added MultiParentClassLoader

scm-webapp/src/main/java/sonia/scm/plugin/MultiParentClassLoader.java

@@ -0,0 +1,171 @@
+/**
+ * Copyright (c) 2010, Sebastian Sdorra All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer. 2. Redistributions in
+ * binary form must reproduce the above copyright notice, this list of
+ * conditions and the following disclaimer in the documentation and/or other
+ * materials provided with the distribution. 3. Neither the name of SCM-Manager;
+ * nor the names of its contributors may be used to endorse or promote products
+ * derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * http://bitbucket.org/sdorra/scm-manager
+ *
+ */
+
+
+
+package sonia.scm.plugin;
+
+//~--- JDK imports ------------------------------------------------------------
+
+import java.io.IOException;
+
+import java.net.URL;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Enumeration;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+/**
+ * TODO add caching
+ *
+ * @author Sebastian Sdorra
+ */
+public class MultiParentClassLoader extends ClassLoader
+{
+
+  /**
+   * Constructs ...
+   *
+   *
+   * @param parents
+   */
+  public MultiParentClassLoader(ClassLoader... parents)
+  {
+    this(Arrays.asList(parents));
+  }
+
+  /**
+   * Constructs ...
+   *
+   *
+   * @param parents
+   */
+  public MultiParentClassLoader(Collection<? extends ClassLoader> parents)
+  {
+    super(null);
+    this.parents = new CopyOnWriteArrayList<>(parents);
+  }
+
+  //~--- get methods ----------------------------------------------------------
+
+  /**
+   * Method description
+   *
+   *
+   * @param name
+   *
+   * @return
+   */
+  @Override
+  public URL getResource(String name)
+  {
+    for (ClassLoader parent : parents)
+    {
+      URL resource = parent.getResource(name);
+
+      if (resource != null)
+      {
+        return resource;
+      }
+    }
+
+    return null;
+  }
+
+  /**
+   * Method description
+   *
+   *
+   * @param name
+   *
+   * @return
+   *
+   * @throws IOException
+   */
+  @Override
+  public Enumeration<URL> getResources(String name) throws IOException
+  {
+    Set<URL> resources = new LinkedHashSet<>();
+
+    for (ClassLoader parent : parents)
+    {
+      Enumeration<URL> parentResources = parent.getResources(name);
+
+      while (parentResources.hasMoreElements())
+      {
+        resources.add(parentResources.nextElement());
+      }
+    }
+
+    return Collections.enumeration(resources);
+  }
+
+  //~--- methods --------------------------------------------------------------
+
+  /**
+   * Method description
+   *
+   *
+   * @param name
+   * @param resolve
+   *
+   * @return
+   *
+   * @throws ClassNotFoundException
+   */
+  @Override
+  protected Class<?> loadClass(String name, boolean resolve)
+    throws ClassNotFoundException
+  {
+    for (ClassLoader parent : parents)
+    {
+      try
+      {
+        return parent.loadClass(name);
+      }
+      catch (ClassNotFoundException e)
+      {
+
+        // Expected
+      }
+    }
+
+    throw new ClassNotFoundException(String.format("%s not found.", name));
+  }
+
+  //~--- fields ---------------------------------------------------------------
+
+  /** Field description */
+  private final List<ClassLoader> parents;
+}