JsonpPollingTransport.java

/*
 * Copyright 2013 The Netty Project
 *
 * The Netty Project 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.jboss.aerogear.io.netty.handler.codec.sockjs.transport;

import static io.netty.handler.codec.http.HttpHeaders.Names.CONNECTION;
import static io.netty.handler.codec.http.HttpHeaders.Names.CONTENT_LENGTH;
import static io.netty.handler.codec.http.HttpHeaders.Names.CONTENT_TYPE;
import static io.netty.handler.codec.http.HttpResponseStatus.INTERNAL_SERVER_ERROR;
import static io.netty.handler.codec.http.HttpResponseStatus.OK;
import static io.netty.util.CharsetUtil.UTF_8;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelPromise;
import io.netty.handler.codec.http.DefaultFullHttpResponse;
import io.netty.handler.codec.http.FullHttpRequest;
import io.netty.handler.codec.http.FullHttpResponse;
import io.netty.handler.codec.http.HttpHeaders;
import io.netty.handler.codec.http.HttpRequest;
import io.netty.handler.codec.http.HttpResponseStatus;
import io.netty.handler.codec.http.HttpVersion;
import io.netty.handler.codec.http.QueryStringDecoder;
import org.jboss.aerogear.io.netty.handler.codec.sockjs.SockJsConfig;
import org.jboss.aerogear.io.netty.handler.codec.sockjs.handler.SessionHandler.Event;
import org.jboss.aerogear.io.netty.handler.codec.sockjs.protocol.Frame;
import io.netty.util.ReferenceCountUtil;

import java.util.List;

/**
 * JSON Padding (JSONP) Polling is a transport where there is no open connection between
 * the client and the server. Instead the client will issue a new request for polling from
 * and sending data to the SockJS service.
 *
 * This handler is responsible for sending data back to the client. Since JSONP is in use
 * it need to inspect the HTTP request to find the callback method which is identified as
 * a query parameter 'c'. The name of the callback method will be used to wrap the data
 * into a javascript function call which is what will returned to the client.
 *
 * @see JsonpSendTransport
 */
public class JsonpPollingTransport extends ChannelHandlerAdapter {

    private final FullHttpRequest request;
    private final SockJsConfig config;
    private String callback;

    public JsonpPollingTransport(final SockJsConfig config, final FullHttpRequest request) {
        this.request = request;
        this.config = config;
    }

    @Override
    public void channelRead(final ChannelHandlerContext ctx, final Object msg) throws Exception {
        if (msg instanceof HttpRequest) {
            final QueryStringDecoder qsd = new QueryStringDecoder(request.getUri());
            final List<String> c = qsd.parameters().get("c");
            if (c == null) {
                ReferenceCountUtil.release(msg);
                respond(ctx, request.getProtocolVersion(), INTERNAL_SERVER_ERROR, "\"callback\" parameter required");
                ctx.fireUserEventTriggered(Event.CLOSE_SESSION);
                return;
            } else {
                callback = c.get(0);
            }
        }
        ctx.fireChannelRead(msg);
    }

    @Override
    public void write(final ChannelHandlerContext ctx, final Object msg, final ChannelPromise promise)
            throws Exception {
        if (msg instanceof Frame) {
            final Frame frame = (Frame) msg;
            final ByteBuf content = wrapWithFunction(frame.content(), ctx);
            frame.release();
            final FullHttpResponse response = new DefaultFullHttpResponse(request.getProtocolVersion(), OK, content);
            response.headers().set(CONTENT_TYPE, Transports.CONTENT_TYPE_JAVASCRIPT);
            response.headers().set(CONTENT_LENGTH, content.readableBytes());
            response.headers().set(CONNECTION, HttpHeaders.Values.CLOSE);
            Transports.setNoCacheHeaders(response);
            Transports.setSessionIdCookie(response, config, request);
            ctx.writeAndFlush(response, promise);
        } else {
            ctx.write(ReferenceCountUtil.retain(msg), promise);
        }
    }

    private ByteBuf wrapWithFunction(final ByteBuf data, final ChannelHandlerContext ctx) {
        final ByteBuf content = ctx.alloc().buffer();
        Transports.escapeJson(data, content);
        final String function = callback + "(\"" + content.toString(UTF_8) + "\");\r\n";
        content.release();
        return Unpooled.copiedBuffer(function, UTF_8);
    }

    private static void respond(final ChannelHandlerContext ctx,
                                final HttpVersion httpVersion,
                                final HttpResponseStatus status,
                                final String message) throws Exception {
        final FullHttpResponse response = new DefaultFullHttpResponse(httpVersion, status);
        Transports.writeContent(response, message, Transports.CONTENT_TYPE_JAVASCRIPT);
        Transports.writeResponse(ctx, response);
    }

}