使用Glassfish和Jetty的Java WebSockets教程
时间：2020-02-23 14:37:17 来源:igfitidea点击:
在本教程中，将介绍如何在GlassFish4上运行一个简单的聊天应用程序。我将使用两个API来实现这一点：Jetty和JSON API。
我们将首先从基于web的客户端开始。请看下面的图片。它有一个输入用户名的字段，一个可以输入聊天信息的字段，还有一个保存到目前为止对话的文本区域。
Web客户端和Javascript
我们可以利用
WebSocket
在JavaScript中创建客户端和服务器之间的全双工连接。JavaScript
Websocket
有3种方法
onopen–当客户机和服务器创建连接时调用此函数
onmessage–当服务器向客户机发送消息时执行此方法
onclose–当客户端和服务器之间的连接被破坏时调用此方法
用户点击send按钮后，用户名和消息本身被转换成JSON格式并发送到服务器。
我们可以在下面找到客户端的完整代码：
<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:h="http://java.sun.com/jsf/html">
<h:head>
<title>WebSockets Chat</title>
<meta name="author" content="theitroad.local"
<script type="text/javascript" charset="utf-8" src="js/jquery-1.3.2.js"></script>
<link type="text/css" rel="stylesheet" href="css/style.css"
<script type="text/javascript">
var ws;
$(document).ready(
function() {
ws = new WebSocket("ws://localhost:8080/chat");
ws.onopen = function(event) {
}
ws.onmessage = function(event) {
var $textarea = $('#messages');
var json = JSON.parse(event.data);
$textarea.val($textarea.val() + json.username + ": " + json.message + "\n");
$textarea.animate({
scrollTop : $textarea.height()
}, 1000);
}
ws.onclose = function(event) {
}
});
function sendMessage() {
var message = {
"username": $('#username').val(),
"message": $('#message').val()
}
ws.send(JSON.stringify(message));
$('#message').val('');
}
</script>
</h:head>
<h:body>
<div id="body">
<div id="menu">
User: <input id="username" value="anonymous"
<div style="clear: both"></div>
</div>
<div id="chatbox">
<textarea id="messages" rows="16" cols="50" readonly="readonly"></textarea>
</div>
<form name="message" action="">
<input name="usermsg" type="text" id="message" size="63" <input
type="button" name="submitmsg" value="Send..."
onclick="sendMessage();"
</form>
</div>
</h:body>
</html>
实现Websocket服务器
我将使用glassfish4.1来部署WebSocket服务器。我们将使用jetty9.x作为Websocket服务器，Glassfish已经在Jetty中内置了。我们将使用的另一个API是JSON API，它也是glassfish4的一部分。查看下面的pomen依赖项
<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>net.theitroad</groupId> <artifactId>ChatServer</artifactId> <version>0.0.1</version> <packaging>war</packaging> <name>ChatServer</name> <url>http://theitroad.local</url> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <dependencies> <dependency> <groupId>javax</groupId> <artifactId>javaee-api</artifactId> <version>6.0</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.eclipse.jetty</groupId> <artifactId>jetty-server</artifactId> <version>9.2.7.v20140116</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.eclipse.jetty.websocket</groupId> <artifactId>javax-websocket-server-impl</artifactId> <version>9.2.7.v20140116</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.eclipse.jetty</groupId> <artifactId>jetty-annotations</artifactId> <version>9.2.7.v20140116</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.eclipse.jetty</groupId> <artifactId>jetty-webapp</artifactId> <version>9.2.7.v20140116</version> <scope>provided</scope> </dependency> <dependency> <groupId>javax.json</groupId> <artifactId>javax.json-api</artifactId> <version>1.0</version> <scope>provided</scope> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>3.1</version> <inherited>true</inherited> <configuration> <source>1.6</source> <target>1.6</target> </configuration> </plugin> <plugin> <artifactId>maven-war-plugin</artifactId> <version>2.3</version> <configuration> <webXml>src/main/webapp/WEB-INF/web.xml</webXml> </configuration> </plugin> </plugins> </build> </project>
ChatMessage对象保存用户名，消息字符串提供一个解码器和编码器来将结构转换为JSON格式。
package net.theitroad.chatserver.pojos;
import java.io.StringReader;
import java.util.Collections;
import javax.json.Json;
import javax.json.JsonObject;
import javax.json.JsonReader;
import javax.json.JsonReaderFactory;
import javax.websocket.DecodeException;
import javax.websocket.Decoder;
import javax.websocket.EncodeException;
import javax.websocket.Encoder;
import javax.websocket.EndpointConfig;
public class ChatMessage {
public static class MessageEncoder implements Encoder.Text<ChatMessage> {
@Override
public void init(EndpointConfig config) {
}
@Override
public String encode(ChatMessage message) throws EncodeException {
return Json.createObjectBuilder()
.add("username", message.getUsername())
.add("message", message.getMessage()).build().toString();
}
@Override
public void destroy() {
}
}
public static class MessageDecoder implements Decoder.Text<ChatMessage> {
private JsonReaderFactory factory = Json
.createReaderFactory(Collections.<String, Object> emptyMap());
@Override
public void init(EndpointConfig config) {
}
@Override
public ChatMessage decode(String str) throws DecodeException {
ChatMessage message = new ChatMessage();
JsonReader reader = factory.createReader(new StringReader(str));
JsonObject json = reader.readObject();
message.setUsername(json.getString("username"));
message.setMessage(json.getString("message"));
return message;
}
@Override
public boolean willDecode(String str) {
return true;
}
@Override
public void destroy() {
}
}
private String username;
private String message;
public ChatMessage() {
}
public ChatMessage(String username, String message) {
super();
this.username = username;
this.message = message;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
}
最后，我们需要Websocket服务器端点。
package net.theitroad.chatserver.sockets;
import java.io.IOException;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import javax.websocket.EncodeException;
import javax.websocket.OnClose;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;
import net.theitroad.chatserver.pojos.ChatMessage;
import net.theitroad.chatserver.pojos.ChatMessage.MessageDecoder;
import net.theitroad.chatserver.pojos.ChatMessage.MessageEncoder;
@ServerEndpoint(value = "/chat", encoders = { MessageEncoder.class }, decoders = { MessageDecoder.class })
public class ChatServerEndpoint {
private static final Set<Session> sessions = Collections
.synchronizedSet(new HashSet<Session>());
@OnOpen
public void onOpen(Session session) {
sessions.add(session);
}
@OnClose
public void onClose(Session session) {
sessions.remove(session);
}
@OnMessage
public void onMessage(ChatMessage message, Session client)
throws IOException, EncodeException {
for (Session session : sessions) {
session.getBasicRemote().sendObject(message);
}
}
}
