利用websocket实现android消息推送
jopen
11年前
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。
</div> 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:
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(); } }
注意,连接中使用的new Draft_17()就是使用的协议version,Tomcat 7.0的协议版本需要高于Draft_17。
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