java - 如何序列化您在 JMS 模板 Convert 和 Send 方法中发送的自定义对象

Question

我正在使用下面提到的代码发布到一个主题中。它的格式为 convertAndSend(Destination destination, Object message)

    Event event;
    jmsTemplate.convertAndSend(topic, event); 

我现在的Event界面是这样的，

    public interface Event {

    public boolean isEmpty();

    public AcEventDatafileTransaction getDatafileTransaction();

    public AcEventObjectTransaction getObjectTransaction();

    boolean isDatafileTransaction();

    boolean isObjectTransaction();

    boolean isRdbmsTransaction();

    String getTransactionId();

    }

它的实现是这样的，

    public class EventPublisherImpl implements Event {
    private final AcTransactionRecord transactionRecord;
    private final Ac ac;
    private final String[] actualTemplates;
    private final String[] curveTemplates;

    public AcEventPublisherImpl(final Ac ac, 
                                final String[] actualTemplates, 
                                final String[] curveTemplates, 
                                final AcTransactionRecord acTransactionRecord) {
        this.ac = ac;
        this.transactionRecord = acTransactionRecord;
        this.actualTemplates = actualTemplates;
        this.curveTemplates = curveTemplates;
    }

    @Override
    public boolean isEmpty() {
        return transactionRecord.isEmpty();
    }

    @Override
    public AcEventDatafileTransaction getDatafileTransaction() {
        if (isDatafileTransaction()) {
          return new AcEventDatafileTransactionPublisherImpl(transactionRecord.getDatafileTransaction());
        }
        return null;
    }


    @Override
    public AcEventObjectTransaction getObjectTransaction() {
        if (isObjectTransaction()) {
          return new AcEventObjectTransactionPublisherImpl(ac, actualTemplates, curveTemplates, transactionRecord.getObjectOperations());
        }
        return null;
    }

    @Override
    public boolean isDatafileTransaction() {
        return transactionRecord.getType() == AcTransactionRecord.DATAFILE_TRANS;
    }

    @Override
    public boolean isObjectTransaction() {
        return transactionRecord.getType() == AcTransactionRecord.OBJECT_TRANS;
    }

    @Override
    public boolean isRdbmsTransaction() {      
      return transactionRecord.getType() == AcTransactionRecord.RDBMS_TRANS;
    }

    @Override
    public String getTransactionId() {
        if (transactionRecord != null) {
            return Integer.toString(transactionRecord.getNumber());
        }
        return "";
    }
  }

如何将其转换为可序列化的形式？

我的全部目标是将事件对象发布到主题中。为此，我正在使用 convertAndSend 方法。该方法需要一个序列化类的对象，而我目前没有。这就是我想要实现的目标。我查看了使用消息转换器 https://examples.javacodegeeks.com/enterprise-java/spring/spring-framework-jmstemplate-example/ 序列化具有少量属性的类的示例

请通过代码建议一种方法或指出适当的示例以及这对我有何帮助。

Answer 1

The overloaded methods convertAndSend() and receiveAndConvert() in JmsTemplate delegate the conversion process to an instance of the MessageConverter interface. This interface defines a simple contract to convert between Java objects and JMS messages. The default implementation SimpleMessageConverter supports conversion between String and TextMessage, byte[] and BytesMesssage, and java.util.Map and MapMessage.

因此，为了支持自定义类型，我们必须创建实现 MessageConverter 的自定义转换器，以将 Event 对象转换为支持的消息类型之一。最简单的解决方案是注册spring提供的MappingJackson2MessageConverter，它支持将对象转换为json形式的TextMessage。

@Bean // Serialize message content to json using TextMessage
public MessageConverter jacksonJmsMessageConverter() {
    MappingJackson2MessageConverter converter = new MappingJackson2MessageConverter();
    converter.setTargetType(MessageType.TEXT);
    converter.setTypeIdPropertyName("_type");
    return converter;
}

如果您想创建自己的转换器，您可以查看如何在源代码上完成序列化过程。

要接收消息，最简单的方法是使用@JmsListener注解，spring会使用注册的转换器隐式地将消息转换成它的java类型

@Component
public class Receiver {
  @JmsListener(destination = "dest")
  public void receiveMessage(Event event) {
    // do whatever you need with the event
  }
}

另一种方法是使用javax.jms.MessageListener，但您需要自己手动转换消息。

@Component
public class ExampleListener implements MessageListener {

@Autowired
private ObjectMapper objectMapper;

public void onMessage(Message message) {
    if (message instanceof TextMessage) {// we set the converter targetType to text
        try {
            String json = ((TextMessage) message).getText(); // here you have your event object as json string
            Event event = objectMapper.readValue(json, Event.class); // convert back to event object
        }
        catch (JMSException ex) {
            throw new RuntimeException(ex);
        }
    }
    else {
        throw new IllegalArgumentException("Message must be of type TextMessage");
    }
}

引用:

• MappingJackson2MessageConverter
• https://spring.io/guides/gs/messaging-jms/