Question

我刚刚开始使用Java ee 7，这是我无法理解它是如何神奇地工作的。

我按照Antonio Goncalves的Beginning Java EE 7一书中的例子。我设法编译和部署第13章（关于JMS）的代码没有任何问题。消息按预期发送和接收，但这让我感到困惑。

源代码是使用者类，生产者类，POJO和MDB类的组合。

这是消费者：

public class OrderConsumer {

  public static void main(String[] args) throws NamingException {

    // Gets the JNDI context
    Context jndiContext = new InitialContext();

    // Looks up the administered objects
    ConnectionFactory connectionFactory = (ConnectionFactory) jndiContext.lookup("jms/javaee7/ConnectionFactory");
    Destination topic = (Destination) jndiContext.lookup("jms/javaee7/Topic");

    // Loops to receive the messages
    System.out.println("\nInfinite loop. Waiting for a message...");
    try (JMSContext jmsContext = connectionFactory.createContext()) {
      while (true) {
        OrderDTO order = jmsContext.createConsumer(topic).receiveBody(OrderDTO.class);
        System.out.println("Order received: " + order);
      }
    }
  }
}

制片人：

public class OrderProducer {

  public static void main(String[] args) throws NamingException {

    if (args.length != 1) {
      System.out.println("usage : enter an amount");
      System.exit(0);
    }

    System.out.println("Sending message with amount = " + args[0]);

    // Creates an orderDto with a total amount parameter
    Float totalAmount = Float.valueOf(args[0]);
    OrderDTO order = new OrderDTO(1234l, new Date(), "Serge Gainsbourg", totalAmount);

    // Gets the JNDI context
    Context jndiContext = new InitialContext();

    // Looks up the administered objects
    ConnectionFactory connectionFactory = (ConnectionFactory) jndiContext.lookup("jms/javaee7/ConnectionFactory");
    Destination topic = (Destination) jndiContext.lookup("jms/javaee7/Topic");

    try (JMSContext jmsContext = connectionFactory.createContext()) {
      // Sends an object message to the topic
      jmsContext.createProducer().setProperty("orderAmount", totalAmount).send(topic, order);
      System.out.println("\nOrder sent : " + order.toString());
    }
  }
}

MDB：

@MessageDriven(mappedName = "jms/javaee7/Topic", activationConfig = {
        @ActivationConfigProperty(propertyName = "acknowledgeMode", propertyValue = "Auto-acknowledge"),
        @ActivationConfigProperty(propertyName = "messageSelector", propertyValue = "orderAmount > 1000")
})
public class ExpensiveOrderMDB implements MessageListener {

  public void onMessage(Message message) {
    try {
      OrderDTO order = message.getBody(OrderDTO.class);
      System.out.println("Expensive order received: " + order.toString());
    } catch (JMSException e) {
      e.printStackTrace();
    }
  }
}

封装在实现Serializable接口

的POJO对象中的msg内容

ExpensiveOrderMDB并且POJO打包在.jar文件中并部署在本地运行的glassfish服务器中。连接和desitination资源由asadmin创建。

问题是：消费者和生产者如何知道本地glassfish服务器上的连接和目的地是否可用于建立连接并发送/接收消息？（创建连接和目标的行对本地glassfish服务器一无所知）

Answer 1

可能有一个jndi.properties文件，其中定义了与glassfish的连接

Java ee jms背后的魔力是什么？

1 个答案: