32. Messaging

The Spring Framework provides extensive support for integrating with messaging systems: from simplified use of the JMS API using JmsTemplate to a complete infrastructure to receive messages asynchronously. Spring AMQP provides a similar feature set for the ‘Advanced Message Queuing Protocol’ and Spring Boot also provides auto-configuration options for RabbitTemplate and RabbitMQ. There is also support for STOMP messaging natively in Spring WebSocket and Spring Boot has support for that through starters and a small amount of auto-configuration. Spring Boot also has support for Apache Kafka.

32.1 JMS

The javax.jms.ConnectionFactory interface provides a standard method of creating a javax.jms.Connection for interacting with a JMS broker. Although Spring needs a ConnectionFactory to work with JMS, you generally won’t need to use it directly yourself and you can instead rely on higher level messaging abstractions (see the relevant section of the Spring Framework reference documentation for details). Spring Boot also auto-configures the necessary infrastructure to send and receive messages.

32.1.1 ActiveMQ support

Spring Boot can also configure a ConnectionFactory when it detects that ActiveMQ is available on the classpath. If the broker is present, an embedded broker is started and configured automatically (as long as no broker URL is specified through configuration).

If you are using spring-boot-starter-activemq the necessary dependencies to connect or embed an ActiveMQ instance are provided, as well as the Spring infrastructure to integrate with JMS.

ActiveMQ configuration is controlled by external configuration properties in spring.activemq.* . For example, you might declare the following section in application.properties :

spring.activemq.broker-url=tcp://192.168.1.210:9876
spring.activemq.user=admin
spring.activemq.password=secret

You can also pool JMS resources by adding a dependency to org.apache.activemq:activemq-pool and configure the PooledConnectionFactory accordingly:

spring.activemq.pool.enabled=true
spring.activemq.pool.max-connections=50

See ActiveMQProperties for more of the supported options. You can also register an arbitrary number of beans implementing ActiveMQConnectionFactoryCustomizer for more advanced customizations.

By default, ActiveMQ creates a destination if it does not exist yet, so destinations are resolved against their provided names.

32.1.2 Artemis support

Spring Boot can auto-configure a ConnectionFactory when it detects that Artemis is available on the classpath. If the broker is present, an embedded broker is started and configured automatically (unless the mode property has been explicitly set). The supported modes are: embedded (to make explicit that an embedded broker is required and should lead to an error if the broker is not available in the classpath), and native to connect to a broker using the netty transport protocol. When the latter is configured, Spring Boot configures a ConnectionFactory connecting to a broker running on the local machine with the default settings.

If you are using spring-boot-starter-artemis the necessary dependencies to connect to an existing Artemis instance are provided, as well as the Spring infrastructure to integrate with JMS. Adding org.apache.activemq:artemis-jms-server to your application allows you to use the embedded mode.

Artemis configuration is controlled by external configuration properties in spring.artemis.* . For example, you might declare the following section in application.properties :

spring.artemis.mode=native
spring.artemis.host=192.168.1.210
spring.artemis.port=9876
spring.artemis.user=admin
spring.artemis.password=secret

When embedding the broker, you can choose if you want to enable persistence, and the list of destinations that should be made available. These can be specified as a comma-separated list to create them with the default options; or you can define bean(s) of type org.apache.activemq.artemis.jms.server.config.JMSQueueConfiguration or org.apache.activemq.artemis.jms.server.config.TopicConfiguration , for advanced queue and topic configurations respectively.

See ArtemisProperties for more of the supported options.

No JNDI lookup is involved at all and destinations are resolved against their names, either using the ‘name’ attribute in the Artemis configuration or the names provided through configuration.

32.1.3 Using a JNDI ConnectionFactory

If you are running your application in an Application Server Spring Boot will attempt to locate a JMS ConnectionFactory using JNDI. By default the locations java:/JmsXA and java:/XAConnectionFactory will be checked. You can use the spring.jms.jndi-name property if you need to specify an alternative location:

spring.jms.jndi-name=java:/MyConnectionFactory

32.1.4 Sending a message

Spring’s JmsTemplate is auto-configured and you can autowire it directly into your own beans:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jms.core.JmsTemplate;
import org.springframework.stereotype.Component;

@Component
public class MyBean {

    private final JmsTemplate jmsTemplate;

    @Autowired
    public MyBean(JmsTemplate jmsTemplate) {
        this.jmsTemplate = jmsTemplate;
    }

    // ...

}

JmsMessagingTemplate can be injected in a similar manner. If a DestinationResolver or MessageConverter beans are defined, they are associated automatically to the auto-configured JmsTemplate .

32.1.5 Receiving a message

When the JMS infrastructure is present, any bean can be annotated with @JmsListener to create a listener endpoint. If no JmsListenerContainerFactory has been defined, a default one is configured automatically. If a DestinationResolver or MessageConverter beans are defined, they are associated automatically to the default factory.

The default factory is transactional by default. If you are running in an infrastructure where a JtaTransactionManager is present, it will be associated to the listener container by default. If not, the sessionTransacted flag will be enabled. In that latter scenario, you can associate your local data store transaction to the processing of an incoming message by adding @Transactional on your listener method (or a delegate thereof). This will make sure that the incoming message is acknowledged once the local transaction has completed. This also includes sending response messages that have been performed on the same JMS session.

The following component creates a listener endpoint on the someQueue destination:

@Component
public class MyBean {

    @JmsListener(destination = "someQueue")
    public void processMessage(String content) {
        // ...
    }

}

Check the Javadoc of @EnableJms for more details.

If you need to create more JmsListenerContainerFactory instances or if you want to override the default, Spring Boot provides a DefaultJmsListenerContainerFactoryConfigurer that you can use to initialize a DefaultJmsListenerContainerFactory with the same settings as the one that is auto-configured.

For instance, the following exposes another factory that uses a specific MessageConverter :

@Configuration
static class JmsConfiguration {

    @Bean
    public DefaultJmsListenerContainerFactory myFactory(
            DefaultJmsListenerContainerFactoryConfigurer configurer) {
        DefaultJmsListenerContainerFactory factory =
                new DefaultJmsListenerContainerFactory();
        configurer.configure(factory, connectionFactory());
        factory.setMessageConverter(myMessageConverter());
        return factory;
    }

}

Then you can use in any @JmsListener -annotated method as follows:

@Component
public class MyBean {

    @JmsListener(destination = "someQueue", containerFactory="myFactory")
    public void processMessage(String content) {
        // ...
    }

}

32.2 AMQP

The Advanced Message Queuing Protocol (AMQP) is a platform-neutral, wire-level protocol for message-oriented middleware. The Spring AMQP project applies core Spring concepts to the development of AMQP-based messaging solutions. Spring Boot offers several conveniences for working with AMQP via RabbitMQ, including the spring-boot-starter-amqp ‘Starter’.

32.2.1 RabbitMQ support

RabbitMQ is a lightweight, reliable, scalable and portable message broker based on the AMQP protocol. Spring uses RabbitMQ to communicate using the AMQP protocol.

RabbitMQ configuration is controlled by external configuration properties in spring.rabbitmq.* . For example, you might declare the following section in application.properties :

spring.rabbitmq.host=localhost
spring.rabbitmq.port=5672
spring.rabbitmq.username=admin
spring.rabbitmq.password=secret

See RabbitProperties for more of the supported options.

Check Understanding AMQP, the protocol used by RabbitMQ for more details.

32.2.2 Sending a message

Spring’s AmqpTemplate and AmqpAdmin are auto-configured and you can autowire them directly into your own beans:

import org.springframework.amqp.core.AmqpAdmin;
import org.springframework.amqp.core.AmqpTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component
public class MyBean {

    private final AmqpAdmin amqpAdmin;
    private final AmqpTemplate amqpTemplate;

    @Autowired
    public MyBean(AmqpAdmin amqpAdmin, AmqpTemplate amqpTemplate) {
        this.amqpAdmin = amqpAdmin;
        this.amqpTemplate = amqpTemplate;
    }

    // ...

}

RabbitMessagingTemplate can be injected in a similar manner. If a MessageConverter bean is defined, it is associated automatically to the auto-configured AmqpTemplate .

Any org.springframework.amqp.core.Queue that is defined as a bean will be automatically used to declare a corresponding queue on the RabbitMQ instance if necessary.

You can enable retries on the AmqpTemplate to retry operations, for example in the event the broker connection is lost. Retries are disabled by default.

32.2.3 Receiving a message

When the Rabbit infrastructure is present, any bean can be annotated with @RabbitListener to create a listener endpoint. If no RabbitListenerContainerFactory has been defined, a default one is configured automatically. If a MessageConverter or MessageRecoverer beans are defined, they are associated automatically to the default factory.

The following component creates a listener endpoint on the someQueue queue:

@Component
public class MyBean {

    @RabbitListener(queues = "someQueue")
    public void processMessage(String content) {
        // ...
    }

}

Check the Javadoc of @EnableRabbit for more details.

If you need to create more RabbitListenerContainerFactory instances or if you want to override the default, Spring Boot provides a SimpleRabbitListenerContainerFactoryConfigurer that you can use to initialize a SimpleRabbitListenerContainerFactory with the same settings as the one that is auto-configured.

For instance, the following exposes another factory that uses a specific MessageConverter :

@Configuration
static class RabbitConfiguration {

    @Bean
    public SimpleRabbitListenerContainerFactory myFactory(
            SimpleRabbitListenerContainerFactoryConfigurer configurer) {
        SimpleRabbitListenerContainerFactory factory =
                new SimpleRabbitListenerContainerFactory();
        configurer.configure(factory, connectionFactory);
        factory.setMessageConverter(myMessageConverter());
        return factory;
    }

}

Then you can use in any @RabbitListener -annotated method as follows:

@Component
public class MyBean {

    @RabbitListener(queues = "someQueue", containerFactory="myFactory")
    public void processMessage(String content) {
        // ...
    }

}

You can enable retries to handle situations where your listener throws an exception. By default RejectAndDontRequeueRecoverer is used but you can define a MessageRecoverer of your own. When retries are exhausted, the message will be rejected and either dropped or routed to a dead-letter exchange if the broker is configured so. Retries are disabled by default.

If retries are not enabled and the listener throws an exception, by default the delivery will be retried indefinitely. You can modify this behavior in two ways; set the defaultRequeueRejected property to false and zero re-deliveries will be attempted; or, throw an AmqpRejectAndDontRequeueException to signal the message should be rejected. This is the mechanism used when retries are enabled and the maximum delivery attempts are reached.

32.3 Apache Kafka Support

Apache Kafka is supported by providing auto-configuration of the spring-kafka project.

Kafka configuration is controlled by external configuration properties in spring.kafka.* . For example, you might declare the following section in application.properties :

spring.kafka.bootstrap-servers=localhost:9092
spring.kafka.consumer.group-id=myGroup

See KafkaProperties for more of the supported options.

32.3.1 Sending a Message

Spring’s KafkaTemplate is auto-configured and you can autowire them directly in your own beans:

@Component
public class MyBean {

	private final KafkaTemplate kafkaTemplate;

	@Autowired
	public MyBean(KafkaTemplate kafkaTemplate) {
		this.kafkaTemplate = kafkaTemplate;
	}

	// ...

}

32.3.2 Receiving a Message

When the Apache Kafka infrastructure is present, any bean can be annotated with @KafkaListener to create a listener endpoint. If no KafkaListenerContainerFactory has been defined, a default one is configured automatically with keys defined in spring.kafka.listener.* .

The following component creates a listener endpoint on the someTopic topic:

@Component
public class MyBean {

    @KafkaListener(topics = "someTopic")
    public void processMessage(String content) {
        // ...
    }

}

32.3.3 Additional Kafka Properties

The properties supported by auto configuration are shown in Appendix A, Common application properties. Note that these properties (hyphenated or camelCase) map directly to the Apache Kafka dotted properties for the most part, refer to the Apache Kafka documentation for details.

The first few of these properties apply to both producers and consumers, but can be specified at the producer or consumer level if you wish to use different values for each. Apache Kafka designates properties with an importance: HIGH, MEDIUM and LOW. Spring Boot auto configuration supports all HIGH importance properties, some selected MEDIUM and LOW, and any that do not have a default value.

Only a subset of the properties supported by Kafka are available via the KafkaProperties class. If you wish to configure the producer or consumer with additional properties that are not directly supported, use the following:

spring.kafka.properties.foo.bar=baz

This sets the common foo.bar Kafka property to baz .

These properties will be shared by both the consumer and producer factory beans. If you wish to customize these components with different properties, such as to use a different metrics reader for each, you can override the bean definitions, as follows:

@Configuration
public static class CustomKafkaBeans {

    /**
     * Customized ProducerFactory bean.
     * @param properties the kafka properties.
     * @return the bean.
     */
    @Bean
    public ProducerFactory<?, ?> kafkaProducerFactory(KafkaProperties properties) {
        Map<String, Object> producerProperties = properties.buildProducerProperties();
        producerProperties.put(CommonClientConfigs.METRIC_REPORTER_CLASSES_CONFIG,
                MyProducerMetricsReporter.class);
        return new DefaultKafkaProducerFactory<Object, Object>(producerProperties);
    }

    /**
     * Customized ConsumerFactory bean.
     * @param properties the kafka properties.
     * @return the bean.
     */
    @Bean
    public ConsumerFactory<?, ?> kafkaConsumerFactory(KafkaProperties properties) {
        Map<String, Object> consumerProperties = properties.buildConsumerProperties();
        consumerProperties.put(CommonClientConfigs.METRIC_REPORTER_CLASSES_CONFIG,
                MyConsumerMetricsReporter.class);
        return new DefaultKafkaConsumerFactory<Object, Object>(consumerProperties);
    }

}
Updated at: 7 months ago
31.1.11. NoneTable of content33. Calling REST services