前言
曾幾何時，不知道大家有沒有在項目裏遇到過需要服務端給客戶端推送消息的需求，是否曾經苦惱過、糾結過，我們知道要想實現這樣的需求肯定離不開websocket長連接方式，那麼到底是該選原生的websocket還是更加高級的netty框架呢？在此我極力推薦netty，因爲一款好的框架一般都是在原生的基礎上進行包裝成更好、更方便、更實用的東西，很多我們需要自己考慮的問題都基本可以不用去考慮，不過此文不會去講netty有多麼的高深莫測，因爲這些概念性的東西隨處可見，而是通過實戰來達到推送消息的目的。
實戰
一、邏輯架構圖
從圖中可以看出本次實戰的基本流程是客戶端A請求服務端核心模塊，核心模塊生產一條消息到消息隊列，然後服務端消息模塊消費消息，消費完之後就將消息推送給客戶端B，流程很簡單，沒有太多技巧，唯一的巧妙之處就在消息模塊這邊的處理上，本文的重點也主要講解消息模塊這一塊，主要包括netty server、netty client、channel的存儲等等。
二、代碼
1、添加依賴
<dependency >
< groupId > io.netty</ groupId>
< artifactId > netty - all</ artifactId>
< version > 4.1 .6.Final</ version>
< / dependency>
2、NettyServer類
@Service
public class NettyServer {
public void run( int port )
{
new Thread()
{
public void run()
{
runServer( port );
}
}.start();
}
private void runServer( int port )
{
Print.info( "===============Message服務端啓動===============" );
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.group( bossGroup, workerGroup ); b.channel( NioServerSocketChannel.class );
b.childHandler( new ChannelInitializer<SocketChannel>()
{
protected void initChannel( SocketChannel ch ) throws Exception {
ChannelPipeline pipeline = ch.pipeline(); pipeline.addLast( "codec-http", new HttpServerCodec() );
pipeline.addLast( "aggregator", new HttpObjectAggregator( 65536 ) );
pipeline.addLast( "handler", new MyWebSocketServerHandler() );
}
} ); Channel ch = b.bind( port ).sync().channel(); Print.info( "Message服務器啓動成功：" + ch.toString() );
ch.closeFuture().sync();
} catch ( Exception e ) {
Print.error( "Message服務運行異常：" + e.getMessage() );
e.printStackTrace();
} finally {
bossGroup.shutdownGracefully(); workerGroup.shutdownGracefully(); Print.info( "Message服務已關閉" );
}
}
}
3、MyWebSocketServerHandler類
public class MyWebSocketServerHandler extends SimpleChannelInboundHandler<Object>{
private static final String WEBSOCKET_PATH = "";
private WebSocketServerHandshaker handshaker; @Override protected void channelRead0( ChannelHandlerContext ctx, Object msg ) throws Exception
{
if ( msg instanceof FullHttpRequest )
{
/*
* 以http請求形式接入，但是走的是websocket handleHttpRequest(ctx, (FullHttpRequest) msg); }else if (msg instanceof WebSocketFrame){
* 處理websocket客戶端的消息 handleWebSocketFrame(ctx, (WebSocketFrame) msg); } } @Override public void channelReadComplete(ChannelHandlerContext ctx) throws Exception { ctx.flush();
*/
}
private void handleHttpRequest( ChannelHandlerContext ctx, FullHttpRequest req ) throws Exception /* 要求Upgrade爲websocket，過濾掉get/Post if (!req.decoderResult().isSuccess() */
{
|| (!"websocket".equals( req.headers().get( "Upgrade" ) ) ) ) {
/* 若不是websocket方式，則創建BAD_REQUEST的req，返回給客戶端 sendHttpResponse(ctx, req, new DefaultFullHttpResponse( HttpVersion.HTTP_1_1, HttpResponseStatus.BAD_REQUEST)); return; */
} WebSocketServerHandshakerFactory wsFactory = new WebSocketServerHandshakerFactory( "ws://localhost:9502/websocket", null, false );
handshaker = wsFactory.newHandshaker( req ); if ( handshaker == null )
{
WebSocketServerHandshakerFactory.sendUnsupportedVersionResponse( ctx.channel() );
} else {
handshaker.handshake( ctx.channel(), req );
}
}
private void handleWebSocketFrame( ChannelHandlerContext ctx, WebSocketFrame frame ) /* Check for closing frame if (frame instanceof CloseWebSocketFrame) { */
{
handshaker.close( ctx.channel(), (CloseWebSocketFrame) frame.retain() ); return;
}
if ( frame instanceof PingWebSocketFrame )
{
ctx.channel().write( new PongWebSocketFrame( frame.content().retain() ) ); return;
}
if ( !(frame instanceof TextWebSocketFrame) )
{
Print.error( "數據幀類型不支持!" ); throw new UnsupportedOperationException( String.format( "%s frame types not supported", frame.getClass().getName() ) );
}
/* Send the uppercase string back. String request = ((TextWebSocketFrame) frame).text(); Print.info("Netty服務器接收到的信息: " + request); if (request.equals(Const.HEARTBEAT)){ */
ctx.channel().write( new TextWebSocketFrame( request ) ); return;
}
JSONObject jsonData = JSONObject.parseObject( request ); String eventType = jsonData.getString( "event_type" ); String apiToken = jsonData.getString( "api_token" ); if ( Const.FRONT.equals( eventType ) )
{
Print.info( "front event" ); ChannelSupervise.updateChannel( apiToken, ctx.channel() );
}else if ( Const.BEHIND.equals( eventType ) )
{
Print.info( "behind event" ); Channel chan = ChannelSupervise.findChannel( apiToken ); if ( null == chan )
{
Print.error( "目標用戶不存在" );
}else {
JSONObject jsonMsg = new JSONObject(); jsonMsg.put( "type", jsonData.get( "type" ) ); jsonMsg.put( "child_type", jsonData.get( "child_type" ) ); jsonMsg.put( "title", jsonData.get( "title" ) ); jsonMsg.put( "body", jsonData.get( "body" ) ); ChannelSupervise.sendToSimple( apiToken, new TextWebSocketFrame( jsonMsg.toString() ) ); Print.info( "向目標用戶發送成功" );
}
}else{
Print.error( "event type error" );
}
} private static void sendHttpResponse( ChannelHandlerContext ctx, FullHttpRequest req, DefaultFullHttpResponse res ) /* 返回應答給客戶端 if (res.status().code() != 200) { */
{
ByteBuf buf = Unpooled.copiedBuffer( res.status().toString(), CharsetUtil.UTF_8 ); res.content().writeBytes( buf ); buf.release();
}
ChannelFuture f = ctx.channel().writeAndFlush( res ); /* 如果是非Keep-Alive，關閉連接 if (!isKeepAlive(req) || res.status().code() != 200) { */
f.addListener( ChannelFutureListener.CLOSE ); } } @Override public void exceptionCaught( ChannelHandlerContext ctx, Throwable cause ) throws Exception
{
cause.printStackTrace(); ctx.close();
}
private static String getWebSocketLocation( FullHttpRequest req )
{
return("ws://" + req.headers().get( HOST ) + WEBSOCKET_PATH);
}
/** * 接收客戶端連接事件 */ @Override public void channelActive( ChannelHandlerContext ctx ) throws Exception
{
Print.info( "客戶端與服務端連接開啓：" + ctx.channel() ); ChannelSupervise.addChannel( null, ctx.channel() );
}
/** * 接收客戶端關閉事件 */ @Override public void channelInactive( ChannelHandlerContext ctx ) throws Exception
{
Print.info( "客戶端與服務端連接關閉：" + ctx.channel() ); ChannelSupervise.removeChannel( ctx.channel() );
}
}
4、ChannelSupervise類
public class ChannelSupervise {
private static ChannelGroup GlobalGroup = new DefaultChannelGroup( GlobalEventExecutor.INSTANCE );
private static ConcurrentMap<String, ChannelId> ChannelMap = new ConcurrentHashMap();
public static void addChannel( String apiToken, Channel channel )
{
GlobalGroup.add( channel );
if ( null != apiToken )
{
ChannelMap.put( apiToken, channel.id() );
}
}
public static void updateChannel( String apiToken, Channel channel )
{
Channel chan = GlobalGroup.find( channel.id() ); if ( null == chan )
{
addChannel( apiToken, channel );
}else {
ChannelMap.put( apiToken, channel.id() );
}
}
public static void removeChannel( Channel channel )
{
GlobalGroup.remove( channel );
Collection<ChannelId> values = ChannelMap.values(); values.remove( channel.id() );
}
public static Channel findChannel( String apiToken )
{
ChannelId chanId = ChannelMap.get( apiToken );
if ( null == chanId )
{
return(null);
}
return(GlobalGroup.find( ChannelMap.get( apiToken ) ) );
}
public static void sendToAll( TextWebSocketFrame tws )
{
GlobalGroup.writeAndFlush( tws );
}
public static void sendToSimple( String apiToken, TextWebSocketFrame tws )
{
GlobalGroup.find( ChannelMap.get( apiToken ) ).writeAndFlush( tws );
}
}
5、NettyClient類
@Servicepublic class NettyClient { private Channel channel; public void run(String strUri){ new Thread(){ public void run(){ runClient(strUri); } }.start(); private void runClient(String strUri) { EventLoopGroup group = new NioEventLoopGroup(); try { Bootstrap b = new Bootstrap(); URI uri = new URI(strUri); String protocol = uri.getScheme(); if (!"ws".equals(protocol)) { throw new IllegalArgumentException("Unsupported protocol: " + protocol); } HttpHeaders customHeaders = new DefaultHttpHeaders(); customHeaders.add("MyHeader", "MyValue"); // Connect with V13 (RFC 6455 aka HyBi-17). You can change it to V08 or V00\. // If you change it to V00, ping is not supported and remember to change // HttpResponseDecoder to WebSocketHttpResponseDecoder in the pipeline. final MyWebSocketClientHandler handler = new MyWebSocketClientHandler( WebSocketClientHandshakerFactory.newHandshaker(uri, WebSocketVersion.V13, null, false, customHeaders)); b.group(group); b.channel(NioSocketChannel.class); b.handler(new ChannelInitializer<SocketChannel>() { @Overpublic void initChannel(SocketChannel ch) throws Exception { ChannelPipeline pipeline = ch.pipeline(); pipeline.addLast("http-codec", new HttpClientCodec()); pipeline.addLast("aggregator", new HttpObjectAggregator(8192)); pipeline.addLast("ws-handler", handler); } }); Print.info("===============Message客戶端啓動==============="); channel = b.connect(uri.getHost(), uri.getPort()).sync().channel(); handler.handshakeFuture().sync(); channel.closeFuture().sync(); } catch (Exception e){ Print.error(e.getMessage()); } finally { group.shutdownGracefully(); } }@Servicepublic class NettyClient {
private Channel channel;
public void run( String strUri )
{
new Thread()
{
public void run()
{
runClient( strUri );
}
}.start(); private void runClient( String strUri )
{
EventLoopGroup group = new NioEventLoopGroup();
try {
Bootstrap b = new Bootstrap();
URI uri = new URI( strUri );
String protocol = uri.getScheme(); if ( !"ws".equals( protocol ) )
{
throw new IllegalArgumentException( "Unsupported protocol: " + protocol );
}
HttpHeaders customHeaders = new DefaultHttpHeaders();
customHeaders.add( "MyHeader", "MyValue" );
/*
* Connect with V13 (RFC 6455 aka HyBi-17). You can change it to V08 or V00.
* If you change it to V00, ping is not supported and remember to change
* HttpResponseDecoder to WebSocketHttpResponseDecoder in the pipeline.
*/
final MyWebSocketClientHandler handler =
new MyWebSocketClientHandler(
WebSocketClientHandshakerFactory.newHandshaker( uri, WebSocketVersion.V13, null, false, customHeaders ) ); b.group( group ); b.channel( NioSocketChannel.class ); b.handler( new ChannelInitializer<SocketChannel>()
{
@Overpublic void initChannel( SocketChannel ch ) throws Exception {
ChannelPipeline pipeline = ch.pipeline(); pipeline.addLast( "http-codec", new HttpClientCodec() ); pipeline.addLast( "aggregator", new HttpObjectAggregator( 8192 ) ); pipeline.addLast( "ws-handler", handler );
}
} ); Print.info( "===============Message客戶端啓動===============" ); channel = b.connect( uri.getHost(), uri.getPort() ).sync().channel(); handler.handshakeFuture().sync(); channel.closeFuture().sync();
} catch ( Exception e ) {
Print.error( e.getMessage() );
} finally {
group.shutdownGracefully();
}
}
6、MyWebSocketClientHandler類
public class MyWebSocketClientHandler extends SimpleChannelInboundHandler<Object> {
private final WebSocketClientHandshaker handshaker;
private ChannelPromise handshakeFuture;
public MyWebSocketClientHandler( WebSocketClientHandshaker handshaker )
{
this.handshaker = handshaker;
} public ChannelFuture handshakeFuture()
{
return(handshakeFuture);
}
@Override
public void handlerAdded( ChannelHandlerContext ctx ) throws Exception
{
handshakeFuture = ctx.newPromise();
}
@Override
public void channelActive( ChannelHandlerContext ctx ) throws Exception
{
handshaker.handshake( ctx.channel() );
}
@Override
public void channelInactive( ChannelHandlerContext ctx ) throws Exception
{
Print.info( "webSocket client disconnected!" );
}
@Override
public void channelRead( ChannelHandlerContext ctx, Object msg ) throws Exception
{
Channel ch = ctx.channel(); if ( !handshaker.isHandshakeComplete() )
{
handshaker.finishHandshake( ch, (FullHttpResponse) msg ); Print.info( "websocket client connected!" );
handshakeFuture.setSuccess(); return;
}
if ( msg instanceof FullHttpResponse )
{
FullHttpResponse response = (FullHttpResponse) msg; throw new Exception( "Unexpected FullHttpResponse (getStatus=" + response.getStatus() + ", content=" + response.content().toString( CharsetUtil.UTF_8 ) + ')' );
}
WebSocketFrame frame = (WebSocketFrame) msg; if ( frame instanceof TextWebSocketFrame )
{
TextWebSocketFrame textFrame = (TextWebSocketFrame) frame; Print.info( "客戶端收到消息: " + textFrame.text() );
} else if ( frame instanceof PongWebSocketFrame )
{
Print.info( "websocket client received pong" );
} else if ( frame instanceof CloseWebSocketFrame )
{
Print.info( "websocket client received closing" );
ch.close();
}
}
@Override
protected void channelRead0( ChannelHandlerContext channelHandlerContext, Object o ) throws Exception
{
}
@Override
public void exceptionCaught( ChannelHandlerContext ctx, Throwable cause ) throws Exception
{
cause.printStackTrace(); if ( !handshakeFuture.isDone() )
{
handshakeFuture.setFailure( cause );
}
ctx.close();
}
}
7、啓動類
@SpringBootApplication
@Servicepublic
class MessageApplication {
@Autowired
private NettyServer server; @Autowired
private NettyClient client; public static void main( String[] args )
{
SpringApplication.run( MessageApplication.class, args );
}
@PostConstruct
public void initMessage()
{
server.run( 9502 );
try {
Thread.sleep( 1000 );
} catch ( InterruptedException e ) {
e.printStackTrace();
} client.run( "ws://localhost:" + 9502 );
}
8、客戶端B測試頁面
<!DOCTYPE html >
< html >
< head >
< meta charset = "UTF-8" >
< title > WebSocket Chat</ title>
< / head >
< body >
< script type = "text/javascript" >
var socket;
if ( !window.WebSocket )
{
window.WebSocket = window.MozWebSocket;
}
if ( window.WebSocket )
{
socket = new WebSocket( "ws://localhost:9502" );
socket.onmessage = function( event )
{
var ta = document.getElementById( 'responseText' );
ta.value = ta.value + '\n' + event.data
};
socket.onopen = function( event )
{
var ta = document.getElementById( 'responseText' );
ta.value = "連接開啓!";
};
socket.onclose = function( event )
{
var ta = document.getElementById( 'responseText' );
ta.value = ta.value + "連接被關閉";
};
} else {
alert( "你的瀏覽器不支持 WebSocket！" );
}
function send( message )
{
if ( !window.WebSocket )
{
return;
}
if ( socket.readyState == WebSocket.OPEN )
{
socket.send( message );
} else {
alert( "連接沒有開啓." );
}
}
< / script >
< form onsubmit = "return false;" >
< h3 > WebSocket ： < / h3 >
< textarea id = "responseText" style = "width: 500px; height: 300px;" > < / textarea >
< br >
< input type = "text" name = "message" style = "width: 300px" value = "1" >
< input type = "button" value = "發送消息" onclick = "send(this.form.message.value)" >
< input type = "button" onclick = "javascript:document.getElementById('responseText').value=''" value = "清空聊天記錄" >
< / form >
< br >
< / body >
< / html>
三、測試
1、先運行啓動類，此時會先啓動netty服務器，然後啓動一個netty客戶端，然後過30s模擬客戶端A進行消息發送
2、打開測試頁面，在底下的輸入框輸入：{"event_type":"front", "api_token":"11111"}，表示客戶端B連接上netty服務器
測試結果如下：
消息模塊：
客戶端B：
四、結束語
本文只是拋磚引玉，主要啓發有類似需求的朋友知道怎麼去存儲channel，進而怎麼給指定客戶推送消息，如果想要進行大型項目的高併發、可靠穩定地使用，還需進一步地改進。