zkoss/zk

/* BufferedResponse.java

    Purpose:
        
    Description:
        
    History:
        Mon Jan 17 14:02:29     2005, Created by tomyeh

Copyright (C) 2005 Potix Corporation. All Rights Reserved.

{{IS_RIGHT
    This program is distributed under LGPL Version 2.1 in the hope that
    it will be useful, but WITHOUT ANY WARRANTY.
}}IS_RIGHT
*/
package org.zkoss.web.servlet;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.io.Writer;

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

import org.zkoss.web.servlet.http.HttpBufferedResponse;

/**
 * A servlet response that uses another writer or stream as
 * the output.
 *
 * @author tomyeh
 */
public class BufferedResponse extends ServletResponseWrapper {
    private Writer _writer;
    private OutputStream _stream;

    private PrintWriter _pwt;
    private ServletOutputStream _sos;

    /** Returns a buffered response with a writer, if writer is not null;
     * or the original response if writer is null.
     * If response is HttpServletResponse, {@link HttpBufferedResponse#getInstance}
     * is returned.
     * It is smart enough not to wrap the same writer twice.
     */
    public static final ServletResponse getInstance(ServletResponse response, Writer writer) {
        if (response instanceof HttpServletResponse)
            return HttpBufferedResponse.getInstance((HttpServletResponse) response, writer);

        if (writer != null
                && (!(response instanceof BufferedResponse) || ((BufferedResponse) response)._writer != writer))
            return new BufferedResponse(response, writer);
        return response;
    }

    /** Returns a buffered response with a output stream, if stream is not null;
     * or the original response if stream is null.
     * If response is HttpServletResponse, {@link HttpBufferedResponse#getInstance}
     * is returned.
     * It is smart enough not to wrap the same stream twice.
     */
    public static final ServletResponse getInstance(ServletResponse response, OutputStream stream) {
        if (response instanceof HttpServletResponse)
            return HttpBufferedResponse.getInstance((HttpServletResponse) response, stream);

        if (stream != null
                && (!(response instanceof BufferedResponse) || ((BufferedResponse) response)._stream != stream))
            return new BufferedResponse(response, stream);
        return response;
    }

    /** Constructs a buffered response with a writer. */
    private BufferedResponse(ServletResponse response, Writer writer) {
        super(response);
        if (writer == null)
            throw new NullPointerException("writer");
        _writer = writer;
    }

    /** Constructs a buffered response with an output stream. */
    private BufferedResponse(ServletResponse response, OutputStream stream) {
        super(response);
        if (stream == null)
            throw new NullPointerException("stream");
        _stream = stream;
    }

    //super//
    public PrintWriter getWriter() throws IOException {
        if (_sos != null)
            throw new IllegalStateException("getOutputStream was called");

        if (_pwt == null) {
            if (_writer != null) {
                if (_writer instanceof PrintWriter) {
                    _pwt = (PrintWriter) _writer;
                } else {
                    _pwt = new PrintWriter(_writer);
                }
            } else {
                _pwt = new PrintWriter(new OutputStreamWriter(_stream, getCharacterEncoding()));
            }
        }
        return _pwt;
    }

    public ServletOutputStream getOutputStream() throws IOException {
        if (_pwt != null)
            throw new IllegalStateException("getWriter was called");

        if (_sos == null) {
            if (_stream != null) {
                _sos = ServletOutputStreamWrapper.getInstance(_stream);
            } else {
                throw new UnsupportedOperationException("ServletOutputStream cannot wrap PrintWriter");
            }
        }
        return _sos;
    }

    public void flushBuffer() throws IOException {
        if (_writer != null)
            _writer.flush();
        else
            _stream.flush();
    }

    /** Useful only if StringWriter or ByteArrayOutputStream is used
     * to construct this object.
     */
    public void resetBuffer() {
        if (_writer instanceof StringWriter) {
            ((StringWriter) _writer).getBuffer().setLength(0);
        } else if (_stream instanceof ByteArrayOutputStream) {
            ((ByteArrayOutputStream) _stream).reset();
        }
    }
}