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