RELEASE_2_1_13/src/deprecated/java/org/apache/cocoon/components/source/impl/AvalonToCocoonSourceInvocationHandler.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.components.source.impl;

import org.apache.avalon.framework.component.ComponentManager;
import org.apache.cocoon.ProcessingException;
import org.apache.cocoon.components.source.SourceUtil;
import org.apache.cocoon.environment.Environment;
import org.apache.cocoon.environment.ModifiableSource;
import org.apache.excalibur.source.Source;
import org.apache.excalibur.source.SourceException;
import org.apache.excalibur.source.SourceResolver;
import org.xml.sax.ContentHandler;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

/**
 * An <code>InvocationHandler</code> which acts as a proxy for excalibur
 * <code>Source</code> objects to make them compatible with the cocoon
 * <code>Source</code> interface.
 * Much of the code was taken from {@link AvalonToCocoonSource}.
 *
 * @author Stefan K&ouml;hler
 * @author <a href="mailto:cziegeler@apache.org">Carsten Ziegeler</a>
 * @version CVS $Id$
 */
public class AvalonToCocoonSourceInvocationHandler 
implements InvocationHandler {

    /** The real source */
    protected Source source;

    /** The source resolver */
    protected SourceResolver resolver;

    /** The environment */
    protected Environment environment;

    /** The manager */
    protected ComponentManager manager;
    
    /**
     * Constructor
     */
    public AvalonToCocoonSourceInvocationHandler(Source source,
                                                  SourceResolver resolver,
                                                  Environment environment,
                                                  ComponentManager manager) {
        this.source = source;
        this.resolver = resolver;
        this.environment = environment;
        this.manager = manager;
    }

    /**
     * Processes a method invocation on a proxy instance and returns the result.
     * It invokes the corresponding method of the wrapped excalibur source.
     *
     * @param proxy  the Cocoon source proxy instance that the method was invoked on
     * @param method the Method instance corresponding to the interface method
     *               invoked on the proxy instance.
     * @param args   the arguments for the interface method
     * @return       the result of the proxy method
     */
    public Object invoke( Object proxy, Method method, Object[] args ) 
    throws Throwable {
        try {
            if        (method.getName().equals("getInputStream")) { 
                return this.getInputStream(); 
            } else if (method.getName().equals("getInputSource")) { 
                return this.getInputSource(); 
            } else if (method.getName().equals("getSystemId")) {
                return this.getSystemId();
            } else if(method.getName().equals("recycle")) { 
                this.recycle(); 
                return null;  
            } else if(method.getName().equals("toSAX")) { 
                this.toSAX((ContentHandler) args[0]); 
                return null; 
            } else{
                return method.invoke(source, args);
            }
        }
        catch ( InvocationTargetException e ){
            throw e.getTargetException();
        }
    }

    /**
     * Return an <code>InputStream</code> object to read from the source.
     */
    public InputStream getInputStream()
    throws ProcessingException, IOException {
        try {
            return this.source.getInputStream();
        } catch (SourceException e) {
            throw SourceUtil.handle(e);
        }
    }

    /**
     * Return an <code>InputSource</code> object to read the XML
     * content.
     *
     * @return an <code>InputSource</code> value
     * @exception ProcessingException if an error occurs
     * @exception IOException if an error occurs
     */
    public InputSource getInputSource()
    throws ProcessingException, IOException {
        try {
            InputSource newObject = new InputSource(this.source.getInputStream());
            newObject.setSystemId(this.getSystemId());
            return newObject;
        } catch (SourceException se) {
            throw SourceUtil.handle(se);
        }
    }

    /**
     * Return the unique identifer for this source
     */
    public String getSystemId() {
        return this.source.getURI();
    }

    public void recycle() {
        this.resolver.release(this.source);
        this.source = null;
        this.environment = null;
    }

    public void refresh() {
        this.source.refresh();
    }

    /**
     * Stream content to a content handler or to an XMLConsumer.
     *
     * @throws SAXException if failed to parse source document.
     */
    public void toSAX(ContentHandler handler)
    throws SAXException {
        try {
            SourceUtil.parse(this.manager, this.source, handler);
        } catch (ProcessingException pe) {
            throw new SAXException("ProcessingException during streaming.", pe);
        } catch (IOException ioe) {
            throw new SAXException("IOException during streaming.", ioe);
        }
    }

    /**
     * Creates a dynamic proxy for an excalibur <code>Source</code> object to
     * make it behave like a cocoon <code>Source</code>.
     * @param  source the source object to be wrapped
     * @return a proxy object which implements the cocoon <code>Source</code>
     *         interface and all of the interfaces that the wrapped object
     *         implements
     * @throws SourceException in case of an error
     */
    public static org.apache.cocoon.environment.Source createProxy(Source source,
               SourceResolver resolver,
               Environment environment,
               ComponentManager manager)
    throws SourceException{
        Class[] sourceInterfaces = source.getClass().getInterfaces();
        Class[] proxyInterfaces = new Class[sourceInterfaces.length+2];

        for(int i=0; i < sourceInterfaces.length; i++) {
            proxyInterfaces[i] = sourceInterfaces[i];
        }
        
        proxyInterfaces[sourceInterfaces.length] = org.apache.cocoon.environment.Source.class;
        proxyInterfaces[sourceInterfaces.length+1]   = ModifiableSource.class;

        InvocationHandler invocationHandler = new AvalonToCocoonSourceInvocationHandler(
             source,
             resolver,
             environment,
             manager
        );

        try {
            org.apache.cocoon.environment.Source proxy;
            proxy = (org.apache.cocoon.environment.Source)Proxy.newProxyInstance(source.getClass().getClassLoader(),
                                                  proxyInterfaces, invocationHandler);
            return proxy;
        } catch(Exception e){
            throw new SourceException("Error creating proxy object", e);
        }

    }

}