java 实现websocket的两种方式

简单说明

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

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。

方法二：spring整合

此方式基于spring mvc框架，相关配置可以看我的相关博客文章

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">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

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