🐛 Refactor plugin class loading to use custom PluginsClassloader. Thi…

…s change ensures that plugin classes are consistently loaded by a single classloader, preventing conflicts arising from classes being loaded by multiple classloaders.

core/src/main/java/org/restheart/plugins/PluginsClassloader.java

@@ -0,0 +1,79 @@
+/*-
+ * ========================LICENSE_START=================================
+ * restheart-core
+ * %%
+ * Copyright (C) 2014 - 2024 SoftInstigate
+ * %%
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ * =========================LICENSE_END==================================
+ */
+package org.restheart.plugins;
+
+import java.io.IOException;
+import java.net.URL;
+import java.net.URLClassLoader;
+
+/**
+ * Loads a class, including searching within all plugin JAR files.
+ * <p>
+ * This method is essential for the {@code collectFieldInjections()} method, which processes field injections
+ * annotated with {@code @Inject}. Specifically, it addresses cases where the {@code @Inject} annotation
+ * references a {@link org.restheart.plugins.Provider} that returns an object. The class of this object may reside
+ * in a plugin JAR file, necessitating a comprehensive search to locate and load the class correctly.
+ * </p>
+ */
+public class PluginsClassloader extends ClassLoader {
+    private static PluginsClassloader SINGLETON = null;
+
+    /**
+     * call after PluginsScanner.jars array is populated
+     * @param jars
+     */
+    public static void init(URL[] jars) {
+        if (SINGLETON != null) {
+            throw new IllegalStateException("already initialized");
+        } else {
+            try {
+                SINGLETON = new PluginsClassloader(jars);
+            } catch(IOException ioe) {
+                throw new RuntimeException("error initializing", ioe);
+            }
+        }
+    }
+
+    private final URLClassLoader pluginsClassLoader;
+
+    private PluginsClassloader(URL[] jars) throws IOException {
+        this.pluginsClassLoader = new URLClassLoader(jars);
+    }
+
+    public static PluginsClassloader getInstance() {
+        if (SINGLETON == null) {
+            throw new IllegalStateException("not initialized");
+        } else {
+            return SINGLETON;
+        }
+    }
+
+    @Override
+    public Class<?> loadClass(String name) throws ClassNotFoundException {
+        try {
+            // use the current classloader
+            return this.getClass().getClassLoader().loadClass(name);
+        } catch (ClassNotFoundException cnfe) {
+            // look in the plugins jars
+            return this.pluginsClassLoader.loadClass(name);
+        }
+    }
+}

core/src/main/java/org/restheart/plugins/PluginsFactory.java

@@ -23,7 +23,6 @@
 import static org.restheart.configuration.Utils.getOrDefault;
 
 import java.lang.reflect.InvocationTargetException;
-import java.net.URLClassLoader;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.LinkedHashSet;
@@ -56,15 +55,7 @@ public static PluginsFactory getInstance() {
         return SINGLETON;
     }
 
-    private final ArrayList<ClassLoader> classLoaders = new ArrayList<>();
-
     private PluginsFactory() {
-        classLoaders.add(this.getClass().getClassLoader());
-
-        // take classloaders from PluginsScanner into account
-        if (PluginsScanner.jars != null) {
-            classLoaders.add(new URLClassLoader(PluginsScanner.jars));
-        }
     }
 
     private Set<PluginRecord<AuthMechanism>> authMechanismsCache = null;
@@ -283,18 +274,7 @@ private Class<Plugin> loadPluginClass(PluginDescriptor plugin) throws ClassNotFo
             return PC_CACHE.get(plugin.clazz());
         }
 
-        for (var classLoader : this.classLoaders) {
-            try {
-                var pluginc = (Class<Plugin>) classLoader.loadClass(plugin.clazz());
-
-                PC_CACHE.put(plugin.clazz(), pluginc);
-                return pluginc;
-            } catch (ClassNotFoundException cnfe) {
-                // nothing to do
-            }
-        }
-
-        throw new ClassNotFoundException("plugin class not found " + plugin.clazz());
+        return (Class<Plugin>) PluginsClassloader.getInstance().loadClass(plugin.clazz());
     }
 
     private Plugin instantiatePlugin(Class<Plugin> pc, String pluginType, String pluginName, Configuration conf) throws InstantiationException, IllegalAccessException, InvocationTargetException, IllegalArgumentException, SecurityException, ClassNotFoundException {

core/src/main/java/org/restheart/plugins/PluginsScanner.java

@@ -45,7 +45,6 @@
 import java.util.stream.Collectors;
 import java.util.AbstractMap;
 
-import org.checkerframework.common.returnsreceiver.qual.This;
 import org.restheart.Bootstrapper;
 import org.restheart.graal.NativeImageBuildTimeChecker;
 import org.restheart.plugins.security.AuthMechanism;
@@ -300,7 +299,7 @@ private static ArrayList<InjectionDescriptor> collectFieldInjections(ClassInfo p
                 }
 
                 try {
-                    var fieldClass = loadClass(fi.getTypeDescriptor().toString());
+                    var fieldClass = PluginsClassloader.getInstance().loadClass(fi.getTypeDescriptor().toString());
                     ret.add(new FieldInjectionDescriptor(fi.getName(), fieldClass, annotationParams, fi.hashCode()));
                 } catch(ClassNotFoundException cnfe) {
                     // should not happen
@@ -312,39 +311,6 @@ private static ArrayList<InjectionDescriptor> collectFieldInjections(ClassInfo p
         return ret;
     }
 
-    private static ArrayList<ClassLoader> _classLoaders = null;
-
-    /**
-     * Loads a class, including searching within all plugin JAR files.
-     * <p>
-     * This method is essential for the {@code collectFieldInjections()} method, which processes field injections
-     * annotated with {@code @Inject}. Specifically, it addresses cases where the {@code @Inject} annotation
-     * references a {@link org.restheart.plugins.Provider} that returns an object. The class of this object may reside
-     * in a plugin JAR file, necessitating a comprehensive search to locate and load the class correctly.
-     * </p>
-     */
-    private static Class<?> loadClass(String clazz) throws ClassNotFoundException {
-        if (_classLoaders == null || _classLoaders.isEmpty()) {
-            _classLoaders = new ArrayList<>();
-            _classLoaders.add(PluginsScanner.class.getClassLoader());
-
-            // take all classloaders into account to search also within all plugin JAR files
-            if (PluginsScanner.jars != null) {
-                _classLoaders.add(new URLClassLoader(PluginsScanner.jars));
-            }
-        }
-
-        for (var classLoader: _classLoaders) {
-            try {
-                return Class.forName(clazz, false, classLoader);
-            } catch (ClassNotFoundException cnfe) {
-                // nothing to do
-            }
-        }
-
-        throw new ClassNotFoundException("plugin class not found " + clazz);
-    }
-
     /**
      * this removes the reference to scanResult in the annotation info
      * otherwise the huge object won't be garbage collected
@@ -373,6 +339,8 @@ public RuntimeClassGraph() {
             this.jars = findPluginsJars(pdir);
 
             if (jars != null && jars.length != 0) {
+                PluginsClassloader.init(jars);
+
                 this.classGraph = new ClassGraph().disableModuleScanning().disableDirScanning()
                     .disableNestedJarScanning().disableRuntimeInvisibleAnnotations()
                     .addClassLoader(new URLClassLoader(jars)).addClassLoader(ClassLoader.getSystemClassLoader())

core/src/test/java/org/restheart/plugins/PluginsTest.java

@@ -21,6 +21,8 @@
 
 package org.restheart.plugins;
 
+import java.net.URL;
+
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.mockito.Mockito.mockStatic;
@@ -121,6 +123,7 @@ public void validProviders() {
     }
 
     private static MockedStatic<PluginsScanner> mockPluginsScanner(List<PluginDescriptor> providerDescriptors) {
+        PluginsClassloader.init(new URL[0]);
         var scanner = mockStatic(PluginsScanner.class);
         scanner.when(PluginsScanner::providers).thenReturn(providerDescriptors);
         return scanner;
@@ -204,7 +207,7 @@ private static List<PluginDescriptor> providerDescriptors() {
 
         var iC2 = new ArrayList<InjectionDescriptor>();
         var apC2 = new ArrayList<AbstractMap.SimpleEntry<String, Object>>();
-        apC2.add(new AbstractMap.SimpleEntry<String, Object>("value", "c1"));
+        apC2.add(new AbstractMap.SimpleEntry<>("value", "c1"));
         iC2.add(new FieldInjectionDescriptor("s", String.class, apC2, 8));
 
         var providerDescriptors = new ArrayList<PluginDescriptor>();