cocoon-servlet-service-impl/cocoon-servlet-service-impl-1.2.0/src/main/java/org/apache/cocoon/servletservice/DynamicProxyRequestHandler.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.cocoon.servletservice;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;

import javax.servlet.http.HttpServletRequest;

/**
 * A dynamic wrapper for servlet requests that overwrites the
 * getContextPath, getServletPath and getPathInfo methods to
 * reflect the mount path of the block servlet.
 *
 * @version $Id$
 * @since 1.0.0
 */
public class DynamicProxyRequestHandler implements InvocationHandler {
    private final HttpServletRequest wrapped;
    private final String mountPath;

    private static final Method getContextPathMethod;
    private static final Method getServletPathMethod;
    private static final Method getPathInfoMethod;

    static {
        getContextPathMethod = getHttpServletRequestMethod("getContextPath");
        getServletPathMethod = getHttpServletRequestMethod("getServletPath");
        getPathInfoMethod = getHttpServletRequestMethod("getPathInfo");
    }

    /**
     * Helper method for getting methods of the HttpServletRequest interface
     *
     * @param name name of the method
     * @return the method object
     */
    static private Method getHttpServletRequestMethod(String name) {
        Class[] paramTypes = new Class[]{};
        try {
            return HttpServletRequest.class.getMethod(name, paramTypes);
        } catch (SecurityException e) {
            throw new RuntimeException("could not get method: " +
                                       name + " from class: " + HttpServletRequest.class);
        } catch (NoSuchMethodException e) {
            throw new RuntimeException("could not get method: " +
                                       name + " from class: " + HttpServletRequest.class);
        }
    }

    /**
     * Creates a new request wrapper from a specified proxied request and
     * the mount path of the block servlet
     * @param req the request to proxy
     * @param mountPath the mount path of the servlet
     */
    public DynamicProxyRequestHandler(HttpServletRequest req, String mountPath) {
        this.wrapped = req;
        this.mountPath = mountPath;
    }

    /**
     * @see java.lang.reflect.InvocationHandler#invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
     */
    public Object invoke(Object proxy, Method method, Object[] arguments)
    throws Throwable {
        if (method.equals(getContextPathMethod)) {
            return wrapped.getContextPath() + wrapped.getServletPath();
        } else if (method.equals(getServletPathMethod)) {
            return mountPath;
        } else if (method.equals(getPathInfoMethod)) {
            String pathInfo = wrapped.getPathInfo().substring(mountPath.length());
            return pathInfo.length() == 0 ? null : pathInfo;
        } else {
            return method.invoke(wrapped, arguments);
        }
    }

}