**
@@ -235,7 +233,6 @@ public interface Logger {
      * @param throwable A Throwable or null.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void debug(Marker marker, Supplier<?> messageSupplier, Throwable throwable);
 
     /**
@@ -329,7 +326,6 @@ public interface Logger {
      * @param paramSuppliers An array of functions, which when called, produce the desired log message parameters.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void debug(String message, Supplier<?>... paramSuppliers);
 
     /**
@@ -348,7 +344,6 @@ public interface Logger {
      *            message factory.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void debug(Supplier<?> messageSupplier);
 
     /**
@@ -360,7 +355,6 @@ public interface Logger {
      * @param throwable the {@code Throwable} to log, including its stack trace.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void debug(Supplier<?> messageSupplier, Throwable throwable);
 
     /**
@@ -811,7 +805,6 @@ void debug(
      * @param paramSuppliers An array of functions, which when called, produce the desired log message parameters.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void error(Marker marker, String message, Supplier<?>... paramSuppliers);
 
     /**
@@ -833,7 +826,6 @@ void debug(
      *            message factory.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void error(Marker marker, Supplier<?> messageSupplier);
 
     /**
@@ -846,7 +838,6 @@ void debug(
      * @param throwable A Throwable or null.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void error(Marker marker, Supplier<?> messageSupplier, Throwable throwable);
 
     /**
@@ -940,7 +931,6 @@ void debug(
      * @param paramSuppliers An array of functions, which when called, produce the desired log message parameters.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void error(String message, Supplier<?>... paramSuppliers);
 
     /**
@@ -959,7 +949,6 @@ void debug(
      *            message factory.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void error(Supplier<?> messageSupplier);
 
     /**
@@ -971,7 +960,6 @@ void debug(
      * @param throwable the {@code Throwable} to log, including its stack trace.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void error(Supplier<?> messageSupplier, Throwable throwable);
 
     /**
@@ -1414,7 +1402,6 @@ void error(
      * @param paramSuppliers An array of functions, which when called, produce the desired log message parameters.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void fatal(Marker marker, String message, Supplier<?>... paramSuppliers);
 
     /**
@@ -1436,7 +1423,6 @@ void error(
      *            message factory.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void fatal(Marker marker, Supplier<?> messageSupplier);
 
     /**
@@ -1449,7 +1435,6 @@ void error(
      * @param throwable A Throwable or null.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void fatal(Marker marker, Supplier<?> messageSupplier, Throwable throwable);
 
     /**
@@ -1543,7 +1528,6 @@ void error(
      * @param paramSuppliers An array of functions, which when called, produce the desired log message parameters.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void fatal(String message, Supplier<?>... paramSuppliers);
 
     /**
@@ -1562,7 +1546,6 @@ void error(
      *            message factory.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void fatal(Supplier<?> messageSupplier);
 
     /**
@@ -1574,7 +1557,6 @@ void error(
      * @param throwable the {@code Throwable} to log, including its stack trace.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void fatal(Supplier<?> messageSupplier, Throwable throwable);
 
     /**
@@ -1901,12 +1883,13 @@ void fatal(
 
     /**
      * Gets the message factory used to convert message Objects and Strings/CharSequences into actual log Messages.
-     *
-     * Since version 2.6, Log4j internally uses message factories that implement the {@link MessageFactory2} interface.
-     * From version 2.6.2, the return type of this method was changed from {@link MessageFactory} to
-     * {@code <MF extends MessageFactory> MF}. The returned factory will always implement {@link MessageFactory2},
-     * but the return type of this method could not be changed to {@link MessageFactory2} without breaking binary
-     * compatibility.
+     * <p>
+     *     Since version 2.6, Log4j internally uses message factories that implement the {@link MessageFactory2}
+     *     interface. From version 2.6.2, the return type of this method was changed from {@link MessageFactory} to
+     *     {@code <MF extends MessageFactory> MF}. The returned factory will always implement {@link MessageFactory2},
+     *     but the return type of this method could not be changed to {@link MessageFactory2} without breaking binary
+     *     compatibility.
+     * </p>
      *
      * @return the message factory, as an instance of {@link MessageFactory2}
      */
@@ -2030,7 +2013,6 @@ void fatal(
      * @param paramSuppliers An array of functions, which when called, produce the desired log message parameters.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void info(Marker marker, String message, Supplier<?>... paramSuppliers);
 
     /**
@@ -2052,7 +2034,6 @@ void fatal(
      *            message factory.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void info(Marker marker, Supplier<?> messageSupplier);
 
     /**
@@ -2065,7 +2046,6 @@ void fatal(
      * @param throwable A Throwable or null.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void info(Marker marker, Supplier<?> messageSupplier, Throwable throwable);
 
     /**
@@ -2159,7 +2139,6 @@ void fatal(
      * @param paramSuppliers An array of functions, which when called, produce the desired log message parameters.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void info(String message, Supplier<?>... paramSuppliers);
 
     /**
@@ -2178,7 +2157,6 @@ void fatal(
      *            message factory.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void info(Supplier<?> messageSupplier);
 
     /**
@@ -2190,7 +2168,6 @@ void fatal(
      * @param throwable the {@code Throwable} to log, including its stack trace.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void info(Supplier<?> messageSupplier, Throwable throwable);
 
     /**
@@ -2737,7 +2714,6 @@ void info(
      * @param paramSuppliers An array of functions, which when called, produce the desired log message parameters.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void log(Level level, Marker marker, String message, Supplier<?>... paramSuppliers);
 
     /**
@@ -2760,7 +2736,6 @@ void info(
      *            message factory.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void log(Level level, Marker marker, Supplier<?> messageSupplier);
 
     /**
@@ -2774,7 +2749,6 @@ void info(
      * @param throwable A Throwable or null.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void log(Level level, Marker marker, Supplier<?> messageSupplier, Throwable throwable);
 
     /**
@@ -2878,7 +2852,6 @@ void info(
      * @param paramSuppliers An array of functions, which when called, produce the desired log message parameters.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void log(Level level, String message, Supplier<?>... paramSuppliers);
 
     /**
@@ -2899,7 +2872,6 @@ void info(
      *            message factory.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void log(Level level, Supplier<?> messageSupplier);
 
     /**
@@ -2912,7 +2884,6 @@ void info(
      * @param throwable the {@code Throwable} to log, including its stack log.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void log(Level level, Supplier<?> messageSupplier, Throwable throwable);
 
     /**
@@ -3435,7 +3406,6 @@ void log(
      * @param paramSuppliers An array of functions, which when called, produce the desired log message parameters.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void trace(Marker marker, String message, Supplier<?>... paramSuppliers);
 
     /**
@@ -3458,7 +3428,6 @@ void log(
      *            message factory.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void trace(Marker marker, Supplier<?> messageSupplier);
 
     /**
@@ -3471,7 +3440,6 @@ void log(
      * @param throwable A Throwable or null.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void trace(Marker marker, Supplier<?> messageSupplier, Throwable throwable);
 
     /**
@@ -3567,7 +3535,6 @@ void log(
      * @param paramSuppliers An array of functions, which when called, produce the desired log message parameters.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void trace(String message, Supplier<?>... paramSuppliers);
 
     /**
@@ -3587,7 +3554,6 @@ void log(
      *            message factory.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void trace(Supplier<?> messageSupplier);
 
     /**
@@ -3599,7 +3565,6 @@ void log(
      * @param throwable the {@code Throwable} to log, including its stack trace.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void trace(Supplier<?> messageSupplier, Throwable throwable);
 
     /**
@@ -3967,7 +3932,6 @@ void trace(
      *
      * @since 2.6
      */
-    @SuppressWarnings("deprecation")
     EntryMessage traceEntry(Supplier<?>... paramSuppliers);
 
     /**
@@ -3986,7 +3950,6 @@ void trace(
      *
      * @since 2.6
      */
-    @SuppressWarnings("deprecation")
     EntryMessage traceEntry(String format, Supplier<?>... paramSuppliers);
 
     /**
@@ -4205,7 +4168,6 @@ void trace(
      * @param paramSuppliers An array of functions, which when called, produce the desired log message parameters.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void warn(Marker marker, String message, Supplier<?>... paramSuppliers);
 
     /**
@@ -4227,7 +4189,6 @@ void trace(
      *            message factory.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void warn(Marker marker, Supplier<?> messageSupplier);
 
     /**
@@ -4240,7 +4201,6 @@ void trace(
      * @param throwable A Throwable or null.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void warn(Marker marker, Supplier<?> messageSupplier, Throwable throwable);
 
     /**
@@ -4334,7 +4294,6 @@ void trace(
      * @param paramSuppliers An array of functions, which when called, produce the desired log message parameters.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void warn(String message, Supplier<?>... paramSuppliers);
 
     /**
@@ -4353,7 +4312,6 @@ void trace(
      *            message factory.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void warn(Supplier<?> messageSupplier);
 
     /**
@@ -4365,7 +4323,6 @@ void trace(
      * @param throwable the {@code Throwable} to log, including its stack warn.
      * @since 2.4
      */
-    @SuppressWarnings("deprecation")
     void warn(Supplier<?> messageSupplier, Throwable throwable);
 
     /**
@@ -4695,7 +4652,12 @@ void warn(
      * @since 2.13.0
      */
     default void logMessage(
-            Level level, Marker marker, String fqcn, StackTraceElement location, Message message, Throwable throwable) {
+            final Level level,
+            final Marker marker,
+            final String fqcn,
+            final StackTraceElement location,
+            final Message message,
+            final Throwable throwable) {
         // noop
     }
 
@@ -4768,7 +4730,7 @@ default LogBuilder always() {
      * @return a LogBuilder.
      * @since 2.13.0
      */
-    default LogBuilder atLevel(Level level) {
+    default LogBuilder atLevel(final Level level) {
         return LogBuilder.NOOP;
     }
 }
diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/util/BiConsumer.java b/log4j-api/src/main/java/org/apache/logging/log4j/util/BiConsumer.java
index 7be09f0431b..e7cedb6bb3b 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/util/BiConsumer.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/util/BiConsumer.java
@@ -24,12 +24,14 @@
  * @see ReadOnlyStringMap
  * @since 2.7
  */
-public interface BiConsumer<K, V> {
+@FunctionalInterface
+public interface BiConsumer<K, V> extends java.util.function.BiConsumer<K, V> {
 
     /**
      * Performs the operation given the specified arguments.
      * @param k the first input argument
      * @param v the second input argument
      */
+    @Override
     void accept(K k, V v);
 }
diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/util/LambdaUtil.java b/log4j-api/src/main/java/org/apache/logging/log4j/util/LambdaUtil.java
index bab3171e7f3..ef1f3b0b321 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/util/LambdaUtil.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/util/LambdaUtil.java
@@ -35,7 +35,6 @@ private LambdaUtil() {}
      * @return an array containing the results of evaluating the lambda expressions (or {@code null} if the suppliers
      *         array was {@code null}
      */
-    @SuppressWarnings("deprecation")
     public static Object[] getAll(final Supplier<?>... suppliers) {
         if (suppliers == null) {
             return null;
@@ -54,7 +53,6 @@ public static Object[] getAll(final Supplier<?>... suppliers) {
      * @return the results of evaluating the lambda expression (or {@code null} if the supplier
      *         was {@code null}
      */
-    @SuppressWarnings("deprecation")
     public static Object get(final Supplier<?> supplier) {
         if (supplier == null) {
             return null;
@@ -83,7 +81,6 @@ public static Message get(final MessageSupplier supplier) {
      * @return the Message resulting from evaluating the lambda expression or the Message created by the factory for
      * supplied values that are not of type Message
      */
-    @SuppressWarnings("deprecation")
     public static Message getMessage(final Supplier<?> supplier, final MessageFactory messageFactory) {
         if (supplier == null) {
             return null;
diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/util/MessageSupplier.java b/log4j-api/src/main/java/org/apache/logging/log4j/util/MessageSupplier.java
index 8b135713505..d3776a1a744 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/util/MessageSupplier.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/util/MessageSupplier.java
@@ -33,12 +33,14 @@
  *
  * @since 2.4
  */
-public interface MessageSupplier {
+@FunctionalInterface
+public interface MessageSupplier extends Supplier<Message> {
 
     /**
      * Gets a Message.
      *
      * @return a Message
      */
+    @Override
     Message get();
 }
diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/util/Supplier.java b/log4j-api/src/main/java/org/apache/logging/log4j/util/Supplier.java
index aaa4d9b89a1..45ad5c667d2 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/util/Supplier.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/util/Supplier.java
@@ -31,14 +31,15 @@
  *
  * @since 2.4
  */
+@FunctionalInterface
 @InternalApi
-@Deprecated
-public interface Supplier<T> {
+public interface Supplier<T> extends java.util.function.Supplier<T> {
 
     /**
      * Gets a value.
      *
      * @return a value
      */
+    @Override
     T get();
 }

From f3c0f6ff63abae21153e2b6818ad1dab2ed83faa Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <piotr.github@karwasz.org>
Date: Fri, 15 Mar 2024 14:28:49 +0100
Subject: [PATCH 04/12] Add `Strings#trimToOptional`

---
 .../org/apache/logging/log4j/util/Strings.java     | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/util/Strings.java b/log4j-api/src/main/java/org/apache/logging/log4j/util/Strings.java
index bee54324f44..8eea0e782c8 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/util/Strings.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/util/Strings.java
@@ -21,6 +21,7 @@
 import java.util.Iterator;
 import java.util.Locale;
 import java.util.Objects;
+import java.util.Optional;
 
 /**
  * <em>Consider this class private.</em>
@@ -288,6 +289,19 @@ public static String trimToNull(final String str) {
         return isEmpty(ts) ? null : ts;
     }
 
+    /**
+     * Removes control characters from both ends of this String returning {@code Optional.empty()} if the String is
+     * empty ("") after the trim or if it is {@code null}.
+     * @param str The String to trim.
+     * @return An Optional containing the String.
+     *
+     * @see #trimToNull(String)
+     * @since 2.24.0
+     */
+    public static Optional<String> trimToOptional(final String str) {
+        return Optional.ofNullable(str).map(String::trim).filter(s -> !s.isEmpty());
+    }
+
     private Strings() {
         // empty
     }

From f7184e5018f9e5c07b0a82dfcdaf9c87550e0abb Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <piotr.github@karwasz.org>
Date: Fri, 15 Mar 2024 14:29:50 +0100
Subject: [PATCH 05/12] Make default message factories GraalVM friendly

---
 .../message/DefaultFlowMessageFactory.java    | 22 ++++++++++++-------
 .../logging/log4j/spi/AbstractLogger.java     | 14 ++----------
 2 files changed, 16 insertions(+), 20 deletions(-)

diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/message/DefaultFlowMessageFactory.java b/log4j-api/src/main/java/org/apache/logging/log4j/message/DefaultFlowMessageFactory.java
index 1c6fcd3f459..3ca2aeba41a 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/message/DefaultFlowMessageFactory.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/message/DefaultFlowMessageFactory.java
@@ -17,8 +17,7 @@
 package org.apache.logging.log4j.message;
 
 import java.io.Serializable;
-import org.apache.logging.log4j.spi.AbstractLogger;
-import org.apache.logging.log4j.util.LoaderUtil;
+import java.util.Objects;
 import org.apache.logging.log4j.util.StringBuilderFormattable;
 import org.apache.logging.log4j.util.StringBuilders;
 import org.apache.logging.log4j.util.Strings;
@@ -34,6 +33,8 @@ public class DefaultFlowMessageFactory implements FlowMessageFactory, Serializab
     private static final String ENTRY_DEFAULT_PREFIX = "Enter";
     private static final long serialVersionUID = 8578655591131397576L;
 
+    public static final FlowMessageFactory INSTANCE = new DefaultFlowMessageFactory();
+
     private final String entryText;
     private final String exitText;
     private final MessageFactory messageFactory;
@@ -51,17 +52,22 @@ public DefaultFlowMessageFactory() {
      * @param exitText the text to use for trace exit, like {@code "Exit"}.
      */
     public DefaultFlowMessageFactory(final String entryText, final String exitText) {
+        this(entryText, exitText, createDefaultMessageFactory());
+    }
+
+    public DefaultFlowMessageFactory(final MessageFactory messageFactory) {
+        this(ENTRY_DEFAULT_PREFIX, EXIT_DEFAULT_PREFIX, Objects.requireNonNull(messageFactory));
+    }
+
+    private DefaultFlowMessageFactory(
+            final String entryText, final String exitText, final MessageFactory messageFactory) {
         this.entryText = entryText;
         this.exitText = exitText;
-        this.messageFactory = createDefaultMessageFactory();
+        this.messageFactory = messageFactory;
     }
 
     private static MessageFactory createDefaultMessageFactory() {
-        try {
-            return LoaderUtil.newInstanceOf(AbstractLogger.DEFAULT_MESSAGE_FACTORY_CLASS);
-        } catch (final ReflectiveOperationException e) {
-            throw new IllegalStateException(e);
-        }
+        return ParameterizedMessageFactory.INSTANCE;
     }
 
     private static class AbstractFlowMessage implements FlowMessage, StringBuilderFormattable {
diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/spi/AbstractLogger.java b/log4j-api/src/main/java/org/apache/logging/log4j/spi/AbstractLogger.java
index d9543f17b52..30d0cffef02 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/spi/AbstractLogger.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/spi/AbstractLogger.java
@@ -35,7 +35,6 @@
 import org.apache.logging.log4j.status.StatusLogger;
 import org.apache.logging.log4j.util.Constants;
 import org.apache.logging.log4j.util.LambdaUtil;
-import org.apache.logging.log4j.util.LoaderUtil;
 import org.apache.logging.log4j.util.MessageSupplier;
 import org.apache.logging.log4j.util.PerformanceSensitive;
 import org.apache.logging.log4j.util.StackLocatorUtil;
@@ -198,12 +197,7 @@ protected Message catchingMsg(final Throwable throwable) {
     }
 
     private static MessageFactory2 createDefaultMessageFactory() {
-        try {
-            final MessageFactory result = LoaderUtil.newInstanceOf(DEFAULT_MESSAGE_FACTORY_CLASS);
-            return narrow(result);
-        } catch (final ReflectiveOperationException e) {
-            throw new IllegalStateException(e);
-        }
+        return ParameterizedMessageFactory.INSTANCE;
     }
 
     private static MessageFactory2 narrow(final MessageFactory result) {
@@ -214,11 +208,7 @@ private static MessageFactory2 narrow(final MessageFactory result) {
     }
 
     private static FlowMessageFactory createDefaultFlowMessageFactory() {
-        try {
-            return LoaderUtil.newInstanceOf(DEFAULT_FLOW_MESSAGE_FACTORY_CLASS);
-        } catch (final ReflectiveOperationException e) {
-            throw new IllegalStateException(e);
-        }
+        return DefaultFlowMessageFactory.INSTANCE;
     }
 
     @Override

From 91579573a58ab16b0070c83e2a89c8170335d87e Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <piotr.github@karwasz.org>
Date: Fri, 15 Mar 2024 16:04:10 +0100
Subject: [PATCH 06/12] Port `Tags` from 3.x

---
 .../apache/logging/log4j/test/junit/Tags.java | 33 +++++++++++++++++++
 .../log4j/test/junit/package-info.java        |  2 +-
 2 files changed, 34 insertions(+), 1 deletion(-)
 create mode 100644 log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/Tags.java

diff --git a/log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/Tags.java b/log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/Tags.java
new file mode 100644
index 00000000000..06bef43b06d
--- /dev/null
+++ b/log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/Tags.java
@@ -0,0 +1,33 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to you under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.logging.log4j.test.junit;
+
+/**
+ * A set of tags for JUnit 5 tests.
+ */
+public final class Tags {
+
+    /**
+     * Marks tests that don't modify the global environment.
+     * <p>
+     *     These tests can safely be run in parallel.
+     * </p>
+     */
+    public static final String PARALLEL = "parallel";
+
+    private Tags() {}
+}
diff --git a/log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/package-info.java b/log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/package-info.java
index 22e32873bee..3207042de87 100644
--- a/log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/package-info.java
+++ b/log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/package-info.java
@@ -15,7 +15,7 @@
  * limitations under the license.
  */
 @Export
-@Version("2.23.1")
+@Version("2.24.0")
 package org.apache.logging.log4j.test.junit;
 
 import org.osgi.annotation.bundle.Export;

From c2c3a018255b7d2cd2289965340a383f2adf8480 Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <piotr.github@karwasz.org>
Date: Tue, 19 Mar 2024 14:11:41 +0100
Subject: [PATCH 07/12] Remove reflection from `log4j-to-jul` and
 `log4j-to-slf4j`

By removing the reflective instantiation of `LoggerContextFactory` and
`ThreadContextMap`, we make `log4j-to-jul` and `log4j-to-slf4j` more
GraalVM-friendly.
---
 .../logging/log4j/tojul/JULProvider.java       | 16 +++++++++++++++-
 .../logging/log4j/tojul/package-info.java      |  2 +-
 .../apache/logging/slf4j/SLF4JProvider.java    | 18 +++++++++++++++++-
 .../org/apache/logging/slf4j/package-info.java |  2 +-
 4 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/log4j-to-jul/src/main/java/org/apache/logging/log4j/tojul/JULProvider.java b/log4j-to-jul/src/main/java/org/apache/logging/log4j/tojul/JULProvider.java
index 9022d9abeb8..0f371f43ef0 100644
--- a/log4j-to-jul/src/main/java/org/apache/logging/log4j/tojul/JULProvider.java
+++ b/log4j-to-jul/src/main/java/org/apache/logging/log4j/tojul/JULProvider.java
@@ -18,6 +18,7 @@
 
 import aQute.bnd.annotation.Resolution;
 import aQute.bnd.annotation.spi.ServiceProvider;
+import org.apache.logging.log4j.spi.LoggerContextFactory;
 import org.apache.logging.log4j.spi.Provider;
 
 /**
@@ -27,7 +28,20 @@
  */
 @ServiceProvider(value = Provider.class, resolution = Resolution.OPTIONAL)
 public class JULProvider extends Provider {
+    private static final LoggerContextFactory CONTEXT_FACTORY = new JULLoggerContextFactory();
+
     public JULProvider() {
-        super(20, "2.6.0", JULLoggerContextFactory.class, null);
+        super(20, CURRENT_VERSION);
+    }
+
+    @Override
+    public LoggerContextFactory getLoggerContextFactory() {
+        return CONTEXT_FACTORY;
+    }
+
+    @Override
+    public String getThreadContextMap() {
+        // JUL does not provide an MDC implementation
+        return NO_OP_CONTEXT_MAP;
     }
 }
diff --git a/log4j-to-jul/src/main/java/org/apache/logging/log4j/tojul/package-info.java b/log4j-to-jul/src/main/java/org/apache/logging/log4j/tojul/package-info.java
index f333fffe246..aa117c7995c 100644
--- a/log4j-to-jul/src/main/java/org/apache/logging/log4j/tojul/package-info.java
+++ b/log4j-to-jul/src/main/java/org/apache/logging/log4j/tojul/package-info.java
@@ -21,7 +21,7 @@
  * @author <a href="http://www.vorburger.ch">Michael Vorburger.ch</a> for Google
  */
 @Export
-@Version("2.20.1")
+@Version("2.24.0")
 package org.apache.logging.log4j.tojul;
 
 import org.osgi.annotation.bundle.Export;
diff --git a/log4j-to-slf4j/src/main/java/org/apache/logging/slf4j/SLF4JProvider.java b/log4j-to-slf4j/src/main/java/org/apache/logging/slf4j/SLF4JProvider.java
index b8514c4f632..318d7937f66 100644
--- a/log4j-to-slf4j/src/main/java/org/apache/logging/slf4j/SLF4JProvider.java
+++ b/log4j-to-slf4j/src/main/java/org/apache/logging/slf4j/SLF4JProvider.java
@@ -18,14 +18,30 @@
 
 import aQute.bnd.annotation.Resolution;
 import aQute.bnd.annotation.spi.ServiceProvider;
+import org.apache.logging.log4j.spi.LoggerContextFactory;
 import org.apache.logging.log4j.spi.Provider;
+import org.apache.logging.log4j.spi.ThreadContextMap;
 
 /**
  * Bind the Log4j API to SLF4J.
  */
 @ServiceProvider(value = Provider.class, resolution = Resolution.OPTIONAL)
 public class SLF4JProvider extends Provider {
+
+    private static final LoggerContextFactory CONTEXT_FACTORY = new SLF4JLoggerContextFactory();
+    private static final ThreadContextMap THREAD_CONTEXT_MAP = new MDCContextMap();
+
     public SLF4JProvider() {
-        super(15, "2.6.0", SLF4JLoggerContextFactory.class, MDCContextMap.class);
+        super(15, CURRENT_VERSION);
+    }
+
+    @Override
+    public LoggerContextFactory getLoggerContextFactory() {
+        return CONTEXT_FACTORY;
+    }
+
+    @Override
+    public ThreadContextMap getThreadContextMapInstance() {
+        return THREAD_CONTEXT_MAP;
     }
 }
diff --git a/log4j-to-slf4j/src/main/java/org/apache/logging/slf4j/package-info.java b/log4j-to-slf4j/src/main/java/org/apache/logging/slf4j/package-info.java
index e354601ca71..ba4cb130be1 100644
--- a/log4j-to-slf4j/src/main/java/org/apache/logging/slf4j/package-info.java
+++ b/log4j-to-slf4j/src/main/java/org/apache/logging/slf4j/package-info.java
@@ -18,7 +18,7 @@
  * SLF4J support.
  */
 @Export
-@Version("2.20.1")
+@Version("2.24.0")
 package org.apache.logging.slf4j;
 
 import org.osgi.annotation.bundle.Export;

From a567c580ff51d645c710c8edd396679c58beea11 Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <piotr.github@karwasz.org>
Date: Tue, 19 Mar 2024 14:11:41 +0100
Subject: [PATCH 08/12] Add constants to mark global resource usage

---
 .../logging/log4j/test/junit/Resources.java   | 33 ++++++++++++++++---
 1 file changed, 29 insertions(+), 4 deletions(-)

diff --git a/log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/Resources.java b/log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/Resources.java
index 980900cd965..8956311e499 100644
--- a/log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/Resources.java
+++ b/log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/Resources.java
@@ -20,11 +20,36 @@
 
 /**
  * Constants to use the {@link ResourceLock} annotation.
- *
  */
-public class Resources {
+public final class Resources {
+
+    /**
+     * Marks tests that require access to {@link org.apache.logging.log4j.LogManager} methods or change its
+     * underlying {@link org.apache.logging.log4j.spi.LoggerContextFactory} implementation.
+     */
+    public static final String LOG_MANAGER = "log4j.LogManager";
+
+    /**
+     * Marks tests that require access to {@link org.apache.logging.log4j.ThreadContext} methods or change its
+     * underlying {@link org.apache.logging.log4j.spi.ThreadContextMap} implementation.
+     */
+    public static final String THREAD_CONTEXT = "log4j.ThreadContext";
+
+    /**
+     * Marks tests that require access to {@link org.apache.logging.log4j.MarkerManager} methods.
+     */
+    public static final String MARKER_MANAGER = "log4j.MarkerManager";
+
+    /**
+     * Marks tests that requires access to {@link org.apache.logging.log4j.Level} static methods to create new levels.
+     */
+    public static final String LEVEL = "log4j.Level";
 
-    public static final String THREAD_CONTEXT = "log4j2.ThreadContext";
+    /**
+     * Marks tests that require access to {@link org.apache.logging.log4j.status.StatusLogger} static methods or
+     * change its underlying implementation.
+     */
+    public static final String STATUS_LOGGER = "log4j.StatusLogger";
 
-    public static final String MARKER_MANAGER = "log4j2.MarkerManager";
+    private Resources() {}
 }

From 08a17c3e1fbf23498ce64ce9da6bdd161edc7a2b Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <piotr.github@karwasz.org>
Date: Fri, 22 Mar 2024 11:32:24 +0100
Subject: [PATCH 09/12] Apply suggestions of review #2392

---
 .../apache/logging/log4j/test/junit/Tags.java | 33 -------------------
 .../message/DefaultFlowMessageFactory.java    | 26 +++------------
 .../apache/logging/log4j/util/Strings.java    | 14 --------
 3 files changed, 5 insertions(+), 68 deletions(-)
 delete mode 100644 log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/Tags.java

diff --git a/log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/Tags.java b/log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/Tags.java
deleted file mode 100644
index 06bef43b06d..00000000000
--- a/log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/Tags.java
+++ /dev/null
@@ -1,33 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to you under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.apache.logging.log4j.test.junit;
-
-/**
- * A set of tags for JUnit 5 tests.
- */
-public final class Tags {
-
-    /**
-     * Marks tests that don't modify the global environment.
-     * <p>
-     *     These tests can safely be run in parallel.
-     * </p>
-     */
-    public static final String PARALLEL = "parallel";
-
-    private Tags() {}
-}
diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/message/DefaultFlowMessageFactory.java b/log4j-api/src/main/java/org/apache/logging/log4j/message/DefaultFlowMessageFactory.java
index 3ca2aeba41a..57dbd29b8ab 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/message/DefaultFlowMessageFactory.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/message/DefaultFlowMessageFactory.java
@@ -17,7 +17,6 @@
 package org.apache.logging.log4j.message;
 
 import java.io.Serializable;
-import java.util.Objects;
 import org.apache.logging.log4j.util.StringBuilderFormattable;
 import org.apache.logging.log4j.util.StringBuilders;
 import org.apache.logging.log4j.util.Strings;
@@ -37,7 +36,6 @@ public class DefaultFlowMessageFactory implements FlowMessageFactory, Serializab
 
     private final String entryText;
     private final String exitText;
-    private final MessageFactory messageFactory;
 
     /**
      * Constructs a message factory with {@code "Enter"} and {@code "Exit"} as the default flow strings.
@@ -52,22 +50,8 @@ public DefaultFlowMessageFactory() {
      * @param exitText the text to use for trace exit, like {@code "Exit"}.
      */
     public DefaultFlowMessageFactory(final String entryText, final String exitText) {
-        this(entryText, exitText, createDefaultMessageFactory());
-    }
-
-    public DefaultFlowMessageFactory(final MessageFactory messageFactory) {
-        this(ENTRY_DEFAULT_PREFIX, EXIT_DEFAULT_PREFIX, Objects.requireNonNull(messageFactory));
-    }
-
-    private DefaultFlowMessageFactory(
-            final String entryText, final String exitText, final MessageFactory messageFactory) {
         this.entryText = entryText;
         this.exitText = exitText;
-        this.messageFactory = messageFactory;
-    }
-
-    private static MessageFactory createDefaultMessageFactory() {
-        return ParameterizedMessageFactory.INSTANCE;
     }
 
     private static class AbstractFlowMessage implements FlowMessage, StringBuilderFormattable {
@@ -200,9 +184,9 @@ public EntryMessage newEntryMessage(final String format, final Object... params)
         final boolean hasFormat = Strings.isNotEmpty(format);
         final Message message;
         if (params == null || params.length == 0) {
-            message = hasFormat ? messageFactory.newMessage(format) : null;
+            message = hasFormat ? ParameterizedMessageFactory.INSTANCE.newMessage(format) : null;
         } else if (hasFormat) {
-            message = messageFactory.newMessage(format, params);
+            message = ParameterizedMessageFactory.INSTANCE.newMessage(format, params);
         } else {
             final StringBuilder sb = new StringBuilder("params(");
             for (int i = 0; i < params.length; i++) {
@@ -212,7 +196,7 @@ public EntryMessage newEntryMessage(final String format, final Object... params)
                 sb.append("{}");
             }
             sb.append(")");
-            message = messageFactory.newMessage(sb.toString(), params);
+            message = ParameterizedMessageFactory.INSTANCE.newMessage(sb.toString(), params);
         }
         return newEntryMessage(message);
     }
@@ -239,9 +223,9 @@ public ExitMessage newExitMessage(final String format, final Object result) {
         final boolean hasFormat = Strings.isNotEmpty(format);
         final Message message;
         if (result == null) {
-            message = hasFormat ? messageFactory.newMessage(format) : null;
+            message = hasFormat ? ParameterizedMessageFactory.INSTANCE.newMessage(format) : null;
         } else {
-            message = messageFactory.newMessage(hasFormat ? format : "with({})", result);
+            message = ParameterizedMessageFactory.INSTANCE.newMessage(hasFormat ? format : "with({})", result);
         }
         return newExitMessage(message);
     }
diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/util/Strings.java b/log4j-api/src/main/java/org/apache/logging/log4j/util/Strings.java
index 8eea0e782c8..bee54324f44 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/util/Strings.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/util/Strings.java
@@ -21,7 +21,6 @@
 import java.util.Iterator;
 import java.util.Locale;
 import java.util.Objects;
-import java.util.Optional;
 
 /**
  * <em>Consider this class private.</em>
@@ -289,19 +288,6 @@ public static String trimToNull(final String str) {
         return isEmpty(ts) ? null : ts;
     }
 
-    /**
-     * Removes control characters from both ends of this String returning {@code Optional.empty()} if the String is
-     * empty ("") after the trim or if it is {@code null}.
-     * @param str The String to trim.
-     * @return An Optional containing the String.
-     *
-     * @see #trimToNull(String)
-     * @since 2.24.0
-     */
-    public static Optional<String> trimToOptional(final String str) {
-        return Optional.ofNullable(str).map(String::trim).filter(s -> !s.isEmpty());
-    }
-
     private Strings() {
         // empty
     }

From a1c2bd1785379d67be05ffd2f2c0e666f714432c Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <piotr.github@karwasz.org>
Date: Fri, 22 Mar 2024 11:43:39 +0100
Subject: [PATCH 10/12] Add changelog for GraalVM-compatibility

---
 src/changelog/.2.x.x/1539_graalvm_friendly.xml | 8 ++++++++
 1 file changed, 8 insertions(+)
 create mode 100644 src/changelog/.2.x.x/1539_graalvm_friendly.xml

diff --git a/src/changelog/.2.x.x/1539_graalvm_friendly.xml b/src/changelog/.2.x.x/1539_graalvm_friendly.xml
new file mode 100644
index 00000000000..74964f43564
--- /dev/null
+++ b/src/changelog/.2.x.x/1539_graalvm_friendly.xml
@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<entry xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+       xmlns="http://logging.apache.org/log4j/changelog"
+       xsi:schemaLocation="http://logging.apache.org/log4j/changelog https://logging.apache.org/log4j/changelog-0.1.3.xsd"
+       type="changed">
+  <issue id="1539" link="https://github.com/apache/logging-log4j2/pull/1539"/>
+  <description format="asciidoc">Fix usage of `log4j-api` in GraalVM without additional reachability data.</description>
+</entry>

From f0e82d15e7f718059ecb4207c6f63396e3fb7421 Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <piotr.github@karwasz.org>
Date: Fri, 22 Mar 2024 11:51:15 +0100
Subject: [PATCH 11/12] Fix BND baseline error

---
 .../java/org/apache/logging/log4j/test/junit/Resources.java     | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/Resources.java b/log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/Resources.java
index 8956311e499..66631c194e6 100644
--- a/log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/Resources.java
+++ b/log4j-api-test/src/main/java/org/apache/logging/log4j/test/junit/Resources.java
@@ -16,11 +16,13 @@
  */
 package org.apache.logging.log4j.test.junit;
 
+import aQute.bnd.annotation.baseline.BaselineIgnore;
 import org.junit.jupiter.api.parallel.ResourceLock;
 
 /**
  * Constants to use the {@link ResourceLock} annotation.
  */
+@BaselineIgnore("2.24.0")
 public final class Resources {
 
     /**

From 11209a3abf4b5eb65cf416c5f22a992357fd45fc Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <piotr.github@karwasz.org>
Date: Fri, 22 Mar 2024 13:20:39 +0100
Subject: [PATCH 12/12] Rollback breaking change in `ReusableMessage`

---
 .../org/apache/logging/log4j/message/ReusableMessage.java | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/log4j-api/src/main/java/org/apache/logging/log4j/message/ReusableMessage.java b/log4j-api/src/main/java/org/apache/logging/log4j/message/ReusableMessage.java
index 5a5d264e680..35e8fa3919c 100644
--- a/log4j-api/src/main/java/org/apache/logging/log4j/message/ReusableMessage.java
+++ b/log4j-api/src/main/java/org/apache/logging/log4j/message/ReusableMessage.java
@@ -18,7 +18,6 @@
 
 import org.apache.logging.log4j.util.PerformanceSensitive;
 import org.apache.logging.log4j.util.StringBuilderFormattable;
-import org.osgi.annotation.versioning.ProviderType;
 
 /**
  * Messages implementing this interface are reused between logging calls.
@@ -30,7 +29,6 @@
  * @since 2.6
  */
 @PerformanceSensitive("allocation")
-@ProviderType
 public interface ReusableMessage extends Message, StringBuilderFormattable {
 
     /**
@@ -71,10 +69,4 @@ public interface ReusableMessage extends Message, StringBuilderFormattable {
      * @return an immutable snapshot of this message
      */
     Message memento();
-
-    /**
-     * Resets the object to a clean state.
-     * @since 2.24.0
-     */
-    void clear();
 }