Question

我想连接到Sonic Broker主题并侦听任何传入的XML消息。我做了类似下面的事情;

Application.java

@SpringBootApplication
@ComponentScan({"com.mainpack", "com.msgpack.jms"})
@EnableJms
public class Application extends SpringBootServletInitializer {

@Autowired
private JmsTopicListener jmsTopicListener;

@Override
protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
    return application.sources(Application.class);
}

@Override
public void onStartup(final ServletContext servletContext) throws ServletException {
    try {
        LogService.info(Application.class.getName(), "Starting Service...");
        super.onStartup(servletContext);
        jmsTopicListener.listenMessage();
        LogService.info(Application.class.getName(), "Service Started");
    } catch (Exception ex) {
        LogService.error(this.getClass().getName(), ex);
    }
}

public static void main(String[] args) {
    ApplicationContext context = SpringApplication.run(Application.class, args);
    LogService.info(Application.class.getName(), "Service Started...");
 }
}

JmsTopicListener.java

@Component
public class JmsTopicListener {

@Autowired
private ApplicationProperties properties;

@Autowired
private MsgListener msgListener;

public void listenMessage() {
    TopicConnectionFactory factory;
    TopicConnection connection = null;
    LogService.info(this.getClass().getName(), "Registering Broker Connection");
    try {
        factory = new progress.message.jclient.TopicConnectionFactory(properties.getBrokerURL());
        connection = factory.createTopicConnection(properties.getUserName(), properties.getPass());

        javax.jms.TopicSession subSession = (TopicSession) connection.createTopicSession(false, Session.AUTO_ACKNOWLEDGE);

        javax.jms.Topic topic = subSession.createTopic(properties.getTopicName());
        MessageConsumer subscriber = subSession.createSubscriber(topic);
        subscriber.setMessageListener(msgListener);
        connection.start();
        LogService.info(this.getClass().getName(), "Broker connected");
    } catch (Exception ex) {
        LogService.error(this.getClass().getName(), ex);
    }
 }
}

MsgListener.java

@Component
public class MsgListener implements MessageListener {

@Override
public void onMessage(Message msg) {
    if (msg instanceof XMLMessage) {
        try {
            XMLMessage m = (XMLMessage) msg;
            if (m.getText().contains("Applications")) {
                LogService.info(this.getClass().getName(), "Recieved A Applications Message");
            } else {
                LogService.info(this.getClass().getName(), "Recieved Message Does not contain Applications Tag");
            }
        } catch (Exception ex) {
            LogService.info(this.getClass().getName(), "Exception: " + ex.getMessage());
        }
    }
 }
}

当我运行此代码时，我会在jmsTopicListener.listenMessage()的第Application.java行获取nullPointer。

我在这里犯了什么错误？有没有办法可以改善这一点（我的意思是用较少的代码完成工作）？。

注意：com.mainpack包含类Application.java和ApplicationProp.java com.msgpack.jms有JmsTopicListener.java和MsgListner.java

记录器错误：

ERROR [2015-07-14 14:34:52] [com.mainpack.Application] [localhost-startStop-1] - [Exception: ]java.lang.NullPointerException
    at com.mainpack.Application.onStartup(Application.java:33)
    at org.springframework.web.SpringServletContainerInitializer.onStartup(SpringServletContainerInitializer.java:175)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5156)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:725)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:701)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:717)
    at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:945)
    at org.apache.catalina.startup.HostConfig$DeployWar.run(HostConfig.java:1768)
    at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
    at java.util.concurrent.FutureTask.run(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

Answer 1

servlet容器在应用程序生命周期的早期调用

onStartup，并在由servlet容器创建的类的实例上调用，而不是Spring Boot。这就是jmsTopicListener为null的原因。

您可以使用以onStartup注释的方法，而不是覆盖@PostConstruct。一旦它创建了Application 的实例并且注入了任何依赖项，它就会被Spring调用：

@SpringBootApplication
@ComponentScan({"com.mainpack", "com.msgpack.jms"})
@EnableJms
public class Application extends SpringBootServletInitializer {

    @Autowired
    private JmsTopicListener jmsTopicListener;

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(Application.class);
    }

    @PostConstruct
    public void listen() { 
        jmsTopicListener.listenMessage();
    }

    public static void main(String[] args) {
        ApplicationContext context = SpringApplication.run(Application.class, args);
        LogService.info(Application.class.getName(), "Service Started...");
    }
}

Answer 2

只需添加

@PostConstruct

方法，并从该方法运行代码，它将起作用。

主类中的Spring-Boot @Autowired变为null

2 个答案: