refactor: plugin resource loading to only load from plugin itself ins…

…tead of delegating to core

application/src/main/java/run/halo/app/plugin/DefaultPluginClassLoader.java

@@ -0,0 +1,40 @@
+package run.halo.app.plugin;
+
+import java.io.IOException;
+import java.net.URL;
+import java.util.Enumeration;
+import lombok.extern.slf4j.Slf4j;
+import org.pf4j.ClassLoadingStrategy;
+import org.pf4j.PluginClassLoader;
+import org.pf4j.PluginDescriptor;
+import org.pf4j.PluginManager;
+
+/**
+ * <p>Plugin manager should create one instance of this class for every available plugin. By
+ * default, this class loader is a Parent First ClassLoader - it loads the classes from the
+ * parent class loader before loads from the plugin. Use classLoadingStrategy to change
+ * the loading strategy.</p>
+ * <p>By default, this class loader loads the resources from the plugin only - if the resource not
+ * found in the plugin, it returns null.</p>
+ *
+ * @author guqing
+ * @since 2.10.0
+ */
+@Slf4j
+public class DefaultPluginClassLoader extends PluginClassLoader {
+    public DefaultPluginClassLoader(PluginManager pluginManager, PluginDescriptor pluginDescriptor,
+        ClassLoader parent) {
+        super(pluginManager, pluginDescriptor, parent, ClassLoadingStrategy.APD);
+    }
+
+    @Override
+    public URL getResource(String name) {
+        log.trace("Received request to load resource '{}'", name);
+        return this.findResource(name);
+    }
+
+    @Override
+    public Enumeration<URL> getResources(String name) throws IOException {
+        return this.findResources(name);
+    }
+}

application/src/main/java/run/halo/app/plugin/PluginAutoConfiguration.java

@@ -9,7 +9,6 @@
 import java.time.Instant;
 import lombok.extern.slf4j.Slf4j;
 import org.apache.commons.lang3.StringUtils;
-import org.pf4j.ClassLoadingStrategy;
 import org.pf4j.CompoundPluginLoader;
 import org.pf4j.CompoundPluginRepository;
 import org.pf4j.DefaultPluginRepository;
@@ -114,8 +113,8 @@ protected PluginLoader createPluginLoader() {
                                 @Override
                                 protected PluginClassLoader createPluginClassLoader(Path pluginPath,
                                     PluginDescriptor pluginDescriptor) {
-                                    return new PluginClassLoader(pluginManager, pluginDescriptor,
-                                        getClass().getClassLoader(), ClassLoadingStrategy.APD);
+                                    return new DefaultPluginClassLoader(pluginManager,
+                                        pluginDescriptor, getClass().getClassLoader());
                                 }
 
                                 @Override
@@ -141,8 +140,8 @@ public ClassLoader loadPlugin(Path pluginPath,
                                 public ClassLoader loadPlugin(Path pluginPath,
                                     PluginDescriptor pluginDescriptor) {
                                     PluginClassLoader pluginClassLoader =
-                                        new PluginClassLoader(pluginManager, pluginDescriptor,
-                                            getClass().getClassLoader(), ClassLoadingStrategy.APD);
+                                        new DefaultPluginClassLoader(pluginManager,
+                                            pluginDescriptor, getClass().getClassLoader());
                                     pluginClassLoader.addFile(pluginPath.toFile());
                                     return pluginClassLoader;