Android 基於Netty的訊息推送方案之字串的接收和發送（三）

Android 基於Netty的訊息推送方案之字串的接收和發送（三）

在上一篇文章中《Android 基於Netty的訊息推送方案之概念和工作原理(二)》 ，我們介紹過一些關於Netty的概念和工作原理的內容，今天我們先來介紹一個叫做ChannelBuffer的東東。

ChannelBuffer

Netty中的訊息傳遞，都必須以位元組的形式，以ChannelBuffer為載體傳遞。簡單的說，就是你想直接寫個字串過去，對不起，拋異常。雖然，Netty定義的writer的介面參數是Object的，這可能也是會給新上手的朋友容易造成誤會的地方。Netty源碼中，是這樣判斷的。

<喎?http://www.bkjia.com/kf/ware/vc/" target="_blank" class="keylink">vcD4KPHByZSBjbGFzcz0="brush:java;">SendBuffer acquire(Object message) { if (message instanceof ChannelBuffer) { return acquire((ChannelBuffer) message); } else if (message instanceof FileRegion) { return acquire((FileRegion) message); } throw new IllegalArgumentException( "unsupported message type: " + message.getClass()); }接下來我們寫一個Demo來學習它。

服務端代碼如下

public class MessageServer {public static void main(String args[]){//服務啟動器ServerBootstrap bootstrap = new ServerBootstrap(new NioServerSocketChannelFactory(Executors.newCachedThreadPool(),Executors.newCachedThreadPool()));//設定一個處理用戶端訊息和各種訊息事件的類(Handler)bootstrap.setPipelineFactory(new ChannelPipelineFactory(){@Overridepublic ChannelPipeline getPipeline() throws Exception {return Channels.pipeline(new BusinessHandler());}});//開放8000連接埠供用戶端串連bootstrap.bind(new InetSocketAddress(8000));}private static class BusinessHandler extends SimpleChannelHandler{// 服務端收到用戶端發送過來的訊息時，觸發此方法@Override        public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {        ChannelBuffer buffer = (ChannelBuffer)e.getMessage();        System.out.println("Receive:"+buffer.toString(Charset.defaultCharset()));        String msg = buffer.toString(Charset.defaultCharset()) + "has been processed!";        ChannelBuffer buffer2 = ChannelBuffers.buffer(msg.length());        buffer2.writeBytes(msg.getBytes());        e.getChannel().write(buffer2);        }}}

用戶端代碼如下

public class MessageClient {public static void main(String args[]) {ClientBootstrap bootstrap = new ClientBootstrap(new NioClientSocketChannelFactory(Executors.newCachedThreadPool(), Executors.newCachedThreadPool()));bootstrap.setPipelineFactory(new ChannelPipelineFactory() {@Overridepublic ChannelPipeline getPipeline() throws Exception {return Channels.pipeline(new MessageClientHandler());}});bootstrap.connect(new InetSocketAddress("127.0.0.1", 8000));}private static class MessageClientHandler extends SimpleChannelHandler {/** * 當綁定到服務端的時候觸發，給服務端發訊息。 */@Overridepublic void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e) {// 將字串，構造成ChannelBuffer，傳遞給服務端String msg = "Hello, I'm client.";ChannelBuffer buffer = ChannelBuffers.buffer(msg.length());buffer.writeBytes(msg.getBytes());e.getChannel().write(buffer);}}}

先啟動服務端，再啟動用戶端，可以看到服務端列印如下字串

Receive:Hello, I'm client.