Switch to JSpecify annotations

This commit updates the whole Spring Framework codebase to use JSpecify
annotations instead of Spring null-safety annotations with JSR 305
semantics.

JSpecify provides signficant enhancements such as properly defined
specifications, a canonical dependency with no split-package issue,
better tooling, better Kotlin integration and the capability to specify
generic type, array and varargs element null-safety. Generic type
null-safety is not defined by this commit yet and will be specified
later.

A key difference is that Spring null-safety annotations, following
JSR 305 semantics, apply to fields, parameters and return values,
while JSpecify annotations apply to type usages. That's why this
commit moves nullability annotations closer to the type for fields
and return values.

See spring-projectsgh-28797

framework-docs/src/main/kotlin/org/springframework/docs/integration/cache/cachestoreconfigurationcaffeine/CustomCacheConfiguration.kt

@@ -28,9 +28,7 @@ class CustomCacheConfiguration {
 	// tag::snippet[]
 	@Bean
 	fun cacheManager(): CacheManager {
-		return CaffeineCacheManager().apply {
-			cacheNames = listOf("default", "books")
-		}
+		return CaffeineCacheManager("default", "books")
 	}
 	// end::snippet[]
 }

framework-platform/framework-platform.gradle

@@ -131,6 +131,7 @@ dependencies {
 		api("org.htmlunit:htmlunit:4.6.0")
 		api("org.javamoney:moneta:1.4.4")
 		api("org.jruby:jruby:9.4.9.0")
+		api("org.jspecify:jspecify:1.0.0")
 		api("org.junit.support:testng-engine:1.0.5")
 		api("org.mozilla:rhino:1.7.15")
 		api("org.ogce:xpp3:1.1.6")

gradle/spring-module.gradle

@@ -13,8 +13,8 @@ dependencies {
 	jmh 'org.openjdk.jmh:jmh-generator-annprocess:1.37'
 	jmh 'org.openjdk.jmh:jmh-generator-bytecode:1.37'
 	jmh 'net.sf.jopt-simple:jopt-simple'
-	errorprone 'com.uber.nullaway:nullaway:0.10.26'
-	errorprone 'com.google.errorprone:error_prone_core:2.9.0'
+	errorprone 'com.uber.nullaway:nullaway:0.12.2'
+	errorprone 'com.google.errorprone:error_prone_core:2.35.1'
 }
 
 pluginManager.withPlugin("kotlin") {

integration-tests/src/test/java/org/springframework/aop/framework/autoproxy/AdvisorAutoProxyCreatorIntegrationTests.java

@@ -20,6 +20,7 @@
 import java.util.List;
 
 import jakarta.servlet.ServletException;
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.aop.support.AopUtils;
@@ -31,7 +32,6 @@
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.beans.testfixture.beans.ITestBean;
 import org.springframework.context.support.ClassPathXmlApplicationContext;
-import org.springframework.lang.Nullable;
 import org.springframework.transaction.NoTransactionException;
 import org.springframework.transaction.interceptor.TransactionInterceptor;
 import org.springframework.transaction.testfixture.CallCountingTransactionManager;

spring-aop/src/main/java/org/springframework/aop/AfterReturningAdvice.java

@@ -18,7 +18,7 @@
 
 import java.lang.reflect.Method;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * After returning advice is invoked only on normal method return, not if an

spring-aop/src/main/java/org/springframework/aop/MethodBeforeAdvice.java

@@ -18,7 +18,7 @@
 
 import java.lang.reflect.Method;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Advice invoked before a method is invoked. Such advices cannot

spring-aop/src/main/java/org/springframework/aop/ProxyMethodInvocation.java

@@ -17,8 +17,7 @@
 package org.springframework.aop;
 
 import org.aopalliance.intercept.MethodInvocation;
-
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Extension of the AOP Alliance {@link org.aopalliance.intercept.MethodInvocation}
@@ -83,7 +82,6 @@ public interface ProxyMethodInvocation extends MethodInvocation {
 	 * @return the value of the attribute, or {@code null} if not set
 	 * @see #setUserAttribute
 	 */
-	@Nullable
-	Object getUserAttribute(String key);
+	@Nullable Object getUserAttribute(String key);
 
 }

spring-aop/src/main/java/org/springframework/aop/TargetClassAware.java

@@ -16,7 +16,7 @@
 
 package org.springframework.aop;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Minimal interface for exposing the target class behind a proxy.
@@ -36,7 +36,6 @@ public interface TargetClassAware {
 	 * (typically a proxy configuration or an actual proxy).
 	 * @return the target Class, or {@code null} if not known
 	 */
-	@Nullable
-	Class<?> getTargetClass();
+	@Nullable Class<?> getTargetClass();
 
 }

spring-aop/src/main/java/org/springframework/aop/TargetSource.java

@@ -16,7 +16,7 @@
 
 package org.springframework.aop;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * A {@code TargetSource} is used to obtain the current "target" of
@@ -42,8 +42,7 @@ public interface TargetSource extends TargetClassAware {
 	 * @return the type of targets returned by this {@link TargetSource}
 	 */
 	@Override
-	@Nullable
-	Class<?> getTargetClass();
+	@Nullable Class<?> getTargetClass();
 
 	/**
 	 * Will all calls to {@link #getTarget()} return the same object?
@@ -64,8 +63,7 @@ default boolean isStatic() {
 	 * or {@code null} if there is no actual target instance
 	 * @throws Exception if the target object can't be resolved
 	 */
-	@Nullable
-	Object getTarget() throws Exception;
+	@Nullable Object getTarget() throws Exception;
 
 	/**
 	 * Release the given target object obtained from the

spring-aop/src/main/java/org/springframework/aop/aspectj/AbstractAspectJAdvice.java

@@ -31,6 +31,7 @@
 import org.aspectj.lang.ProceedingJoinPoint;
 import org.aspectj.weaver.tools.JoinPointMatch;
 import org.aspectj.weaver.tools.PointcutParameter;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.aop.AopInvocationException;
 import org.springframework.aop.MethodMatcher;
@@ -42,7 +43,6 @@
 import org.springframework.aop.support.StaticMethodMatcher;
 import org.springframework.core.DefaultParameterNameDiscoverer;
 import org.springframework.core.ParameterNameDiscoverer;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.CollectionUtils;
@@ -118,16 +118,13 @@ public static JoinPoint currentJoinPoint() {
 	 * This will be non-null if the creator of this advice object knows the argument names
 	 * and sets them explicitly.
 	 */
-	@Nullable
-	private String[] argumentNames;
+	private @Nullable String @Nullable [] argumentNames;
 
 	/** Non-null if after throwing advice binds the thrown value. */
-	@Nullable
-	private String throwingName;
+	private @Nullable String throwingName;
 
 	/** Non-null if after returning advice binds the return value. */
-	@Nullable
-	private String returningName;
+	private @Nullable String returningName;
 
 	private Class<?> discoveredReturningType = Object.class;
 
@@ -145,13 +142,11 @@ public static JoinPoint currentJoinPoint() {
 	 */
 	private int joinPointStaticPartArgumentIndex = -1;
 
-	@Nullable
-	private Map<String, Integer> argumentBindings;
+	private @Nullable Map<String, Integer> argumentBindings;
 
 	private boolean argumentsIntrospected = false;
 
-	@Nullable
-	private Type discoveredReturningGenericType;
+	private @Nullable Type discoveredReturningGenericType;
 	// Note: Unlike return type, no such generic information is needed for the throwing type,
 	// since Java doesn't allow exception types to be parameterized.
 
@@ -212,8 +207,7 @@ public final AspectInstanceFactory getAspectInstanceFactory() {
 	/**
 	 * Return the ClassLoader for aspect instances.
 	 */
-	@Nullable
-	public final ClassLoader getAspectClassLoader() {
+	public final @Nullable ClassLoader getAspectClassLoader() {
 		return this.aspectInstanceFactory.getAspectClassLoader();
 	}
 
@@ -318,8 +312,7 @@ protected Class<?> getDiscoveredReturningType() {
 		return this.discoveredReturningType;
 	}
 
-	@Nullable
-	protected Type getDiscoveredReturningGenericType() {
+	protected @Nullable Type getDiscoveredReturningGenericType() {
 		return this.discoveredReturningGenericType;
 	}
 
@@ -657,8 +650,7 @@ protected JoinPoint getJoinPoint() {
 	/**
 	 * Get the current join point match at the join point we are being dispatched on.
 	 */
-	@Nullable
-	protected JoinPointMatch getJoinPointMatch() {
+	protected @Nullable JoinPointMatch getJoinPointMatch() {
 		MethodInvocation mi = ExposeInvocationInterceptor.currentInvocation();
 		if (!(mi instanceof ProxyMethodInvocation pmi)) {
 			throw new IllegalStateException("MethodInvocation is not a Spring ProxyMethodInvocation: " + mi);
@@ -672,8 +664,7 @@ protected JoinPointMatch getJoinPointMatch() {
 	// 'last man wins' which is not what we want at all.
 	// Using the expression is guaranteed to be safe, since 2 identical expressions
 	// are guaranteed to bind in exactly the same way.
-	@Nullable
-	protected JoinPointMatch getJoinPointMatch(ProxyMethodInvocation pmi) {
+	protected @Nullable JoinPointMatch getJoinPointMatch(ProxyMethodInvocation pmi) {
 		String expression = this.pointcut.getExpression();
 		return (expression != null ? (JoinPointMatch) pmi.getUserAttribute(expression) : null);
 	}

spring-aop/src/main/java/org/springframework/aop/aspectj/AspectInstanceFactory.java

@@ -16,8 +16,9 @@
 
 package org.springframework.aop.aspectj;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.core.Ordered;
-import org.springframework.lang.Nullable;
 
 /**
  * Interface implemented to provide an instance of an AspectJ aspect.
@@ -44,7 +45,6 @@ public interface AspectInstanceFactory extends Ordered {
 	 * @return the aspect class loader (or {@code null} for the bootstrap loader)
 	 * @see org.springframework.util.ClassUtils#getDefaultClassLoader()
 	 */
-	@Nullable
-	ClassLoader getAspectClassLoader();
+	@Nullable ClassLoader getAspectClassLoader();
 
 }

spring-aop/src/main/java/org/springframework/aop/aspectj/AspectJAdviceParameterNameDiscoverer.java

@@ -28,9 +28,9 @@
 import org.aspectj.lang.ProceedingJoinPoint;
 import org.aspectj.weaver.tools.PointcutParser;
 import org.aspectj.weaver.tools.PointcutPrimitive;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.core.ParameterNameDiscoverer;
-import org.springframework.lang.Nullable;
 import org.springframework.util.StringUtils;
 
 /**
@@ -157,22 +157,19 @@ public class AspectJAdviceParameterNameDiscoverer implements ParameterNameDiscov
 
 
 	/** The pointcut expression associated with the advice, as a simple String. */
-	@Nullable
-	private final String pointcutExpression;
+	private final @Nullable String pointcutExpression;
 
 	private boolean raiseExceptions;
 
 	/** If the advice is afterReturning, and binds the return value, this is the parameter name used. */
-	@Nullable
-	private String returningName;
+	private @Nullable String returningName;
 
 	/** If the advice is afterThrowing, and binds the thrown value, this is the parameter name used. */
-	@Nullable
-	private String throwingName;
+	private @Nullable String throwingName;
 
 	private Class<?>[] argumentTypes = new Class<?>[0];
 
-	private String[] parameterNameBindings = new String[0];
+	private @Nullable String[] parameterNameBindings = new String[0];
 
 	private int numberOfRemainingUnboundArguments;
 
@@ -221,8 +218,7 @@ public void setThrowingName(@Nullable String throwingName) {
 	 * @return the parameter names
 	 */
 	@Override
-	@Nullable
-	public String[] getParameterNames(Method method) {
+	public @Nullable String @Nullable [] getParameterNames(Method method) {
 		this.argumentTypes = method.getParameterTypes();
 		this.numberOfRemainingUnboundArguments = this.argumentTypes.length;
 		this.parameterNameBindings = new String[this.numberOfRemainingUnboundArguments];
@@ -289,8 +285,7 @@ public String[] getParameterNames(Method method) {
 	 * {@link #setRaiseExceptions(boolean) raiseExceptions} has been set to {@code true}
 	 */
 	@Override
-	@Nullable
-	public String[] getParameterNames(Constructor<?> ctor) {
+	public String @Nullable [] getParameterNames(Constructor<?> ctor) {
 		if (this.raiseExceptions) {
 			throw new UnsupportedOperationException("An advice method can never be a constructor");
 		}
@@ -453,8 +448,7 @@ else if (numAnnotationSlots == 1) {
 	/**
 	 * If the token starts meets Java identifier conventions, it's in.
 	 */
-	@Nullable
-	private String maybeExtractVariableName(@Nullable String candidateToken) {
+	private @Nullable String maybeExtractVariableName(@Nullable String candidateToken) {
 		if (AspectJProxyUtils.isVariableName(candidateToken)) {
 			return candidateToken;
 		}

spring-aop/src/main/java/org/springframework/aop/aspectj/AspectJAfterAdvice.java

@@ -21,9 +21,9 @@
 
 import org.aopalliance.intercept.MethodInterceptor;
 import org.aopalliance.intercept.MethodInvocation;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.aop.AfterAdvice;
-import org.springframework.lang.Nullable;
 
 /**
  * Spring AOP advice wrapping an AspectJ after advice method.
@@ -43,8 +43,7 @@ public AspectJAfterAdvice(
 
 
 	@Override
-	@Nullable
-	public Object invoke(MethodInvocation mi) throws Throwable {
+	public @Nullable Object invoke(MethodInvocation mi) throws Throwable {
 		try {
 			return mi.proceed();
 		}

spring-aop/src/main/java/org/springframework/aop/aspectj/AspectJAfterReturningAdvice.java

@@ -20,9 +20,10 @@
 import java.lang.reflect.Method;
 import java.lang.reflect.Type;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.aop.AfterAdvice;
 import org.springframework.aop.AfterReturningAdvice;
-import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.TypeUtils;
 

spring-aop/src/main/java/org/springframework/aop/aspectj/AspectJAfterThrowingAdvice.java

@@ -21,9 +21,9 @@
 
 import org.aopalliance.intercept.MethodInterceptor;
 import org.aopalliance.intercept.MethodInvocation;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.aop.AfterAdvice;
-import org.springframework.lang.Nullable;
 
 /**
  * Spring AOP advice wrapping an AspectJ after-throwing advice method.
@@ -58,8 +58,7 @@ public void setThrowingName(String name) {
 	}
 
 	@Override
-	@Nullable
-	public Object invoke(MethodInvocation mi) throws Throwable {
+	public @Nullable Object invoke(MethodInvocation mi) throws Throwable {
 		try {
 			return mi.proceed();
 		}

spring-aop/src/main/java/org/springframework/aop/aspectj/AspectJAopUtils.java

@@ -17,11 +17,11 @@
 package org.springframework.aop.aspectj;
 
 import org.aopalliance.aop.Advice;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.aop.Advisor;
 import org.springframework.aop.AfterAdvice;
 import org.springframework.aop.BeforeAdvice;
-import org.springframework.lang.Nullable;
 
 /**
  * Utility methods for dealing with AspectJ advisors.
@@ -59,8 +59,7 @@ public static boolean isAfterAdvice(Advisor anAdvisor) {
 	 * If neither the advisor nor the advice have precedence information, this method
 	 * will return {@code null}.
 	 */
-	@Nullable
-	public static AspectJPrecedenceInformation getAspectJPrecedenceInformationFor(Advisor anAdvisor) {
+	public static @Nullable AspectJPrecedenceInformation getAspectJPrecedenceInformationFor(Advisor anAdvisor) {
 		if (anAdvisor instanceof AspectJPrecedenceInformation ajpi) {
 			return ajpi;
 		}