spring-jms
Getting Started with Spring JMS
1. Overview
2. Maven Dependency
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jms</artifactId>
<version>4.3.3.RELEASE</version>
</dependency>The newest version of the artifact can be found here.
3. The JmsTemplate
JmsTemplate class handles the creation and releasing of resources when sending or synchronously receiving messages.
Hence the class that uses this JmsTemplate only needs to implement callback interfaces as specified in the method definition.
Starting with Spring 4.1, the JmsMessagingTemplate is built on top of JmsTemplate which provides an integration with the messaging abstraction, i.e., org.springframework.messaging.Message. This, in turn, allows us to create a message to send in a generic manner.
4. Connection Management
A ConnectionFactory is one of the JMS administered objects which are preconfigured by an administrator. A client with the help of the configuration will make the connection with a JMS provider.
Spring provides 2 types of ConnectionFactory:
-
SingleConnectionFactory – is an implementation of ConnectionFactory interface, that will return the same connection on all createConnection() calls and ignore calls to close()
-
CachingConnectionFactory – extends the functionality of the SingleConnectionFactory and adds enhances it with a caching of Sessions, MessageProducers, and MessageConsumers
5. Destination Management
As discussed above, along with the ConnectionFactory, destinations are also JMS administered objects and can be stored and retrieved from a JNDI.
Spring provides generic resolvers like DynamicDestinationResolver and specific resolvers such as JndiDestinationResolver.
The JmsTemplate will delegate the resolution of the destination name to one of the implementations basing on our selection.
It will also provide a property called defaultDestination – which will be used with send and receive operations that do not refer to a specific destination.
6. Message Conversion
The default conversion strategy used by JmsTemplate for both ConvertAndSend() and ReceiveAndConvert() operations is the SimpleMessageConverter class.
The SimpleMessageConverter is able to handle TextMessages, BytesMessages, MapMessages, and ObjectMessages. This class implements the MessageConverter interface.
Apart from SimpleMessageConverter, Spring JMS provides some other MessageConverter classes out of the box like MappingJackson2MessageConverter, MarshallingMessageConverter, MessagingMessageConverter.
Moreover, we can create custom message conversion functionality simply by implementing the MessageConverter interface’s toMessage() and FromMessage() methods.
Let us see a sample code snippet on implementing a custom MessageConverter,
public class SampleMessageConverter implements MessageConverter {
public Object fromMessage(Message message)
throws JMSException, MessageConversionException {
//...
}
public Message toMessage(Object object, Session session)
throws JMSException, MessageConversionException {
//...
}
}7. Sample Spring JMS
The default method for sending the message is JmsTemplate.send(). It has two key parameters of which, the first parameter is the JMS destination and the second parameter is an implementation of MessageCreator. The JmsTemplate uses the MessageCreator‘s callback method createMessage() for constructing the message.
JmsTemplate.send() is good for sending plain text messages but in order to send custom messages, JmsTemplate has another method called convertAndSend().
We can see below the implementation of these methods:
public class SampleJmsMessageSender {
private JmsTemplate jmsTemplate;
private Queue queue;
// setters for jmsTemplate & queue
public void simpleSend() {
jmsTemplate.send(queue, s -> s.createTextMessage("hello queue world"));
} public void sendMessage(Employee employee) {
System.out.println("Jms Message Sender : " + employee);
Map<String, Object> map = new HashMap<>();
map.put("name", employee.getName()); map.put("age", employee.getAge());
jmsTemplate.convertAndSend(map);
}
}Below is the message receiver class, we call it as Message-Driven POJO (MDP). We can see that the class SampleListener is implementing the MessageListener interface and provides the text specific implementation for the interface method onMessage().
Apart from onMessage() method, our SampleListener class also called a method receiveAndConvert() for receiving custom messages:
public class SampleListener implements MessageListener {
public JmsTemplate getJmsTemplate() {
return getJmsTemplate();
}
public void onMessage(Message message) {
if (message instanceof TextMessage) {
try {
String msg = ((TextMessage) message).getText();
System.out.println("Message has been consumed : " + msg);
} catch (JMSException ex) {
throw new RuntimeException(ex);
}
} else {
throw new IllegalArgumentException("Message Error");
}
}
public Employee receiveMessage() throws JMSException {
Map map = (Map) getJmsTemplate().receiveAndConvert();
return new Employee((String) map.get("name"), (Integer) map.get("age"));
}
}We saw how to implement MessageListener and below we see the configuration in Spring application context:
<bean id="messageListener" class="com.baeldung.spring.jms.SampleListener" />
<bean id="jmsContainer"
class="org.springframework.jms.listener.DefaultMessageListenerContainer">
<property name="connectionFactory" ref="connectionFactory"/>
<property name="destinationName" ref="IN_QUEUE"/>
<property name="messageListener" ref="messageListener" />
</bean>DefaultMessageListenerContainer is the default message listener container Spring provides along with many other specialized containers.
8. Basic Configuration with Java Annotations
The @JmsListener is the only annotation required to convert a method of a normal bean into a JMS listener endpoint. Spring JMS provides many more annotations to ease the JMS implementation.
We can see some of the sample classes annotated below:
@JmsListener(destination = "myDestination")
public void SampleJmsListenerMethod(Message<Order> order) { ... }In order to add multiple listeners to a single method we just need to add multiple @JmsListener annotations.
We need to add the @EnableJms annotation to one of our configuration classes to support the @JmsListener annotated methods:
@Configuration
@EnableJms
public class AppConfig {
@Bean
public DefaultJmsListenerContainerFactory jmsListenerContainerFactory() {
DefaultJmsListenerContainerFactory factory
= new DefaultJmsListenerContainerFactory();
factory.setConnectionFactory(connectionFactory());
return factory;
}
}9. Error Handler
Let’s first implement the org.springframework.util.ErrorHandler interface:
@Service
public class SampleJmsErrorHandler implements ErrorHandler {
// ... logger
@Override
public void handleError(Throwable t) {
LOG.warn("In default jms error handler...");
LOG.error("Error Message : {}", t.getMessage());
}
}Note that we have overridden the handleError() method, which simply logs the error message.
And then, we need to reference our error handler service in the DefaultJmsListenerConnectionFactory using the setErrorHandler() method:
@Bean
public DefaultJmsListenerContainerFactorybjmsListenerContainerFactory() {
DefaultJmsListenerContainerFactory factory
= new DefaultJmsListenerContainerFactory();
factory.setConnectionFactory(connectionFactory());
factory.setErrorHandler(sampleJmsErrorHandler);
return factory;
}With this, our configured error handler will now catch any unhandled exceptions and log the message.
Optionally, we can also configure the error handler using the plain-old XML configurations by updating our appContext.xml:
<bean id="sampleJmsErrorHandler"
class="com.baeldung.spring.jms.SampleJmsErrorHandler" />
<bean id="jmsContainer"
class="org.springframework.jms.listener.DefaultMessageListenerContainer">
<property name="connectionFactory" ref="connectionFactory" />
<property name="destinationName" value="IN_QUEUE" />
<property name="messageListener" ref="messageListener" />
<property name="errorHandler" ref="sampleJmsErrorHandler" />
</bean>10. Conclusion
In this tutorial, we discussed the configuration and basic concepts of Spring JMS. We also had a brief look at the Spring-specific JmsTemplate classes which are used for sending and receiving messages.
You can find the code implementation in the GitHub project.
