使用WebSocket实现服务端向指定的客户端推送消息

写这篇博客记录一下自己在用websocket的时候遇到的坑。
需求是这样的：需要将activeMq来的数据利用websockt推送给客户端显示出来，有多个服务终端，需要将不同的消息推送到对应的服务终端上。
1.服务端代码：需要写一个WebSocketServer类，里面根据自己需要重写方法，在写一个配置类WebSocketConfig就行了。下面上代码

WebSocketServer类：

@Component
//访问服务端的url地址
@ServerEndpoint(value = "/websocket/{id}")
public class WebSocketServer {
    private static int onlineCount = 0;
    private static ConcurrentHashMap webSocketSet = new ConcurrentHashMap<>();

    //与某个客户端的连接会话，需要通过它来给客户端发送数据
    private Session session;
    private static Logger log = LogManager.getLogger(WebSocketServer.class);
    private String id = "";
    /**
     * 连接建立成功调用的方法*/
    @OnOpen
    public void onOpen(@PathParam(value = "id") String id, Session session) {
        this.session = session;
        this.id = id;//接收到发送消息的人员编号
        webSocketSet.put(id, this);     //加入set中
        addOnlineCount();           //在线数加1
        log.info("用户"+id+"加入！当前在线人数为" + getOnlineCount());
        System.out.println("连接成功");
        try {
            sendMessage("连接成功");
        } catch (IOException e) {
            log.error("websocket IO异常");
        }

    }

    /**
     * 连接关闭调用的方法
     */
    @OnClose
    public void onClose() {
        webSocketSet.remove(this);  //从set中删除
        subOnlineCount();           //在线数减1
        log.info("有一连接关闭！当前在线人数为" + getOnlineCount());
    }

    /**
     * 收到客户端消息后调用的方法
     *
     * @param message 客户端发送过来的消息*/
    @OnMessage
    public void onMessage(String message, Session session) {
        log.info("来自客户端的消息:" + message);
        //可以自己约定字符串内容，比如 内容|0 表示信息群发，内容|X 表示信息发给id为X的用户
        String sendMessage = message.split("[|]")[0];
        String sendUserId = message.split("[|]")[1];
        try {
            if(sendUserId.equals("0")) {
                sendtoAll(sendMessage);
            }else {
                sendtoUser(sendMessage, sendUserId);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    /**
     *
     * @param session
     * @param error
     */
    @OnError
    public void onError(Session session, Throwable error) {
        log.error("发生错误");
        error.printStackTrace();
    }


    public void sendMessage(String message) throws IOException {
        this.session.getBasicRemote().sendText(message);
    }

    /**
     * 发送信息给指定ID用户，如果用户不在线则返回不在线信息给自己
     * @param message
     * @param id
     * @throws IOException
     */
    public void sendtoUser(String message,String id) throws IOException {
        if (webSocketSet.get(id) != null) {
            if(!id.equals(id)) {
                webSocketSet.get(id).sendMessage("用户" + id + "发来消息：" + " 
 " + message);
            }else {
                webSocketSet.get(id).sendMessage(message);
            }
        } else {
            //如果用户不在线则返回不在线信息给自己
            sendtoUser("当前用户不在线",id);
        }
    }

    /**
     * 发送信息给所有人
     * @param message
     * @throws IOException
     */
    public void sendtoAll(String message) throws IOException {
        for (String key : webSocketSet.keySet()) {
            try {
                webSocketSet.get(key).sendMessage(message);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }


    public static synchronized int getOnlineCount() {
        return onlineCount;
    }

    public static synchronized void addOnlineCount() {
        WebSocketServer.onlineCount++;
    }

    public static synchronized void subOnlineCount() {
        WebSocketServer.onlineCount--;
    }
}

WebSocketConfig：

@Service
@Configuration
@EnableWebSocket
public class WebSocketConfig {
    @Bean
    public ServerEndpointExporter serverEndpointExporter() {
        return new ServerEndpointExporter();
    }

}

然后前端代码我是用的在线测试网页，直接百度搜索websocket在线测试就有了，输入自己的路径连接上即可，下面是我的：

然后可以自己写测试类测试一下，但是这里启动测试类的时候有个巨坑，我就是在这里被坑了很久。用测试类启动的时候会报下面一个错:`

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'serverEndpointExporter' defined in class path resource [com/wbst/common/websocket/WebSocketConfig.class]: Invocation of init method failed; nested exception is java.lang.IllegalStateException: javax.websocket.server.ServerContainer not available
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1702) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:579) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:501) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:317) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:228) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:315) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:760) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:869) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:759) ~[spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:395) ~[spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:327) ~[spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
	at org.springframework.boot.test.context.SpringBootContextLoader.loadContext(SpringBootContextLoader.java:138) [spring-boot-test-2.0.1.RELEASE.jar:2.0.1.RELEASE]
	at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContextInternal(DefaultCacheAwareContextLoaderDelegate.java:99) [spring-test-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:117) [spring-test-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.test.context.support.DefaultTestContext.getApplicationContext(DefaultTestContext.java:108) [spring-test-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.test.context.web.ServletTestExecutionListener.setUpRequestContextIfNecessary(ServletTestExecutionListener.java:190) [spring-test-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.test.context.web.ServletTestExecutionListener.prepareTestInstance(ServletTestExecutionListener.java:132) [spring-test-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:246) [spring-test-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:227) [spring-test-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:289) [spring-test-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) [junit-4.12.jar:4.12]
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:291) [spring-test-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:246) [spring-test-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97) [spring-test-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) [junit-4.12.jar:4.12]
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) [junit-4.12.jar:4.12]
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) [junit-4.12.jar:4.12]
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) [junit-4.12.jar:4.12]
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) [junit-4.12.jar:4.12]
	at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61) [spring-test-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70) [spring-test-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363) [junit-4.12.jar:4.12]
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190) [spring-test-5.0.5.RELEASE.jar:5.0.5.RELEASE]
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137) [junit-4.12.jar:4.12]
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68) [junit-rt.jar:na]
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47) [junit-rt.jar:na]
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242) [junit-rt.jar:na]
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70) [junit-rt.jar:na]

真的是一个巨坑啊，我也不知道是什么原因导致的，猜测是重复注入了Bean。这时候需要去将配置类里面的Bean注解注释起来就可以正常启动了。
ps：但是要记得测试完以后要取消这个注释。