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The private implementation classes of the Apache MyFaces Core JSF-2.3-next Implementation
There is a newer version: 4.1.0-RC2
/*
 * 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.myfaces.view;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletOutputStream;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;

/**
 * Implementation of a switching response wrapper to turn 
 * output on and off according to the JSF spec 2.0.
 * 
 * Implemented as HttpServletResponseWrapper,
 * so that the switching does not interfere with methods that
 * expect a HttpServletResponse when invoking ExternalContext.getResponse().
 */
public class HttpServletResponseSwitch extends HttpServletResponseWrapper implements ResponseSwitch
{
    private PrintWriter _switchableWriter;
    private SwitchableOutputStream _switchableOutputStream;
    private boolean _enabled = true;

    public HttpServletResponseSwitch(HttpServletResponse response)
    {
        super(response);
    }

    /**
     * Enables or disables the Response's Writer and OutputStream.
     * @param enabled
     */
    @Override
    public void setEnabled(boolean enabled)
    {
        _enabled = enabled;
    }

    /**
     * Are the Response's Writer and OutputStream currently enabled?
     * @return
     */
    @Override
    public boolean isEnabled()
    {
        return _enabled;
    }


    @Override
    public int getBufferSize()
    {
        if (isEnabled())
        {
            return super.getBufferSize();
        }
        return 0;
    }

    @Override
    public boolean isCommitted()
    {
        if (isEnabled())
        {
            return super.isCommitted();
        }
        return false;
    }

    @Override
    public void reset()
    {
        if (isEnabled())
        {
            super.reset();
        }
    }

    @Override
    public void resetBuffer()
    {
        if (isEnabled())
        {
            super.resetBuffer();
        }
    }
    
    @Override
    public void flushBuffer() throws IOException
    {
        if (isEnabled())
        {
            super.flushBuffer();
        }
    }

    @Override
    public void setResponse(ServletResponse response)
    {
        // only change the response if it is not the same object
        if (response instanceof HttpServletResponse && response != getResponse())
        {
            // our OutputStream and our Writer are not valid for the new response
            _switchableOutputStream = null;
            _switchableWriter = null;
            
            // set the new response
            super.setResponse(response);
        }
    }

    @Override
    public ServletOutputStream getOutputStream() throws IOException
    {
        if (_switchableOutputStream == null)
        {
            _switchableOutputStream = new SwitchableOutputStream(super.getOutputStream(), this);
        }
        return _switchableOutputStream;
    }

    @Override
    public PrintWriter getWriter() throws IOException
    {
        if (_switchableWriter == null)
        {
            _switchableWriter = new PrintWriter(new SwitchableWriter(super.getWriter(), this));
        }
        return _switchableWriter;
    }
    
}