原文链接：https://www.dubby.cn/detail.html?id=9103

1、依赖

本文使用的是Tomcat9

项目结构也是最基本的servlet的项目结构：

代码地址：github.com/dubby1994/t…

其实啥依赖都不需要，但是需要几个api，这些在Tomcat里都已经提供了，但是代码里还是需要提供一下，不然编译报错：

<dependency><groupId>javax.websocket</groupId><artifactId>javax.websocket-api</artifactId><version>1.0</version><scope>provided</scope>
</dependency>
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2、配置

ExamplesConfig.java

package cn.dubby.tomcat.study.config;
import cn.dubby.tomcat.study.ws.EchoEndpoint;
import javax.websocket.Endpoint;
import javax.websocket.server.ServerApplicationConfig;
import javax.websocket.server.ServerEndpointConfig;
import java.util.HashSet;
import java.util.Set;public class ExamplesConfig implements ServerApplicationConfig {@Overridepublic Set<ServerEndpointConfig> getEndpointConfigs(Set<Class<? extends Endpoint>> scanned) {Set<ServerEndpointConfig> result = new HashSet<>();if (scanned.contains(EchoEndpoint.class)) {result.add(ServerEndpointConfig.Builder.create(EchoEndpoint.class, "/websocket").build());}return result;}@Overridepublic Set<Class<?>> getAnnotatedEndpointClasses(Set<Class<?>> scanned) {Set<Class<?>> results = new HashSet<>();for (Class<?> clazz : scanned) {if (clazz.getPackage().getName().contains("ws")) {results.add(clazz);}}return results;}
}
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其中getEndpointConfigs是配置所有继承Endpoint的类，而getAnnotatedEndpointClasses是配置所有被@ServerEndpoint修饰的类。

3、继承Endpoint

public class EchoEndpoint extends Endpoint {private static final AtomicLong count = new AtomicLong();@Overridepublic void onOpen(Session session, EndpointConfig endpointConfig) {System.out.println("在线人数:" + count.incrementAndGet());session.addMessageHandler(new EchoMessageHandlerText(session));}@Overridepublic void onClose(Session session, CloseReason closeReason) {System.out.println("在线人数:" + count.decrementAndGet());}private static class EchoMessageHandlerText implements MessageHandler.Partial<String> {private final Session session;private EchoMessageHandlerText(Session session) {this.session = session;}@Overridepublic void onMessage(String message, boolean last) {if (session == null)return;System.out.println(session.getId() + "\t" + message);try {session.getBasicRemote().sendText(message, last);} catch (IOException e) {e.printStackTrace();}}}
}
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4、使用注解

@ServerEndpoint("/websocket2")
public class EchoEndpoint2 {private static final AtomicLong count = new AtomicLong();@OnOpenpublic void open(Session session) {System.out.println("在线人数:" + count.incrementAndGet());try {session.getBasicRemote().sendText("welcome");} catch (IOException e) {e.printStackTrace();}}@OnClosepublic void close(Session session) {System.out.println("在线人数:" + count.decrementAndGet());}@OnMessagepublic void echoTextMessage(Session session, String message) {System.out.println(session.getId() + "\t" + message);try {if (session.isOpen()) {session.getBasicRemote().sendText(message);}} catch (IOException e) {e.printStackTrace();}}@OnMessagepublic void echoBinaryMessage(Session session, ByteBuffer bb) {System.out.println(session.getId() + "\t" + bb.toString());try {if (session.isOpen()) {session.getBasicRemote().sendBinary(bb);}} catch (IOException e) {e.printStackTrace();}}@OnMessagepublic void echoPongMessage(PongMessage pm) {//pass}
}
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例子就不给了，和昨天的几乎是一样的，你可以直接用昨天的那个html来测试今天的。