改善他的代码,进行构建简易聊天web程序
大概思路:
1.@ServerEndpoint 注解下的类代表websocket连接,而且很容易就知道他是多例的,也就是每一个浏览器建立的websocket链接即一个实例,所以很容易的
我们想到对每个浏览器做标识,然后保存起来,这样经过简单处理就可以给指定用户发送信息了
2.如何给浏览器做标识,这里利用Servlet做一个简陋的登录,然后把用户名拼接在websocket的链接,然后可以通过服务端获取到query字符串
下面是代码:
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>login</title>
</head>
<body>
<form action="login" method="post">
<input type="text" name="username">
<input type="submit" value="login">
</form>
</body>
</html>
<%@ page language="java" pageEncoding="UTF-8" %>
<%
String username = (String)request.getAttribute("username");
%>
<!DOCTYPE html>
<html>
<head>
<title>Java后端WebSocket的Tomcat实现</title>
</head>
<body>
<br>
Welcome,<span id="username"><%=username%></span><br/>
<input id="text" type="text"/><br>
<button οnclick="send()">发送消息</button>
<hr/>
<button οnclick="closeWebSocket()">关闭WebSocket连接</button>
<hr/>
<div id="message"></div>
</body>
<script type="text/javascript">
var websocket = null;
var username = document.getElementById("username").textContent;
//判断当前浏览器是否支持WebSocket
if ('WebSocket' in window) {
websocket = new WebSocket("ws://localhost:8080/websocket/websocket?username="+username);
}
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();
}
//将消息显示在网页上
function setMessageInnerHTML(innerHTML) {
document.getElementById('message').innerHTML += innerHTML + '<br/>';
}
//关闭WebSocket连接
function closeWebSocket() {
websocket.close();
}
//发送消息
function send() {
var message = document.getElementById('text').value;
websocket.send(message);
}
</script>
</html>
package websocket;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet(urlPatterns = "/login")
public class loginServlet extends HttpServlet{
public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req,resp);
}
public void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String username = req.getParameter("username");
req.setAttribute("username",username);
req.getRequestDispatcher("main.jsp").forward(req,resp);
}
}
package websocket;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArraySet;
import javax.websocket.*;
import javax.websocket.server.ServerEndpoint;
/**
* @ServerEndpoint 注解是一个类层次的注解,它的功能主要是将目前的类定义成一个websocket服务器端,
* 注解的值将被用于监听用户连接的终端访问URL地址,客户端可以通过这个URL来连接到WebSocket服务器端
*/
@ServerEndpoint("/websocket")
public class WebSocketTest {
private Session session;
@OnOpen
public void onOpen(Session session){
this.session = session;
String queryStr = session.getQueryString();
UserMap.join(queryStr.split("=")[1],this);
UserMap.addOnlineCount(); //在线数加1
System.out.println("有新连接加入!当前在线人数为" + UserMap.getOnlineCount());
}
@OnClose
public void onClose(){
UserMap.subOnlineCount(); //在线数减1
System.out.println("有一连接关闭!当前在线人数为" + UserMap.getOnlineCount());
}
@OnMessage
public void onMessage(String message, Session session) {
String[] usernameAndMessage = message.split(":");
if(UserMap.exsit(usernameAndMessage[0])){
try {
UserMap.get(usernameAndMessage[0]).sendMessage(usernameAndMessage[1]);
}catch (Exception e){
e.printStackTrace();
}
}else{
System.out.println("....找不到用户");
}
}
/**
* 发生错误时调用
* @param session
* @param error
*/
@OnError
public void onError(Session session, Throwable error){
System.out.println("发生错误");
error.printStackTrace();
}
/**
* 这个方法与上面几个方法不一样。没有用注解,是根据自己需要添加的方法。
* @param message
* @throws IOException
*/
public void sendMessage(String message) throws IOException{
this.session.getBasicRemote().sendText(message);
//this.session.getAsyncRemote().sendText(message);
}
}
package websocket;
import javax.websocket.Session;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
public class UserMap {
public static Map<String,WebSocketTest> map = new HashMap<String, WebSocketTest>();
private static int onlineCount = 0;
public static boolean exsit(String key){
return map.containsKey(key);
}
public static void join(String key,WebSocketTest webSocketTest){
if(exsit(key)){
System.out.println("用户已经登录了");
}else{
map.put(key,webSocketTest);
}
}
public static WebSocketTest get(String key){
return map.get(key);
}
public static synchronized int getOnlineCount() {
return onlineCount;
}
public static synchronized void addOnlineCount() {
onlineCount++;
}
public static synchronized void subOnlineCount() {
onlineCount--;
}
}