java - Spring Boot @ServerEndPoint "Failed to find the root WebApplicationContext."

我在使用带有@ServerEndPoint注释类的spring时遇到问题

我正在使用Springboot 1.2.3，并且试图弄清楚如何具有端点的单个实例

@SpringBootApplication
@EnableJpaRepositories
@EnableWebSocket
public class ApplicationServer {
    public static void main(String[] args) {
        SpringApplication.run(ApplicationServer.class, args);
    }
}

Spring 配置:

@ConditionalOnWebApplication
@Configuration
public class WebSocketConfigurator {

    @Bean
    public ServerEndPoint serverEndpoint() {
        return new ServerEndPoint();
    }

    @Bean
    public ServerEndpointExporter serverEndpointExporter() {
        return new ServerEndpointExporter();
    }
}

WebSocket端点:

@ServerEndpoint(value = "/", decoders = MessageDecoder.class,
encoders = MessageEncoder.class, configurator = SpringConfigurator.class)
public class ServerEndPoint {

    private static final Logger LOG = LoggerFactory.getLogger(ServerEndPoint.class);

    public static final Set<CommunicationObserver> OBSERVERS = Sets.newConcurrentHashSet();

    @OnMessage
    public void onMessage(Session session, Message msg) {
        LOG.debug("Received msg {} from {}", msg, session.getId());
        for (CommunicationObserver o : OBSERVERS) {
            o.packetReceived(session, msg);
        }
    }

这是基于Spring WebSocket JSR-356 tutorial，但出现以下错误:

java.lang.IllegalStateException: Failed to find the root WebApplicationContext. Was ContextLoaderListener not used?
    at org.springframework.web.socket.server.standard.SpringConfigurator.getEndpointInstance(SpringConfigurator.java:68)
    at org.apache.tomcat.websocket.pojo.PojoEndpointServer.onOpen(PojoEndpointServer.java:50)
    at org.apache.tomcat.websocket.server.WsHttpUpgradeHandler.init(WsHttpUpgradeHandler.java:138)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:687)
    at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1558)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1515)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)

我已经在嵌入式模式下以及外部tomcat 8和jetty 9中进行了测试(在外部模式下，我删除了de Spring配置文件)，但是出现了相同的错误。

the only workaround i've found is to create a custom configurator.

public class SpringEndpointConfigurator extends ServerEndpointConfig.Configurator {

    private static WebApplicationContext wac;

    public SpringEndpointConfigurator() {
    }

    public SpringEndpointConfigurator(WebApplicationContext wac) {
        SpringEndpointConfigurator.wac = wac;
    }

    @Override
    public <T> T getEndpointInstance(Class<T> endpointClass) throws InstantiationException {
        T endPoint = wac.getAutowireCapableBeanFactory().getBean(endpointClass);
        return (endPoint != null) ? endPoint : wac.getAutowireCapableBeanFactory().createBean(endpointClass);
    }

使用参数化构造函数将其创建为@Bean。

我一定错过了一些可以通过SpringConfigurator类完成任务的东西，但是我不知道该怎么办。

最佳答案

SpringConfigurator使用ContextLoader获得spring上下文。 Spring Boot确实设置了ServletContext，但它从未使用ContextLoaderListener来初始化ContextLoader来保存spring上下文的静态状态。您可以尝试添加ContextLoaderListener或作为一种解决方法，可以编写自己的上下文持有者和配置器。

这是一个例子:

第一个上下文持有者和配置者:

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;

import javax.websocket.server.ServerEndpointConfig;

public class CustomSpringConfigurator extends ServerEndpointConfig.Configurator implements ApplicationContextAware {

    /**
     * Spring application context.
     */
    private static volatile BeanFactory context;

    @Override
    public <T> T getEndpointInstance(Class<T> clazz) throws InstantiationException {
        return context.getBean(clazz);
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        CustomSpringConfigurator.context = applicationContext;
    }
}

为了获得上下文，我们需要将其配置为Bean:

@ConditionalOnWebApplication
@Configuration
public class WebSocketConfigurator {

...

    @Bean
    public CustomSpringConfigurator customSpringConfigurator() {
        return new CustomSpringConfigurator(); // This is just to get context
    }
}

然后，您需要正确设置配置器:

@ServerEndpoint(value = "/", decoders = MessageDecoder.class,
encoders = MessageEncoder.class, configurator = CustomSpringConfigurator.class)
public class ServerEndPoint {
...
}

附带说明，是的，如果您删除SpringConfigurator，则您的应用程序将启动，并且您可以处理请求。但是您不能为其他bean自动接线。