利用websocket实现安卓消息推送

来源：互联网发布：2017年公务员网络培训编辑：程序博客网时间：2024/05/16 18:12

前段时间做一个项目，需要android客户端作为管理工具与web服务器后台实时交互，想了很多方法，包括androidpn、openfire+smack、xmpp协议，要么太繁琐，要么无法满足实时性。想来还是用socket，经人提醒想到了websocket。

websocket协议是近些年随html5发展而诞生的，主要用于解决web服务器与客户端无法双向交互的问题。如今已经被W3C收入标准协议。

服务器支持：tomcat、jetty的最新版本都已支持websocket；如果不想更换现有服务器，也可用spring4.0作为替代。据说新版本的jre将收入websocket类，没具体接触。

客户端支持：目前的主流浏览器都已经实现了websocket，但由于前期协议版本变化太快，很多厂商没有跟上。android默认浏览器就不支持websocket，IE也直到IE10才支持。

网上已有通过html实现websocket client的例子，这里我们用java实现客户端连接。废话不说，上Demo：

1.服务器端

服务器用了tomcat 7.0，直接使用tomcat的websocket实现

（1）连接管理类

import java.io.IOException;import java.nio.CharBuffer;import java.util.ArrayList;import java.util.List;import org.apache.catalina.websocket.MessageInbound;import org.apache.catalina.websocket.WsOutbound; public class MessageCenter{    private static MessageCenter        instance           = new MessageCenter();     private List<MessageInbound>        socketList;     private MessageCenter()    {        this.socketList = new ArrayList<MessageInbound>();    }     public static MessageCenter getInstance()    {        return instance;    }     public void addMessageInbound(MessageInbound inbound)    {        socketList.add(inbound);    }     public void removeMessageInbound(MessageInbound inbound)    {        socketList.remove(inbound);    }     public void broadcast(CharBuffer msg) throws IOException    {        for (MessageInbound messageInbound : socketList)        {            CharBuffer buffer = CharBuffer.wrap(msg);            WsOutbound outbound = messageInbound.getWsOutbound();            outbound.writeTextMessage(CharBuffer.wrap("broadcasting:" + msg));            // outbound.writeTextMessage(buffer);            outbound.flush();        }    }}

（2）消息入口类

import java.io.IOException;import java.nio.ByteBuffer;import java.nio.CharBuffer;import java.util.Date; import org.apache.catalina.websocket.MessageInbound;import org.apache.catalina.websocket.WsOutbound; public class MyMessageInbound extends MessageInbound {     @Override    protected void onBinaryMessage(ByteBuffer arg0) throws IOException {        // TODO Auto-generated method stub             }     @Override    protected void onTextMessage(CharBuffer msg) throws IOException {        System.out.println("Received:"+msg);        MessageCenter.getInstance().broadcast(msg);             }     @Override    protected void onClose(int status) {        System.out.println("close:"+new Date());        MessageCenter.getInstance().removeMessageInbound(this);        super.onClose(status);    }     @Override    protected void onOpen(WsOutbound outbound) {        System.out.println("open :"+new Date());        super.onOpen(outbound);        MessageCenter.getInstance().addMessageInbound(this);    }}

（3）Websocket servlet

import javax.servlet.http.HttpServletRequest; import org.apache.catalina.websocket.StreamInbound;import org.apache.catalina.websocket.WebSocketServlet; public class MeWebSocketServlet extends WebSocketServlet{     private static final long serialVersionUID = -7178893327801338294L;     @Override    protected StreamInbound createWebSocketInbound(String subProtocol, HttpServletRequest request)    {        System.out.println("##########client login#########");        return new MeMessageInbound();    } }

（4）添加servlet到web.xml

  < servlet>               < servlet-name> android</ servlet-name >               < servlet-class> MyWebSocketServlet </servlet-class >        </ servlet>        < servlet-mapping>               < servlet-name> android</ servlet-name >               < url-pattern> *.do</ url-pattern >        </ servlet-mapping>

2.客户端

客户端使用java实现websocket client，

网上有人实现了Java-websocket：https://github.com/TooTallNate/Java-WebSocket 可以取得源码，用maven编译。

最新jar包下载地址：

http://download.csdn.net/detail/chifengxin/6524283

引用jar包后，实现简单消息连接：

import java.net.URI;import java.net.URISyntaxException; import org.java_websocket.client.WebSocketClient;import org.java_websocket.drafts.Draft;import org.java_websocket.drafts.Draft_10;import org.java_websocket.drafts.Draft_17;import org.java_websocket.framing.Framedata;import org.java_websocket.handshake.ServerHandshake; /** This example demonstrates how to create a websocket connection to a server. Only the most important callbacks are overloaded. */public class ExampleClient extends WebSocketClient {         public ExampleClient( URI serverUri , Draft draft ) {                super( serverUri, draft );        }         public ExampleClient( URI serverURI ) {                super( serverURI );        }         @Override        public void onOpen( ServerHandshake handshakedata ) {                System.out.println( "opened connection" );                // if you plan to refuse connection based on ip or httpfields overload: onWebsocketHandshakeReceivedAsClient        }         @Override        public void onMessage( String message ) {                System.out.println( "received: " + message );        }         @Override        public void onFragment( Framedata fragment ) {                System.out.println( "received fragment: " + new String( fragment.getPayloadData().array() ) );        }         @Override        public void onClose( int code, String reason, boolean remote ) {                // The codecodes are documented in class org.java_websocket.framing.CloseFrame                System.out.println( "Connection closed by " + ( remote ? "remote peer" : "us" ) );        }         @Override        public void onError( Exception ex ) {                ex.printStackTrace();                // if the error is fatal then onClose will be called additionally        }         public static void main( String[] args ) throws URISyntaxException {                ExampleClient c = new ExampleClient( new URI( "ws://localhost:8080/myweb/android.do" ), new Draft_17() );                c.connect();        } }

总结websocket的利弊

优点：

与socket相比，可以节省额外的端口占用，直接使用一个公网域名访问。另外协议对报文的流量消耗做了优化。

缺点：

毕竟websocket底层也是socket连接，因而当大并发用户连接时目测会消耗较多资源。

参考：

Tomcat 7.0 api http://tomcat.apache.org/tomcat-7.0-doc/api/

来自：http://blog.csdn.net/chifengxin/article/details/14521093

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