1.WebSocket定义
- websocket就是基于http协议的socket。
普通的http是一问一答形式，请求后才有响应，服务端(浏览器)不能主动推送消息。 - HTTP1.0生命周期是通过Request界定，一个Request一个Response，则请求就结束了；
- HTTP1.1中有一个keep-alive，在一个HTTP连接中，可以发送多个Request，接收多个Response，Response和Request对应的，且Response是被动的，不能主动发起
1.1 技术应用[在线客服]
2.WebSocket的前端Api
创建连接
var socket = new WebSocket("ws://[ip]:[port]");
生命周期
onopen()
onmessage()
onerror()
onclose()
主动方法
socket.send()
socket.close()
3.WebSocket的后端实现
3.1 创建Server
@ServerEndpoint()
3.2 Session相关 [区别于Servlet的Session]
操作server主要操作的就是server对应的session对象 [前后端联系的关键]
server.session.getBasicRemote().sendText();
4.官方示例
tomcat官方的示例
++推荐作为api参考着写自己的需求。++
页面
Java类
前端
<?xml version="1.0" encoding="UTF-8"?>
<!--
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements. See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
<title>Apache Tomcat WebSocket Examples: Chat</title>
<style type="text/css"><![CDATA[
input#chat {
410px
}
#console-container {
400px;
}
#console {
border: 1px solid #CCCCCC;
border-right-color: #999999;
border-bottom-color: #999999;
height: 170px;
overflow-y: scroll;
padding: 5px;
100%;
}
#console p {
padding: 0;
margin: 0;
}
]]></style>
<script type="application/javascript"><![CDATA[
"use strict";
var Chat = {};
Chat.socket = null;
Chat.connect = (function(host) {
if ('WebSocket' in window) {
Chat.socket = new WebSocket(host);
} else if ('MozWebSocket' in window) {
Chat.socket = new MozWebSocket(host);
} else {
Console.log('Error: WebSocket is not supported by this browser.');
return;
}
Chat.socket.onopen = function () {
Console.log('Info: WebSocket connection opened.');
document.getElementById('chat').onkeydown = function(event) {
if (event.keyCode == 13) {
Chat.sendMessage();
}
};
};
Chat.socket.onclose = function () {
document.getElementById('chat').onkeydown = null;
Console.log('Info: WebSocket closed.');
};
Chat.socket.onmessage = function (message) {
Console.log(message.data);
};
});
Chat.initialize = function() {
if (window.location.protocol == 'http:') {
Chat.connect('ws://' + window.location.host + '/examples/websocket/chat');
} else {
Chat.connect('wss://' + window.location.host + '/examples/websocket/chat');
}
};
Chat.sendMessage = (function() {
var message = document.getElementById('chat').value;
if (message != '') {
Chat.socket.send(message);
document.getElementById('chat').value = '';
}
});
var Console = {};
Console.log = (function(message) {
var console = document.getElementById('console');
var p = document.createElement('p');
p.style.wordWrap = 'break-word';
p.innerHTML = message;
console.appendChild(p);
while (console.childNodes.length > 25) {
console.removeChild(console.firstChild);
}
console.scrollTop = console.scrollHeight;
});
Chat.initialize();
document.addEventListener("DOMContentLoaded", function() {
// Remove elements with "noscript" class - <noscript> is not allowed in XHTML
var noscripts = document.getElementsByClassName("noscript");
for (var i = 0; i < noscripts.length; i++) {
noscripts[i].parentNode.removeChild(noscripts[i]);
}
}, false);
]]></script>
</head>
<body>
<div class="noscript"><h2 style="color: #ff0000">Seems your browser doesn't support Javascript! Websockets rely on Javascript being enabled. Please enable
Javascript and reload this page!</h2></div>
<div>
<p>
<input type="text" placeholder="type and press enter to chat" id="chat" />
</p>
<div id="console-container">
<div id="console"/>
</div>
</div>
</body>
</html>
后端
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package websocket.chat;
import java.io.IOException;
import java.util.Set;
import java.util.concurrent.CopyOnWriteArraySet;
import java.util.concurrent.atomic.AtomicInteger;
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;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import util.HTMLFilter;
@ServerEndpoint(value = "/websocket/chat")
public class ChatAnnotation {
private static final Log log = LogFactory.getLog(ChatAnnotation.class);
private static final String GUEST_PREFIX = "Guest";
private static final AtomicInteger connectionIds = new AtomicInteger(0);
private static final Set<ChatAnnotation> connections =
new CopyOnWriteArraySet<>();
private final String nickname;
private Session session;
public ChatAnnotation() {
nickname = GUEST_PREFIX + connectionIds.getAndIncrement();
}
@OnOpen
public void start(Session session) {
this.session = session;
connections.add(this);
String message = String.format("* %s %s", nickname, "has joined.");
broadcast(message);
}
@OnClose
public void end() {
connections.remove(this);
String message = String.format("* %s %s",
nickname, "has disconnected.");
broadcast(message);
}
@OnMessage
public void incoming(String message) {
// Never trust the client
String filteredMessage = String.format("%s: %s",
nickname, HTMLFilter.filter(message.toString()));
broadcast(filteredMessage);
}
@OnError
public void onError(Throwable t) throws Throwable {
log.error("Chat Error: " + t.toString(), t);
}
private static void broadcast(String msg) {
for (ChatAnnotation client : connections) {
try {
synchronized (client) {
client.session.getBasicRemote().sendText(msg);
}
} catch (IOException e) {
log.debug("Chat Error: Failed to send message to client", e);
connections.remove(client);
try {
client.session.close();
} catch (IOException e1) {
// Ignore
}
String message = String.format("* %s %s",
client.nickname, "has been disconnected.");
broadcast(message);
}
}
}
}