java 实现websocket的两种方式实例详解

一、介绍

1.两种方式，一种使用tomcat的websocket实现，一种使用spring的websocket

2.tomcat的方式需要tomcat 7.x，JEE7的支持。

3.spring与websocket整合需要spring 4.x，并且使用了socketjs，对不支持websocket的浏览器可以模拟websocket使用

二、方式一：tomcat

使用这种方式无需别的任何配置，只需服务端一个处理类，

服务器端代码

package com.Socket; 
import java.io.IOException; 
import java.util.Map; 
import java.util.concurrent.ConcurrentHashMap; 
import javax.websocket.*; 
import javax.websocket.server.PathParam; 
import javax.websocket.server.ServerEndpoint; 
import net.sf.json.JSONObject; 
@ServerEndpoint("/websocket/{username}") 
public class WebSocket { 
 private static int onlineCount = 0; 
 private static Map<String, WebSocket> clients = new ConcurrentHashMap<String, WebSocket>(); 
 private Session session; 
 private String username; 
 @OnOpen
 public void onOpen(@PathParam("username") String username, Session session) throws IOException { 
  this.username = username; 
  this.session = session; 
  addOnlineCount(); 
  clients.put(username, this); 
  System.out.println("已连接"); 
 } 
 @OnClose
 public void onClose() throws IOException { 
  clients.remove(username); 
  subOnlineCount(); 
 } 
 @OnMessage
 public void onMessage(String message) throws IOException { 
  JSONObject jsonTo = JSONObject.fromObject(message); 
  if (!jsonTo.get("To").equals("All")){ 
   sendMessageTo("给一个人", jsonTo.get("To").toString()); 
  }else{ 
   sendMessageAll("给所有人"); 
  } 
 } 
 @OnError
 public void onError(Session session, Throwable error) { 
  error.printStackTrace(); 
 } 
 public void sendMessageTo(String message, String To) throws IOException { 
  // session.getBasicRemote().sendText(message); 
  //session.getAsyncRemote().sendText(message); 
  for (WebSocket item : clients.values()) { 
   if (item.username.equals(To) ) 
    item.session.getAsyncRemote().sendText(message); 
  } 
 } 
 public void sendMessageAll(String message) throws IOException { 
  for (WebSocket item : clients.values()) { 
   item.session.getAsyncRemote().sendText(message); 
  } 
 } 
 public static synchronized int getOnlineCount() { 
  return onlineCount; 
 } 
 public static synchronized void addOnlineCount() { 
  WebSocket.onlineCount++; 
 } 
 public static synchronized void subOnlineCount() { 
  WebSocket.onlineCount--; 
 } 
 public static synchronized Map<String, WebSocket> getClients() { 
  return clients; 
 } 
}

客户端js

var websocket = null; 
var username = localStorage.getItem("name"); 
//判断当前浏览器是否支持WebSocket 
if ('WebSocket' in window) { 
 websocket = new WebSocket("ws://" + document.location.host + "/WebChat/websocket/" + username + "/"+ _img); 
} else { 
 alert('当前浏览器 Not support websocket') 
} 
//连接发生错误的回调方法 
websocket.onerror = function() { 
 setMessageInnerHTML("WebSocket连接发生错误"); 
}; 
//连接成功建立的回调方法 
websocket.onopen = function() { 
 setMessageInnerHTML("WebSocket连接成功"); 
} 
//接收到消息的回调方法 
websocket.onmessage = function(event) { 
 setMessageInnerHTML(event.data); 
} 
//连接关闭的回调方法 
websocket.onclose = function() { 
 setMessageInnerHTML("WebSocket连接关闭"); 
} 
//监听窗口关闭事件，当窗口关闭时，主动去关闭websocket连接，防止连接还没断开就关闭窗口，server端会抛异常。 
window.onbeforeunload = function() { 
 closeWebSocket(); 
} 
//关闭WebSocket连接 
function closeWebSocket() { 
 websocket.close(); 
}

发送消息只需要使用websocket.send(“发送消息”)，就可以触发服务端的onMessage()方法，当连接时，触发服务器端onOpen()方法，此时也可以调用发送消息的方法去发送消息。关闭websocket时，触发服务器端onclose()方法，此时也可以发送消息，但是不能发送给自己，因为自己的已经关闭了连接，但是可以发送给其他人。

三、方法二：spring整合

WebSocketConfig.java

这个类是配置类，所以需要在spring mvc配置文件中加入对这个类的扫描，第一个addHandler是对正常连接的配置，第二个是如果浏览器不支持websocket，使用socketjs模拟websocket的连接。

package com.websocket; 
import org.springframework.context.annotation.Bean; 
import org.springframework.context.annotation.Configuration; 
import org.springframework.web.socket.config.annotation.EnableWebSocket; 
import org.springframework.web.socket.config.annotation.WebSocketConfigurer; 
import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistry; 
import org.springframework.web.socket.handler.TextWebSocketHandler; 
@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer { 
 @Override
 public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) { 
  registry.addHandler(chatMessageHandler(),"/webSocketServer").addInterceptors(new ChatHandshakeInterceptor()); 
  registry.addHandler(chatMessageHandler(), "/sockjs/webSocketServer").addInterceptors(new ChatHandshakeInterceptor()).withSockJS(); 
 } 
 @Bean
 public TextWebSocketHandler chatMessageHandler(){ 
  return new ChatMessageHandler(); 
 } 
}

ChatHandshakeInterceptor.java

这个类的作用就是在连接成功前和成功后增加一些额外的功能，Constants.java类是一个工具类，两个常量。

package com.websocket; 
import java.util.Map; 
import org.apache.shiro.SecurityUtils; 
import org.springframework.http.server.ServerHttpRequest; 
import org.springframework.http.server.ServerHttpResponse; 
import org.springframework.web.socket.WebSocketHandler; 
import org.springframework.web.socket.server.support.HttpSessionHandshakeInterceptor; 
public class ChatHandshakeInterceptor extends HttpSessionHandshakeInterceptor { 
 @Override
 public boolean beforeHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler, 
   Map<String, Object> attributes) throws Exception { 
  System.out.println("Before Handshake"); 
  /* 
   * if (request instanceof ServletServerHttpRequest) { 
   * ServletServerHttpRequest servletRequest = (ServletServerHttpRequest) 
   * request; HttpSession session = 
   * servletRequest.getServletRequest().getSession(false); if (session != 
   * null) { //使用userName区分WebSocketHandler，以便定向发送消息 String userName = 
   * (String) session.getAttribute(Constants.SESSION_USERNAME); if 
   * (userName==null) { userName="default-system"; } 
   * attributes.put(Constants.WEBSOCKET_USERNAME,userName); 
   * 
   * } } 
   */
  //使用userName区分WebSocketHandler，以便定向发送消息(使用shiro获取session,或是使用上面的方式) 
  String userName = (String) SecurityUtils.getSubject().getSession().getAttribute(Constants.SESSION_USERNAME); 
  if (userName == null) { 
   userName = "default-system"; 
  } 
  attributes.put(Constants.WEBSOCKET_USERNAME, userName); 
  return super.beforeHandshake(request, response, wsHandler, attributes); 
 } 
 @Override
 public void afterHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler, 
   Exception ex) { 
  System.out.println("After Handshake"); 
  super.afterHandshake(request, response, wsHandler, ex); 
 } 
}

ChatMessageHandler.java

这个类是对消息的一些处理，比如是发给一个人，还是发给所有人，并且前端连接时触发的一些动作

package com.websocket; 
import java.io.IOException; 
import java.util.ArrayList; 
import org.apache.log4j.Logger; 
import org.springframework.web.socket.CloseStatus; 
import org.springframework.web.socket.TextMessage; 
import org.springframework.web.socket.WebSocketSession; 
import org.springframework.web.socket.handler.TextWebSocketHandler; 
public class ChatMessageHandler extends TextWebSocketHandler { 
 private static final ArrayList<WebSocketSession> users;// 这个会出现性能问题，最好用Map来存储，key用userid 
 private static Logger logger = Logger.getLogger(ChatMessageHandler.class); 
 static { 
  users = new ArrayList<WebSocketSession>(); 
 } 
 /** 
  * 连接成功时候，会触发UI上onopen方法 
  */
 @Override
 public void afterConnectionEstablished(WebSocketSession session) throws Exception { 
  System.out.println("connect to the websocket success......"); 
  users.add(session); 
  // 这块会实现自己业务，比如，当用户登录后，会把离线消息推送给用户 
  // TextMessage returnMessage = new TextMessage("你将收到的离线"); 
  // session.sendMessage(returnMessage); 
 } 
 /** 
  * 在UI在用js调用websocket.send()时候，会调用该方法 
  */
 @Override
 protected void handleTextMessage(WebSocketSession session, TextMessage message) throws Exception { 
  sendMessageToUsers(message); 
  //super.handleTextMessage(session, message); 
 } 
 /** 
  * 给某个用户发送消息 
  * 
  * @param userName 
  * @param message 
  */
 public void sendMessageToUser(String userName, TextMessage message) { 
  for (WebSocketSession user : users) { 
   if (user.getAttributes().get(Constants.WEBSOCKET_USERNAME).equals(userName)) { 
    try { 
     if (user.isOpen()) { 
      user.sendMessage(message); 
     } 
    } catch (IOException e) { 
     e.printStackTrace(); 
    } 
    break; 
   } 
  } 
 } 
 /** 
  * 给所有在线用户发送消息 
  * 
  * @param message 
  */
 public void sendMessageToUsers(TextMessage message) { 
  for (WebSocketSession user : users) { 
   try { 
    if (user.isOpen()) { 
     user.sendMessage(message); 
    } 
   } catch (IOException e) { 
    e.printStackTrace(); 
   } 
  } 
 } 
 @Override
 public void handleTransportError(WebSocketSession session, Throwable exception) throws Exception { 
  if (session.isOpen()) { 
   session.close(); 
  } 
  logger.debug("websocket connection closed......"); 
  users.remove(session); 
 } 
 @Override
 public void afterConnectionClosed(WebSocketSession session, CloseStatus closeStatus) throws Exception { 
  logger.debug("websocket connection closed......"); 
  users.remove(session); 
 } 
 @Override
 public boolean supportsPartialMessages() { 
  return false; 
 } 
}

spring-mvc.xml

正常的配置文件，同时需要增加对WebSocketConfig.java类的扫描，并且增加

xmlns:websocket="http://www.springframework.org/schema/websocket"
    http://www.springframework.org/schema/websocket 
    <a target="_blank" href="http://www.springframework.org/schema/websocket/spring-websocket-4.1.xsd" rel="external nofollow" >http://www.springframework.org/schema/websocket/spring-websocket-4.1.xsd</a>

客户端

<script type="text/javascript"
  src="http://localhost:8080/Bank/js/sockjs-0.3.min.js"></script> 
 <script> 
  var websocket; 
  if ('WebSocket' in window) { 
   websocket = new WebSocket("ws://" + document.location.host + "/Bank/webSocketServer"); 
  } else if ('MozWebSocket' in window) { 
   websocket = new MozWebSocket("ws://" + document.location.host + "/Bank/webSocketServer"); 
  } else { 
   websocket = new SockJS("http://" + document.location.host + "/Bank/sockjs/webSocketServer"); 
  } 
  websocket.onopen = function(evnt) {}; 
  websocket.onmessage = function(evnt) { 
   $("#test").html("(<font color='red'>" + evnt.data + "</font>)") 
  }; 
  websocket.onerror = function(evnt) {}; 
  websocket.onclose = function(evnt) {} 
  $('#btn').on('click', function() { 
   if (websocket.readyState == websocket.OPEN) { 
    var msg = $('#id').val(); 
    //调用后台handleTextMessage方法 
    websocket.send(msg); 
   } else { 
    alert("连接失败!"); 
   } 
  }); 
 </script>

注意导入socketjs时要使用地址全称，并且连接使用的是http而不是websocket的ws