Added CachingWebAppClassLoader

jetty-webapp/src/main/java/org/eclipse/jetty/webapp/CachingWebAppClassLoader.java

@@ -0,0 +1,121 @@
+//
+//  ========================================================================
+//  Copyright (c) 1995-2015 Mort Bay Consulting Pty. Ltd.
+//  ------------------------------------------------------------------------
+//  All rights reserved. This program and the accompanying materials
+//  are made available under the terms of the Eclipse Public License v1.0
+//  and Apache License v2.0 which accompanies this distribution.
+//
+//      The Eclipse Public License is available at
+//      http://www.eclipse.org/legal/epl-v10.html
+//
+//      The Apache License v2.0 is available at
+//      http://www.opensource.org/licenses/apache2.0.php
+//
+//  You may elect to redistribute this code under either of these licenses.
+//  ========================================================================
+//
+
+package org.eclipse.jetty.webapp;
+
+import java.io.IOException;
+import java.net.URL;
+import java.util.concurrent.ConcurrentHashMap;
+
+import org.eclipse.jetty.util.ConcurrentHashSet;
+import org.eclipse.jetty.util.annotation.ManagedObject;
+import org.eclipse.jetty.util.annotation.ManagedOperation;
+
+
+/**
+ * A WebAppClassLoader that caches {@link #getResource(String)} results.
+ * Specifically this ClassLoader caches not found classes and resources,
+ * which can greatly increase performance for applications that search 
+ * for resources.
+ */
+@ManagedObject
+public class CachingWebAppClassLoader extends WebAppClassLoader
+{
+    private final ConcurrentHashSet<String> _notFound = new ConcurrentHashSet<>();
+    private final ConcurrentHashMap<String,URL> _cache = new ConcurrentHashMap<>();
+    
+    public CachingWebAppClassLoader(ClassLoader parent, Context context) throws IOException
+    {
+        super(parent,context);
+    }
+
+    public CachingWebAppClassLoader(Context context) throws IOException
+    {
+        super(context);
+    }
+
+    @Override
+    public URL getResource(String name)
+    {
+        if (_notFound.contains(name))
+            return null;
+        
+        URL url = _cache.get(name);
+        
+        if (name==null)
+        {
+            url = super.getResource(name);
+        
+            if (url==null)
+            {
+                _notFound.add(name);
+            }
+            else
+            {
+                _cache.putIfAbsent(name,url);
+            }
+        }
+        
+        return url;
+    }
+
+    @Override
+    protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException
+    {
+        if (_notFound.contains(name))
+            throw new ClassNotFoundException(name+": in notfound cache");
+        try
+        {
+            return super.loadClass(name,resolve);
+        }
+        catch (ClassNotFoundException nfe)
+        {
+            _notFound.add(name);
+            throw nfe; 
+        }
+    }
+
+    @Override
+    protected Class<?> findClass(String name) throws ClassNotFoundException
+    {
+        if (_notFound.contains(name))
+            throw new ClassNotFoundException(name+": in notfound cache");
+        try
+        {
+            return super.findClass(name);
+        }
+        catch (ClassNotFoundException nfe)
+        {
+            _notFound.add(name);
+            throw nfe; 
+        }
+    }
+
+    @ManagedOperation
+    public void clearCache()
+    {
+        _cache.clear();
+        _notFound.clear();
+    }
+    
+    @Override
+    public String toString()
+    {
+        return "Caching["+super.toString()+"]";
+    }
+}