JSP Http servlet response wrapper

package com.ack.web.servlet;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletOutputStream;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpServletResponseWrapper;

/**

 * JSPHttpServletResponseWrapper is used to adapt the response of a servlet.

 * The wrappers sole responsibility is to create a JSPServletOutputStream

 * off the provided HttpServletResponse.  The JSPServletOutputStream is when

 * we can customize when is streamed back to the HTTP client.  The

 * JSPHttpServletResponseWrapper provides the infrastructural scaffolding to

 * plug into our specialising output stream.

 */

public class JSPHttpServletResponseWrapper extends HttpServletResponseWrapper {

  protected ServletOutputStream stream = null;

  protected PrintWriter writer = null;

  protected HttpServletResponse origResponse = null;

  public JSPHttpServletResponseWrapper( HttpServletResponse response ) {

    super( response );

    response.setContentType("text/plain");

    origResponse = response;

  }

  public ServletOutputStream createOutputStream()

      throws IOException {

    return ( new JSPServletOutputStream( origResponse ) );

  }

  public ServletOutputStream getOutputStream()

      throws IOException {

    if( writer != null ) {

      throw new IllegalStateException( "getWriter() has already been " +

                                       "called for this response" );

    }

    if( stream == null ) {

      stream = createOutputStream();

    }

    return stream;

  }

  public PrintWriter getWriter()

      throws IOException {

    if( writer != null ) {

      return writer;

    }

    if( stream != null ) {

      throw new IllegalStateException( "getOutputStream() has already " +

                                       "been called for this response" );

    }

    stream = createOutputStream();

    writer = new PrintWriter( stream );

    return writer;

  }

}