SONAR-1838: Allow inter-dependencies for plugins

1 files changed, 100 insertions, 0 deletions

diff --git a/sonar-core/src/main/java/org/sonar/core/classloaders/ClassLoadersCollection.java b/sonar-core/src/main/java/org/sonar/core/classloaders/ClassLoadersCollection.java
new file mode 100644
index 00000000000..858ed05f88b
--- /dev/null
+++ b/sonar-core/src/main/java/org/sonar/core/classloaders/ClassLoadersCollection.java
@@ -0,0 +1,100 @@
+package org.sonar.core.classloaders;
+
+import org.apache.commons.lang.StringUtils;
+import org.codehaus.classworlds.ClassRealm;
+import org.codehaus.classworlds.ClassWorld;
+import org.codehaus.classworlds.DuplicateRealmException;
+import org.codehaus.classworlds.NoSuchRealmException;
+import org.sonar.api.utils.Logs;
+import org.sonar.api.utils.SonarException;
+
+import java.net.URL;
+import java.util.Arrays;
+import java.util.Collection;
+
+/**
+ * EXPERIMENTAL!
+ * 
+ * Encapsulates manipulations with ClassLoaders, such as creation and establishing dependencies.
+ * Current implementation based on {@link ClassWorld}.
+ * 
+ * <h3>IMPORTANT</h3>
+ * <ul>
+ * <li>If we have pluginA , then all classes and resources from packages and subpackages of org.sonar.plugins.pluginA will be visible for
+ * all other plugins.</li>
+ * <li>If pluginA depends on lib.jar which contains org.sonar.plugins.pluginA.SomeClass , then SomeClass will be visible for all other
+ * plugins.</li>
+ * </ul>
+ * 
+ * @since 2.4
+ */
+public class ClassLoadersCollection {
+
+  private static final String EXPORTED_PREFIX = "org.sonar.plugins.";
+
+  private ClassWorld world = new ClassWorld();
+  private ClassLoader baseClassLoader;
+
+  public ClassLoadersCollection(ClassLoader baseClassLoader) {
+    this.baseClassLoader = baseClassLoader;
+  }
+
+  /**
+   * Generates URLClassLoaders, which use the parent first delegation mode.
+   * Actually this method shouldn't return anything, because dependencies must be established - see {@link #done()}.
+   */
+  public ClassLoader createClassLoader(String key, Collection<URL> urls) {
+    try {
+      ClassRealm realm = world.newRealm(key, baseClassLoader);
+      for (URL constituent : urls) {
+        realm.addConstituent(constituent);
+      }
+      // export(realm, EXPORTED_PREFIX + key);
+      return realm.getClassLoader();
+    } catch (DuplicateRealmException e) {
+      throw new SonarException(e);
+    }
+  }
+
+  /**
+   * Establishes dependencies among ClassLoaders.
+   */
+  public void done() {
+    for (Object o : world.getRealms()) {
+      ClassRealm realm = (ClassRealm) o;
+      export(realm, EXPORTED_PREFIX + realm.getId());
+    }
+  }
+
+  /**
+   * Exports specified packages from given ClassRealm to all others.
+   */
+  private void export(ClassRealm realm, String... packages) {
+    Logs.INFO.info("Exporting " + Arrays.toString(packages) + " from " + realm.getId());
+    for (Object o : world.getRealms()) {
+      ClassRealm dep = (ClassRealm) o;
+      if ( !StringUtils.equals(dep.getId(), realm.getId())) {
+        try {
+          for (String packageName : packages) {
+            dep.importFrom(realm.getId(), packageName);
+          }
+        } catch (NoSuchRealmException e) {
+          // should never happen
+          throw new SonarException(e);
+        }
+      }
+    }
+  }
+
+  /**
+   * Note that this method should be called only after creation of all ClassLoaders - see {@link #done()}.
+   */
+  public ClassLoader get(String key) {
+    try {
+      return world.getRealm(key).getClassLoader();
+    } catch (NoSuchRealmException e) {
+      return null;
+    }
+  }
+
+}