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Java example source code file (WebSocketClientExtensionHandler.java)

This example Java source code file (WebSocketClientExtensionHandler.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

channelduplexhandler, channelpromise, exception, httprequest, httpresponse, illegalargumentexception, list, nullpointerexception, object, override, string, util, websocketclientextensionhandler, websocketclientextensionhandshaker, websocketextensiondata

The WebSocketClientExtensionHandler.java Java example source code

/*
 * Copyright 2014 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 io.netty.handler.codec.http.websocketx.extensions;

import io.netty.channel.ChannelDuplexHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelPromise;
import io.netty.handler.codec.CodecException;
import io.netty.handler.codec.http.HttpHeaderNames;
import io.netty.handler.codec.http.HttpRequest;
import io.netty.handler.codec.http.HttpResponse;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

/**
 * This handler negotiates and initializes the WebSocket Extensions.
 *
 * This implementation negotiates the extension with the server in a defined order,
 * ensures that the successfully negotiated extensions are consistent between them,
 * and initializes the channel pipeline with the extension decoder and encoder.
 *
 * Find a basic implementation for compression extensions at
 * <tt>io.netty.handler.codec.http.websocketx.extensions.compression.WebSocketClientCompressionHandler.
 */
public class WebSocketClientExtensionHandler extends ChannelDuplexHandler {

    private final List<WebSocketClientExtensionHandshaker> extensionHandshakers;

    /**
     * Constructor
     *
     * @param extensionHandshakers
     *      The extension handshaker in priority order. A handshaker could be repeated many times
     *      with fallback configuration.
     */
    public WebSocketClientExtensionHandler(WebSocketClientExtensionHandshaker... extensionHandshakers) {
        if (extensionHandshakers == null) {
            throw new NullPointerException("extensionHandshakers");
        }
        if (extensionHandshakers.length == 0) {
            throw new IllegalArgumentException("extensionHandshakers must contains at least one handshaker");
        }
        this.extensionHandshakers = Arrays.asList(extensionHandshakers);
    }

    @Override
    public void write(final ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
        if (msg instanceof HttpRequest && WebSocketExtensionUtil.isWebsocketUpgrade(((HttpRequest) msg).headers())) {
            HttpRequest request = (HttpRequest) msg;
            String headerValue = request.headers().getAsString(HttpHeaderNames.SEC_WEBSOCKET_EXTENSIONS);

            for (WebSocketClientExtensionHandshaker extentionHandshaker : extensionHandshakers) {
                WebSocketExtensionData extensionData = extentionHandshaker.newRequestData();
                headerValue = WebSocketExtensionUtil.appendExtension(headerValue,
                        extensionData.name(), extensionData.parameters());
            }

            request.headers().set(HttpHeaderNames.SEC_WEBSOCKET_EXTENSIONS, headerValue);
        }

        super.write(ctx, msg, promise);
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg)
            throws Exception {
        if (msg instanceof HttpResponse) {
            HttpResponse response = (HttpResponse) msg;

            if (WebSocketExtensionUtil.isWebsocketUpgrade(response.headers())) {
                String extensionsHeader = response.headers().getAsString(HttpHeaderNames.SEC_WEBSOCKET_EXTENSIONS);

                if (extensionsHeader != null) {
                    List<WebSocketExtensionData> extensions =
                            WebSocketExtensionUtil.extractExtensions(extensionsHeader);
                    List<WebSocketClientExtension> validExtensions =
                            new ArrayList<WebSocketClientExtension>(extensions.size());
                    int rsv = 0;

                    for (WebSocketExtensionData extensionData : extensions) {
                        Iterator<WebSocketClientExtensionHandshaker> extensionHandshakersIterator =
                                extensionHandshakers.iterator();
                        WebSocketClientExtension validExtension = null;

                        while (validExtension == null && extensionHandshakersIterator.hasNext()) {
                            WebSocketClientExtensionHandshaker extensionHandshaker =
                                    extensionHandshakersIterator.next();
                            validExtension = extensionHandshaker.handshakeExtension(extensionData);
                        }

                        if (validExtension != null && ((validExtension.rsv() & rsv) == 0)) {
                            rsv = rsv | validExtension.rsv();
                            validExtensions.add(validExtension);
                        } else {
                            throw new CodecException(
                                    "invalid WebSocket Extension handhshake for \"" + extensionsHeader + "\"");
                        }
                    }

                    for (WebSocketClientExtension validExtension : validExtensions) {
                        WebSocketExtensionDecoder decoder = validExtension.newExtensionDecoder();
                        WebSocketExtensionEncoder encoder = validExtension.newExtensionEncoder();
                        ctx.pipeline().addAfter(ctx.name(), decoder.getClass().getName(), decoder);
                        ctx.pipeline().addAfter(ctx.name(), encoder.getClass().getName(), encoder);
                    }
                }

                ctx.pipeline().remove(ctx.name());
            }
        }

        super.channelRead(ctx, msg);
    }
}

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