modules/binding-comet-runtime/src/main/java/org/apache/tuscany/sca/binding/comet/runtime/handler/CometBindingHandler.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.    
 */

package org.apache.tuscany.sca.binding.comet.runtime.handler;

import java.lang.reflect.InvocationTargetException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import javax.servlet.ServletContext;
import javax.ws.rs.FormParam;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Context;

import org.apache.tuscany.sca.binding.comet.runtime.ServletFactory;
import org.apache.tuscany.sca.interfacedef.DataType;
import org.apache.tuscany.sca.interfacedef.Operation;
import org.apache.tuscany.sca.runtime.RuntimeEndpoint;
import org.atmosphere.annotation.Broadcast;
import org.atmosphere.cpr.Broadcaster;
import org.atmosphere.cpr.DefaultBroadcaster;
import org.atmosphere.jersey.Broadcastable;
import org.atmosphere.jersey.SuspendResponse;

import com.google.gson.Gson;
import com.sun.jersey.spi.container.servlet.PerSession;

/**
 * Class serving calls coming for comet services and operations.
 */
@Path("/")
@Produces("text/html;charset=ISO-8859-1")
@PerSession
public class CometBindingHandler {

    /**
     * The object used to suspend the response and send async responses back to
     * client.
     */
    private Broadcaster broadcaster;

    /**
     * The service endpoints corresponding to each operation.
     */
    private Map<String, RuntimeEndpoint> endpoints;

    /**
     * The comet operations.
     */
    private Map<String, Operation> operations;

    /**
     * JSON converter.
     */
    private Gson gson;

    /**
     * The underlying servlet context.
     */
    @Context
    private ServletContext sc;

    /**
     * Method called at comet connect time. This suspends the response and keeps
     * the connection opened.
     * 
     * @return the suspended response
     */
    @GET
    public SuspendResponse<String> connect() {
        this.broadcaster = new DefaultBroadcaster();
        this.endpoints = (Map<String, RuntimeEndpoint>)this.sc.getAttribute(ServletFactory.ENDPOINTS_KEY);
        this.operations = (Map<String, Operation>)this.sc.getAttribute(ServletFactory.OPERATIONS_KEY);
        this.gson = new Gson();
        return new SuspendResponse.SuspendResponseBuilder<String>().broadcaster(this.broadcaster).outputComments(true)
            .build();
    }

    /**
     * Method called on service calls.
     * 
     * @param service service called
     * @param method operation called
     * @param callbackMethod the callback method from Javascript
     * @param jsonData arguments for the method sent as JSON array
     * @return object used by the Broadcaster to send response through the
     *         persisted connection
     * @throws InvocationTargetException if problems occur at service invocation
     */
    @POST
    @Path("/{service}/{method}")
    @Broadcast
    public Broadcastable callAndRespond(@PathParam("service") final String service,
                                        @PathParam("method") final String method,
                                        @FormParam("callback") final String callbackMethod,
                                        @FormParam("params") final String jsonData) throws InvocationTargetException {
        final String url = "/" + service + "/" + method;
        final RuntimeEndpoint wire = this.endpoints.get(url);
        final Operation operation = this.operations.get(url);
        final Object[] args = new Object[operation.getInputType().getLogical().size()];
        final String[] json = this.parseArray(jsonData);
        int index = 0;
        // convert each argument to the corresponding class
        for (final DataType<?> dataType : operation.getInputType().getLogical()) {
            args[index] = this.gson.fromJson(json[index], dataType.getPhysical());
            index++;
        }
        // invoke the service operation
        final Object response = wire.invoke(operation, args);
        return new Broadcastable(callbackMethod + "($.secureEvalJSON('" + this.gson.toJson(response) + "'))", "",
                                 this.broadcaster);
    }

    /**
     * Parse the JSON array containing the arguments for the method call in
     * order to avoid converting JSON to Object[]. Converting each object
     * separately to it's corresponding type avoids type mismatch problems at
     * service invocation.
     * 
     * @param jsonArray the JSON array
     * @return an array of JSON formatted objects
     */
    private String[] parseArray(final String jsonArray) {
        final List<String> objects = new ArrayList<String>();
        int bracketNum = 0;
        int parNum = 0;
        int startPos = 1;
        for (int i = 0; i < jsonArray.length(); i++) {
            switch (jsonArray.charAt(i)) {
                case '{':
                    bracketNum++;
                    break;
                case '}':
                    bracketNum--;
                    break;
                case '[':
                    parNum++;
                    break;
                case ']':
                    parNum--;
                    break;
                case ',':
                    if ((bracketNum == 0) && (parNum == 1)) {
                        objects.add(jsonArray.substring(startPos, i));
                        startPos = i + 1;
                    }
            }
        }
        // add last object
        objects.add(jsonArray.substring(startPos, jsonArray.length() - 1));
        return objects.toArray(new String[] {});
    }
}