学习WebSocket（二） — 生命周期

时间 2019-11-10

标签学习 websocket 生命周期繁體版

原文原文链接

WebSocket的生命周期

WebSocket的端点，以事件的角度看，有四个生命周期事件：css

打开事件：此事件发生在端点上创建链接时而且在任何其余事件发生以前；
消息事件：此事件在接收WebSocket对话中另外一端发送的消息。它能够发生在WebSocket端点接收了打开事件以后而且在接收关闭事件关闭以前的任什么时候刻发生；
错误事件：此事件在WebSocket链接或端点发生错误时发生；
关闭事件：此事件在WebSocket链接或者端点发生错误时发生；

以注解来声明这的话，能够用@OnOpen、@OnMessage、@OnError和@OnClose这四个注解。html

以一个例子来体现WebSocket的生命周期：java

点击打开链接按钮，与端点进行链接，这个时候会执行@OnOpen修饰的函数。jquery

点击发送消息，向端点发送文本框中的内容，这个时候会执行@OnMessage修饰的函数。git

点击关闭客户端链接按钮，客户端终端与端点的链接，这个时候会调用@OnClick修饰的函数。github

点击关闭服务端链接：web

端点关闭链接，关闭时大多数会产生一个异常会执行由@OnError修饰的函数，具体代码以下：数据库

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>cn.net.bysoft</groupId>
	<artifactId>websocketapp</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>war</packaging>

	<dependencies>
		<!-- servlet -->
		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>javax.servlet-api</artifactId>
			<version>3.0.1</version>
		</dependency>

		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>jstl</artifactId>
			<version>1.2</version>
		</dependency>
		
		<!-- https://mvnrepository.com/artifact/javax/javaee-api -->
		<dependency>
			<groupId>javax</groupId>
			<artifactId>javaee-api</artifactId>
			<version>7.0</version>
		</dependency>
		
		<!-- https://mvnrepository.com/artifact/javax.websocket/javax.websocket-api -->
		<dependency>
			<groupId>javax.websocket</groupId>
			<artifactId>javax.websocket-api</artifactId>
			<version>1.0</version>
			<scope>provided</scope>
		</dependency>

	</dependencies>

</project>

服务端代码：apache

package cn.net.bysoft.websocketapp.lesson2;

import java.io.IOException;

import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;

@ServerEndpoint("/lifecycle")
public class LifeCycle {

	private static String START_TIME = "Start Time";
	private Session ws_session;

	@OnOpen
	public void onOpen(Session ws_session) {
		// 设置session，并记录创建链接时间
		this.ws_session = ws_session;
		ws_session.getUserProperties().put(START_TIME, System.currentTimeMillis());
		// 通知客户端链接成功
		this.sendMessage("success:opened.");
	}

	@OnMessage
	public void onMessage(String message) {
		// 若是客户端发送过来close，则关闭链接
		if ("close".equals(message)) {
			try {
				// 关闭前向客户端发送消息
				this.sendMessage("danger:server closing after " + this.getConnectionSeconds() + "s.");
				// 关闭链接
				ws_session.close();
			} catch (IOException e) {
				System.out.println("Method: onMessage, Error closeing session " + e.getMessage());
			}
			return;
		}
		// 若是消息不是close，则正常处理，处理完毕后通知客户端
		this.sendMessage("info:processed a message.");
	}

	@OnError
	public void onError(Throwable t) {
		// 发生异常时，若是链接仍是打开状态，则通知客户端错误信息
		if (ws_session.isOpen()) {
			this.sendMessage("warning:Error：" + t.getMessage());
		}
	}

	@OnClose
	public void onClose() {
		// 关闭链接时，须要作的事情在该函数内完成，例如关闭数据库链接等
		System.out.println("serivce close.");
	}

	private void sendMessage(String message) {
		try {
			// 以同步的方式向客户端发送消息
			ws_session.getBasicRemote().sendText(message);
		} catch (IOException e) {
			System.out.println("Method: sendMessage, Error closeing session " + e.getMessage());
		}
	}

	private int getConnectionSeconds() {
		long millis = System.currentTimeMillis() - ((Long) this.ws_session.getUserProperties().get(START_TIME));
		return (int) millis / 1000;
	}
}

客户端编码：bootstrap

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<!-- 新 Bootstrap 核心 CSS 文件 -->
<link rel="stylesheet"
	href="http://cdn.bootcss.com/bootstrap/3.3.0/css/bootstrap.min.css">
<!-- 可选的Bootstrap主题文件（通常不用引入） -->
<link rel="stylesheet"
	href="http://cdn.bootcss.com/bootstrap/3.3.0/css/bootstrap-theme.min.css">
<!-- jQuery文件。务必在bootstrap.min.js 以前引入 -->
<script src="http://cdn.bootcss.com/jquery/1.11.1/jquery.min.js"></script>
<!-- 最新的 Bootstrap 核心 JavaScript 文件 -->
<script src="http://cdn.bootcss.com/bootstrap/3.3.0/js/bootstrap.min.js"></script>
</head>
<body>
	<div class="container">
		<h1>WebSocket的生命周期</h1>
		<div class="row">

			<div class="col-md-12">
				<p>
					<button type="button" class="btn btn-primary"
						onclick="open_connection()">打开链接</button>
					<button type="button" class="btn btn-danger"
						onclick="closeServer()">关闭服务端链接</button>
					<button type="button" class="btn btn-danger"
						onclick="closeClient()">关闭客户端链接</button>
				</p>
			</div>
		</div>
		<div class="row">
			<form class="form-inline" role="form">
				<div class="col-md-12">
					<div class="form-group">
						<div class="input-group">
							<div class="input-group">
								<span class="input-group-addon"><span
									class="glyphicon glyphicon-send"></span></span> <input id="txtMessage"
									type="text" class="form-control" placeholder="Send Message">
							</div>
							<button type="button" class="btn btn-info"
								onclick="messageClick()">发送消息</button>
						</div>
					</div>
				</div>
			</form>
		</div>
		<div class="row">
			<div class="col-md-12">
				<p id="output">
					<br>
				</p>
			</div>
		</div>
	</div>
</body>
<script>
	var lifecycle_websocket = null;

	function init() {
		output = document.getElementById("output");
	}
	
	function dispose() {
		lifecycle_websocket.close();
		lifecycle_websocket = null;
	}

	function open_connection() {
		if (lifecycle_websocket == null) {
			lifecycle_websocket = new WebSocket(
					"ws://localhost:8080/websocketapp/lifecycle");

			lifecycle_websocket.onmessage = function(evt) {
				displayMessage(evt.data);
			}
			lifecycle_websocket.onclose = function(evt) {
				displayMessage(evt.data);
			}
			lifecycle_websocket.onerror = function(evt) {
				displayMessage(evt.data);
			}
		}
	}

	function messageClick() {
		send_message(document.getElementById("txtMessage").value);
	}

	function closeServer() {
		send_message("close");
	}

	function closeClient() {
		lifecycle_websocket.close();
		displayMessage("danger:client closed.")
	}

	function send_message(message) {
		lifecycle_websocket.send(message);
	}

	function displayMessage(message) {
		var flag = message.substring(0, message.indexOf(':'));
		var data = message.substring(message.indexOf(':') + 1);

		var pre = document.createElement("p");
		// 调用bootstrap样式
		pre.className = "text-" + flag;
		pre.innerHTML = data;
		output.appendChild(pre);
	}

	window.addEventListener("load", init, false);
	window.addEventListener("unload", dispose, false);
</script>
</html>

源码地址：https://github.com/XuePeng87/websocketapp