impl/src/main/java/org/apache/myfaces/view/ServletViewResponseWrapper.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.myfaces.view;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
import java.io.ByteArrayOutputStream;
import java.io.CharArrayWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.Writer;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import javax.servlet.WriteListener;

/**
 * @author Bruno Aranda (latest modification by $Author$)
 * @version $Revision$ $Date$
 */
public class ServletViewResponseWrapper extends HttpServletResponseWrapper implements ViewResponseWrapper
{
    private PrintWriter _writer;
    private CharArrayWriter _charArrayWriter;
    private int _status = HttpServletResponse.SC_OK;
    private WrappedServletOutputStream _byteArrayWriter;

    public ServletViewResponseWrapper(HttpServletResponse httpServletResponse)
    {
        super(httpServletResponse);
    }

    @Override
    public void sendError(int status) throws IOException
    {
        super.sendError(status);
        _status = status;
    }

    @Override
    public void sendError(int status, String errorMessage) throws IOException
    {
        super.sendError(status, errorMessage);
        _status = status;
    }

    @Override
    public void setStatus(int status)
    {
        super.setStatus(status);
        _status = status;
    }

    @Override
    public void setStatus(int status, String errorMessage)
    {
        super.setStatus(status, errorMessage);
        _status = status;
    }

    @Override
    public int getStatus()
    {
        return _status;
    }

    public void flushToWrappedResponse() throws IOException
    {
        if (_charArrayWriter != null)
        {
            _charArrayWriter.writeTo(getResponse().getWriter());
            _charArrayWriter.reset();
            _writer.flush();
        }
        else if (_byteArrayWriter != null)
        {
            // MYFACES-1955 cannot call getWriter() after getOutputStream()
            // _byteArrayWriter is not null only if getOutputStream() was called
            // before. This method is called from f:view to flush data before tag
            // start, or if an error page is flushed after dispatch.
            // A resource inside /faces/* (see MYFACES-1815) is handled on flushToWriter.
            // If response.getOuputStream() was called before, an IllegalStateException
            // is raised on response.getWriter(), so we should try through stream.
            try
            {
                _byteArrayWriter.writeTo(getResponse().getWriter(), getResponse().getCharacterEncoding());
            }
            catch (IllegalStateException e)
            {
                getResponse().getOutputStream().write(_byteArrayWriter.toByteArray());
            }
            _byteArrayWriter.reset();
            _byteArrayWriter.flush();
        }
    }

    @Override
    public void flushToWriter(Writer writer,String encoding) throws IOException
    {
        if (_charArrayWriter != null)
        {
            _charArrayWriter.writeTo(writer);
            _charArrayWriter.reset();
            _writer.flush();
        }
        else if (_byteArrayWriter != null)
        {
            _byteArrayWriter.writeTo(writer,encoding);
            _byteArrayWriter.reset();
            _byteArrayWriter.flush();
        }
        writer.flush();
    }

    @Override
    public ServletOutputStream getOutputStream() throws IOException
    {
        if (_charArrayWriter != null)
        {
            throw new IllegalStateException();
        }
        if (_byteArrayWriter == null)
        {
            _byteArrayWriter = new WrappedServletOutputStream();
        }
        return _byteArrayWriter;
    }

    @Override
    public PrintWriter getWriter() throws IOException
    {
        if (_byteArrayWriter != null)
        {
            throw new IllegalStateException();
        }
        if (_writer == null)
        {
            _charArrayWriter = new CharArrayWriter(4096);
            _writer = new PrintWriter(_charArrayWriter);
        }
        return _writer;
    }

    @Override
    public void reset()
    {
        if (_charArrayWriter != null)
        {
            _charArrayWriter.reset();
        }
    }

    @Override
    public String toString()
    {
        if (_charArrayWriter != null)
        {
            return _charArrayWriter.toString();
        }
        return null;
    }

    static class WrappedServletOutputStream extends ServletOutputStream
    {
        private WrappedByteArrayOutputStream baos;

        public WrappedServletOutputStream()
        {
            baos = new WrappedByteArrayOutputStream(1024);
        }

        @Override
        public void write(int i) throws IOException
        {
            baos.write(i);
        }

        public byte[] toByteArray()
        {
            return baos.toByteArray();
        }
        
        /**
         * Write the data of this stream to the writer, using
         * the charset encoding supplied or if null the default charset.
         * 
         * @param out
         * @param encoding
         * @throws IOException
         */
        private void writeTo(Writer out, String encoding) throws IOException
        {
            //Get the charset based on the encoding or return the default if encoding == null
            Charset charset = encoding == null
                    ? Charset.defaultCharset()
                    : Charset.forName(encoding);

            CharsetDecoder decoder = charset.newDecoder();
            CharBuffer decodedBuffer = decoder.decode(
                    ByteBuffer.wrap(baos.getInnerArray(), 0, baos.getInnerCount()));
            if (decodedBuffer.hasArray())
            {
                out.write(decodedBuffer.array());
            }
        }

        public void reset()
        {
            baos.reset();
        }

        @Override
        public boolean isReady()
        {
            return true;
        }

        @Override
        public void setWriteListener(WriteListener wl)
        {
            
        }
        
        /**
         * This Wrapper is used to provide additional methods to 
         * get the buf and count variables, to use it to decode
         * in WrappedServletOutputStream.writeTo and avoid buffer
         * duplication.
         */
        static class WrappedByteArrayOutputStream extends ByteArrayOutputStream
        {
            public WrappedByteArrayOutputStream()
            {
                super();
            }
            
            public WrappedByteArrayOutputStream(int size)
            {
                super(size);                
            }
            
            private byte[] getInnerArray()
            {
                return buf; 
            }
            
            private int getInnerCount()
            {
                return count;
            }
        }

    }
}