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

总结

以上所述是小编给大家介绍的java 实现websocket的两种方式实例详解网站的支持！

来源：https://blog.csdn.net/sinat_23324343/article/details/81237973