JsonpCallbackFilter.java

/* 
 Copyright 2010, Patrick Grimaud.    
 
 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 3 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 General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>. 
 
 (Patrick gave me explicit permission to use this code under the LGPL via email. -- novalis)
 
*/

package org.opentripplanner.jsonp;

import java.io.IOException;
import java.io.OutputStream;
import java.util.Map;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.opentripplanner.jsonp.GenericResponseWrapper;

public class JsonpCallbackFilter implements Filter {

    private static Log log = LogFactory.getLog(JsonpCallbackFilter.class);

    public void init(FilterConfig fConfig) throws ServletException {}

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest httpRequest = (HttpServletRequest) request;
        HttpServletResponse httpResponse = (HttpServletResponse) response;

        @SuppressWarnings("unchecked")
        Map<String, String[]> parms = httpRequest.getParameterMap();

        if(parms.containsKey("callback")) {
            if(log.isDebugEnabled())
                log.debug("Wrapping response with JSONP callback '" + parms.get("callback")[0] + "'");

            OutputStream out = httpResponse.getOutputStream();

            GenericResponseWrapper wrapper = new GenericResponseWrapper(httpResponse);

            chain.doFilter(request, wrapper);

            out.write(new String(parms.get("callback")[0] + "(").getBytes());
            out.write(wrapper.getData());
            out.write(new String(");").getBytes());

            wrapper.setContentType("text/javascript;charset=UTF-8");

            out.close();
        } else {
            chain.doFilter(request, response);
        }
    }

    public void destroy() {}
}