ch.entwine.weblounge.kernel.publisher.JSONResponseWrapper.java Source code

Introduction

Here is the source code for ch.entwine.weblounge.kernel.publisher.JSONResponseWrapper.java

Source

/*
 *  Weblounge: Web Content Management System
 *  Copyright (c) 2003 - 2011 The Weblounge Team
 *  http://entwinemedia.com/weblounge
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public License
 *  as published by the Free Software Foundation; either version 2
 *  of the License, or (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program; if not, write to the Free Software Foundation
 *  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */

package ch.entwine.weblounge.kernel.publisher;

import org.apache.commons.lang.StringUtils;
import org.json.JSONException;
import org.json.JSONObject;
import org.json.XML;

import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.Writer;

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

/**
 * Servlet response wrapper that will convert the response from <code>xml</code>
 * to <code>json</code>.
 */
public class JSONResponseWrapper extends HttpServletResponseWrapper {

    /** Byte array used to buffer the servlet output */
    private ByteArrayServletOutputStream servletOutputStream = null;

    /** Print writer */
    private PrintWriter printWriter = null;

    /** The character encoding */
    protected String encoding = null;

    /**
     * Creates a new response wrapper that will convert the response from
     * <code>xml</code> to <code>json</code>.
     * 
     * @param response
     *          the response to wrap
     */
    public JSONResponseWrapper(HttpServletResponse response) {
        super(response);
        response.setContentType("application/json");
    }

    /**
     * {@inheritDoc}
     * 
     * @see javax.servlet.ServletResponseWrapper#setContentLength(int)
     */
    @Override
    public void setContentLength(int len) {
        // ignore
    }

    /**
     * {@inheritDoc}
     * 
     * @see javax.servlet.ServletResponseWrapper#setContentType(java.lang.String)
     */
    @Override
    public void setContentType(String type) {
        // ignore
    }

    /**
     * {@inheritDoc}
     * 
     * @see javax.servlet.ServletResponseWrapper#getOutputStream()
     */
    @Override
    public ServletOutputStream getOutputStream() throws IOException {
        if (printWriter != null)
            throw new IllegalStateException("Servlet already accessed print writer");

        if (servletOutputStream == null) {
            servletOutputStream = new ByteArrayServletOutputStream();
        }
        return servletOutputStream;
    }

    /**
     * {@inheritDoc}
     * 
     * @see javax.servlet.ServletResponseWrapper#getWriter()
     */
    @Override
    public PrintWriter getWriter() throws IOException {
        if (printWriter == null && servletOutputStream != null)
            throw new IllegalStateException("Servlet already accessed output stream");

        if (printWriter == null) {
            servletOutputStream = new ByteArrayServletOutputStream();
            encoding = getResponse().getCharacterEncoding();
            Writer writer = new OutputStreamWriter(servletOutputStream, encoding);
            printWriter = new PrintWriter(writer);
        }
        return printWriter;
    }

    /**
     * Finishes the response by converting the current content of the buffered
     * servlet output stream to json and writing it to the original response.
     * 
     * @throws IOException
     *           if writing the response fails
     * @throws JSONException
     *           if the conversion to json failed
     */
    public void finishResponse() throws IOException, JSONException {
        if (servletOutputStream != null) {
            if (printWriter != null) {
                printWriter.flush();
            }

            // Make sure there is a default encoding
            if (encoding == null)
                encoding = "utf-8";

            // Convert the current xml content to json
            Writer responseWriter = getResponse().getWriter();
            String xml = null;
            if (StringUtils.isNotBlank(encoding)) {
                xml = new String(servletOutputStream.getBytes(), encoding);
            } else {
                xml = new String(servletOutputStream.getBytes(), "utf-8");
            }
            JSONObject json = XML.toJSONObject(xml);

            // Write json back to the response
            responseWriter.write(json.toString());
        }
    }

    /**
     * {@inheritDoc}
     * 
     * @see javax.servlet.ServletResponseWrapper#resetBuffer()
     */
    @Override
    public void resetBuffer() {
        servletOutputStream = null;
        printWriter = null;
        super.resetBuffer();
    }

    /**
     * {@inheritDoc}
     * 
     * @see javax.servlet.ServletResponseWrapper#reset()
     */
    @Override
    public void reset() {
        servletOutputStream = null;
        printWriter = null;
        super.reset();
    }

}