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/*
 * $Id: JSONCallingConvention.java,v 1.13 2011/02/19 08:48:28 agoubard Exp $
 *
 * See the COPYRIGHT file for redistribution and use restrictions.
 */
package org.xins.server;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.json.JSONException;
import org.json.JSONObject;
import org.json.XML;

import org.xins.common.text.TextUtils;
import org.w3c.dom.Element;
import org.xins.common.xml.ElementFormatter;
import org.xml.sax.SAXException;

/**
 * The JSON calling convention.
 *
 * This version support Yahoo style JSON calls.
 * For the definition of the calling convention, look at
 * http://developer.yahoo.com/common/json.html
 *
 * This calling convention could be used for example with Google Web Toolkit.
 * For an example, look at
 * http://code.google.com/webtoolkit/documentation/examples/jsonrpc/
 *
 * @since XINS 2.0.
 * @version $Revision: 1.13 $ $Date: 2011/02/19 08:48:28 $
 * @author Anthony Goubard
 */
public class JSONCallingConvention extends CallingConvention {

   /**
    * The response encoding format.
    */
   protected static final String RESPONSE_ENCODING = "UTF-8";

   /**
    * The content type of the HTTP response.
    */
   protected static final String RESPONSE_CONTENT_TYPE = "text/javascript; charset=" + RESPONSE_ENCODING + "";

   protected String[] getSupportedMethods() {
      return new String[] { "GET", "POST" };
   }

   protected boolean matches(HttpServletRequest httpRequest) {

      String pathInfo = httpRequest.getPathInfo();
      return "json".equals(httpRequest.getParameter("output")) &&
            !TextUtils.isEmpty(pathInfo) && !pathInfo.endsWith("/");
   }

   protected FunctionRequest convertRequestImpl(HttpServletRequest httpRequest)
   throws InvalidRequestException, FunctionNotSpecifiedException {

      // Parse the parameters in the HTTP request
      Map params = gatherParams(httpRequest);

      // Remove all invalid parameters
      cleanUpParameters(params);

      // Determine function name
      String pathInfo = httpRequest.getPathInfo();
      if (TextUtils.isEmpty(pathInfo) || pathInfo.endsWith("/")) {
         throw new FunctionNotSpecifiedException();
      }
      String functionName = pathInfo.substring(pathInfo.lastIndexOf("/") + 1);

      Element dataElement = null;
      String dataString = httpRequest.getParameter("_data");
      if (!TextUtils.isEmpty(dataString)) {
         try {
            JSONObject dataSectionObject = new JSONObject(dataString);
            String dataSectionString = XML.toString(dataSectionObject);
            dataElement = ElementFormatter.parse(dataSectionString);
         } catch (JSONException jsonex) {
            throw new InvalidRequestException("Invalid JSON input data section.", jsonex);
         } catch (SAXException pex) {
            throw new InvalidRequestException("Invalid XML created from JSON object.", pex);
         }
      }

      // Store the callback if specified
      Map backpack = new HashMap();
      backpack.put("_callback", httpRequest.getParameter("callback"));

      return new FunctionRequest(functionName, params, dataElement, backpack);
   }

   protected void convertResultImpl(FunctionResult      xinsResult,
                                    HttpServletResponse httpResponse,
                                    Map backpack)
   throws IOException {

      // Send the XML output to the stream and flush
      httpResponse.setContentType(RESPONSE_CONTENT_TYPE);
      PrintWriter out = httpResponse.getWriter();
      httpResponse.setStatus(HttpServletResponse.SC_OK);

      try {
         JSONObject jsonResult = JSONRPCCallingConvention.createResultObject(xinsResult);
         if (xinsResult.getErrorCode() != null) {
            jsonResult.put("errorCode", xinsResult.getErrorCode());
         }
         String callback = (String) backpack.get("callback");
         if (!TextUtils.isEmpty(callback)) {
            out.print(callback + "(");
         }
         String jsonString = jsonResult.toString();
         out.print(jsonString);
         if (!TextUtils.isEmpty(callback)) {
            out.print(")");
         }
      } catch (JSONException jsonex) {
         throw new IOException(jsonex.getMessage());
      }

      out.close();
   }
}