ActiveMQ、Wildfly 和获取消息体(getBody)

Question

我是 JEE7 的新手，一直在做一些快速练习，但我遇到了一个问题。我有一个示例 Java SE 应用程序，它向 ActiveMQ 队列发送消息，我在 Wildfly 8 上部署了一个 MDB，它在消息传入时读取它们。这一切都很好，我可以使用 getText 接收消息。但是，当我使用 getBody 获取消息正文时，出现“未知错误”。谁能告诉我我做错了什么？

下面是我的代码；

/***CLIENT CODE****/
    import javax.jms.*;
    import org.apache.activemq.ActiveMQConnection;
    import org.apache.activemq.ActiveMQConnectionFactory;

    public class SimpleMessageClient {
        // URL of the JMS server. DEFAULT_BROKER_URL will just mean
        // that JMS server is on localhost
        private static String url = ActiveMQConnection.DEFAULT_BROKER_URL;

        // Name of the queue we will be sending messages to
        private static String subject = "MyQueue";

        public static void main(String[] args) throws JMSException {
            // Getting JMS connection from the server and starting it
            ConnectionFactory connectionFactory =
                new ActiveMQConnectionFactory(url);
            Connection connection = connectionFactory.createConnection();
            connection.start();

            // JMS messages are sent and received using a Session. We will
            // create here a non-transactional session object. If you want
            // to use transactions you should set the first parameter to 'true'
            Session session = connection.createSession(false,
                Session.AUTO_ACKNOWLEDGE);

            // Destination represents here our queue 'TESTQUEUE' on the
            // JMS server. You don't have to do anything special on the
            // server to create it, it will be created automatically.
            Destination destination = session.createQueue(subject);

            // MessageProducer is used for sending messages (as opposed
            // to MessageConsumer which is used for receiving them)
            MessageProducer producer = session.createProducer(destination);

            // We will send a small text message saying 'Hello' in Japanese
            TextMessage message = session.createTextMessage("Jai Hind");

            //Message someMsg=session.createMessage();
           // someMsg.

            // Here we are sending the message!
            producer.send(message);
            System.out.println("Sent message '" + message.getText() + "'");

            connection.close();
        }
    }

和消费者；

    package javaeetutorial.simplemessage.ejb;

    import java.util.logging.Level;
    import java.util.logging.Logger;
    import javax.annotation.Resource;
    import javax.ejb.ActivationConfigProperty;
    import javax.ejb.MessageDriven;
    import javax.ejb.MessageDrivenContext;
    import javax.jms.JMSException;
    import javax.jms.Message;
    import javax.jms.MessageListener;
    import javax.jms.TextMessage;


    @MessageDriven(activationConfig = {
        @ActivationConfigProperty(propertyName = "destinationType", propertyValue = "javax.jms.Queue"),
        @ActivationConfigProperty(propertyName = "destination", propertyValue = "MyQueue")
    })
    public class SimpleMessageBean implements MessageListener {

        @Resource
        private MessageDrivenContext mdc;
        static final Logger logger = Logger.getLogger("SimpleMessageBean");

        public SimpleMessageBean() {
        }

        @Override
        public void onMessage(Message inMessage) {
            try {            
if (inMessage instanceof TextMessage) {
                logger.log(Level.INFO,
                        "MESSAGE BEAN: Message received: {0}",
                        inMessage.getBody(String.class));
            } else {
                logger.log(Level.WARNING,
                        "Message of wrong type: {0}",
                        inMessage.getClass().getName());
            }
            } catch (JMSException e) {
                e.printStackTrace();
                logger.log(Level.SEVERE,
                        "SimpleMessageBean.onMessage: JMSException: {0}",
                        e.toString());
                mdc.setRollbackOnly();
            }
        }
    }

我得到的部分错误是；

16:47:48,510 ERROR [org.jboss.as.ejb3] (default-threads - 32) javax.ejb.EJBTransactionRolledbackException: Unexpected Error
16:47:48,511 ERROR [org.jboss.as.ejb3.invocation] (default-threads - 32) JBAS014134: EJB Invocation failed on component SimpleMessageBean for method public void javaeetutorial.simplemessage.ejb.SimpleMessageBean.onMessage(javax.jms.Message): javax.ejb.EJBTransactionRolledbackException: Unexpected Error
    at org.jboss.as.ejb3.tx.CMTTxInterceptor.handleInCallerTx(CMTTxInterceptor.java:157) [wildfly-ejb3-8.2.0.Final.jar:8.2.0.Final]
    at org.jboss.as.ejb3.tx.CMTTxInterceptor.invokeInCallerTx(CMTTxInterceptor.java:253) [wildfly-ejb3-8.2.0.Final.jar:8.2.0.Final]
    at org.jboss.as.ejb3.tx.CMTTxInterceptor.required(CMTTxInterceptor.java:342) [wildfly-ejb3-8.2.0.Final.jar:8.2.0.Final]

Answer 1

方法

<T> T Message.getBody(Class<T> c)

您指的是对 JMS 2.0 的补充(另请参阅:http://www.oracle.com/technetwork/articles/java/jms20-1947669.html)。

虽然 WildFly 8 完全兼容 Java EE 7 和 JMS 2.1，但当前的 ActiveMQ (5.12.0) 仍然仅限于 JMS 1.1。

由于您大概在 SimpleMessageBean 中导入了 JMS 2.1 API，因此您引用了一个根本不存在于 ActiveMQ 消息中的方法。

当您尝试对消息调用 getBody() 方法时，它无法在消息实现中解析，因此会抛出 AbstractMethodError。这会导致事务回滚，从而为您提供 EJBTransactionRolledbackException。

我看到了两个针对您的问题的即时解决方案:

1. 如果您想继续使用 ActiveMQ，请将自己限制在 JMS 1.1 API 上。您提到的 getText() 方法是 JMS 1.1 的一部分，因此可以完美运行。请在此处查看 JMS 1.1 API ( https://docs.oracle.com/javaee/6/api/javax/jms/package-summary.html)，在此处查看当前的 ActiveMQ API 文档 (http://activemq.apache.org/maven/5.12.0/apidocs/index.html)。

2. 切换到 JMS 2.x 兼容的消息代理。由于您使用的是 WildFly，我建议您看看 HornetQ ( http://hornetq.jboss.org/ )。