WebSocket实现Android消息推送

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>

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