Today you’re going to see how to implement a MessageConverter using Spring JMS.
The best part?
It’s really easy to do.
So let’s get down to business
If you want to learn more about Spring JMS – head on over to the Spring JMS tutorials page.
1. What is a Message Converter?
A MessageConverter specifies how to convert between Java objects and JMS messages.
Spring JMS comes with a number of implementations that are ready to use. By default, the SimpleMessageConverter is used by the framework. It is able to handle TextMessages, BytesMessages, MapMessages, and ObjectMessages.
Let’s build an example to show how you can use a message converter with Spring JMS. We start from a previous Spring with JMS example. We will adapt it so that we can send a Person object that gets converted to/from JSON.
Note that Spring JMS ships with a
MappingJackson2MessageConverterthat converts messages to and from JSON. We will not use it and create our own custom implementation instead.
2. General Project Overview
We will use the following tools/frameworks:
- Spring JMS 5.1
- Spring Boot 2.1
- ActiveMQ 5.15
- Maven 3.6
Our project has the following directory structure:
3. Create a Custom JSON Message Converter
First, we define a simple Person class that contains a name and age. It is a simple POJO with the needed constructors and getters/setters.
package com.codenotfound.jms;
public class Person {
private String name;
private int age;
public Person() {
super();
}
public Person(String name, int age) {
super();
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "person[name=" + name + ", age=" + age + "]";
}
}Next, create a PersonMessageConverter class that implements the MessageConverter interface.
You need to implement two methods: toMessage() and fromMessage(). These specify how the conversion between the Person object and JMS message is done.
In the toMessage() method we create a TextMessage. As payload, we set the JSON String representation of a Person.
The fromMessage() method converts the JSON String from a JMS message into a Person.
The conversion between a Java object and JSON is done using a Jackson ObjectMapper.
Annotate the class with @Component so that Spring registers the class as a Bean. When Spring Boot detects this class it is auto-configured on both the JmsTemplate and DefaultJmsListenerContainerFactory.
You can also set the
MessageConverteron theJmsTemplateandMessageListenerContainerusingsetMessageConverter(). But this means you need to create these Beans as we saw in a previous Spring JMS Example.
package com.codenotfound.jms;
import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.Session;
import javax.jms.TextMessage;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.jms.support.converter.MessageConverter;
import org.springframework.stereotype.Component;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
@Component
public class PersonMessageConverter implements MessageConverter {
private static final Logger LOGGER =
LoggerFactory.getLogger(PersonMessageConverter.class);
ObjectMapper mapper;
public PersonMessageConverter() {
mapper = new ObjectMapper();
}
@Override
public Message toMessage(Object object, Session session)
throws JMSException {
Person person = (Person) object;
String payload = null;
try {
payload = mapper.writeValueAsString(person);
LOGGER.info("outbound json='{}'", payload);
} catch (JsonProcessingException e) {
LOGGER.error("error converting form person", e);
}
TextMessage message = session.createTextMessage();
message.setText(payload);
return message;
}
@Override
public Object fromMessage(Message message) throws JMSException {
TextMessage textMessage = (TextMessage) message;
String payload = textMessage.getText();
LOGGER.info("inbound json='{}'", payload);
Person person = null;
try {
person = mapper.readValue(payload, Person.class);
} catch (Exception e) {
LOGGER.error("error converting to person", e);
}
return person;
}
}To wrap up, make sure to also change the Sender and Receiver so that a Person object is sent/received.
4. Test the JMS Message Converter
To test the message converter, create a Person and send it to the converter.q queue.
package com.codenotfound.jms;
import static org.assertj.core.api.Assertions.assertThat;
import java.util.concurrent.TimeUnit;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.annotation.DirtiesContext;
import org.springframework.test.context.junit4.SpringRunner;
@RunWith(SpringRunner.class)
@SpringBootTest
@DirtiesContext
public class SpringJmsApplicationTest {
@Autowired
private Sender sender;
@Autowired
private Receiver receiver;
@Test
public void testReceive() throws Exception {
Person person = new Person("John Doe", 20);
sender.send("converter.q", person);
receiver.getLatch().await(10000, TimeUnit.MILLISECONDS);
assertThat(receiver.getLatch().getCount()).isEqualTo(0);
}
}Open a command prompt in the root directory of the project. Execute the following Maven command:
mvn testThe log output shows that the message is converted to/from a JSON representation.
. ____ _ __ _ _
/// / ___'_ __ _ _(_)_ __ __ _ / / / /
( ( )/___ | '_ | '_| | '_ // _` | / / / /
/// ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_/__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.1.5.RELEASE)
2019-05-30 17:13:58.069 INFO 596 --- [ main] c.c.jms.SpringJmsApplicationTest : Starting SpringJmsApplicationTest on DESKTOP-2RB3C1U with PID 596 (started by Codenotfound in C:/Users/Codenotfound/repos/spring-jms/spring-jms-message-converter)
2019-05-30 17:13:58.071 INFO 596 --- [ main] c.c.jms.SpringJmsApplicationTest : No active profile set, falling back to default profiles: default
2019-05-30 17:13:59.844 INFO 596 --- [ main] o.apache.activemq.broker.BrokerService : Using Persistence Adapter: MemoryPersistenceAdapter
2019-05-30 17:13:59.931 INFO 596 --- [ JMX connector] o.a.a.broker.jmx.ManagementContext : JMX consoles can connect to service:jmx:rmi:///jndi/rmi://localhost:1099/jmxrmi
2019-05-30 17:14:00.019 INFO 596 --- [ main] o.apache.activemq.broker.BrokerService : Apache ActiveMQ 5.15.9 (localhost, ID:DESKTOP-2RB3C1U-59651-1559229239872-0:1) is starting
2019-05-30 17:14:00.026 INFO 596 --- [ main] o.apache.activemq.broker.BrokerService : Apache ActiveMQ 5.15.9 (localhost, ID:DESKTOP-2RB3C1U-59651-1559229239872-0:1) started
2019-05-30 17:14:00.026 INFO 596 --- [ main] o.apache.activemq.broker.BrokerService : For help or more information please see: http://activemq.apache.org
2019-05-30 17:14:00.057 INFO 596 --- [ main] o.a.activemq.broker.TransportConnector : Connector vm://localhost started
2019-05-30 17:14:00.116 INFO 596 --- [ main] c.c.jms.SpringJmsApplicationTest : Started SpringJmsApplicationTest in 2.491 seconds (JVM running for 3.467)
2019-05-30 17:14:00.456 INFO 596 --- [ main] com.codenotfound.jms.Sender : sending person='person[name=John Doe, age=20]' to destination='converter.q'
2019-05-30 17:14:00.508 INFO 596 --- [ main] c.c.jms.PersonMessageConverter : outbound json='{"name":"John Doe","age":20}'
2019-05-30 17:14:00.519 INFO 596 --- [enerContainer-1] c.c.jms.PersonMessageConverter : inbound json='{"name":"John Doe","age":20}'
2019-05-30 17:14:00.549 INFO 596 --- [enerContainer-1] com.codenotfound.jms.Receiver : received person='person[name=John Doe, age=20]'
2019-05-30 17:14:01.566 INFO 596 --- [ main] o.a.activemq.broker.TransportConnector : Connector vm://localhost stopped
2019-05-30 17:14:01.566 INFO 596 --- [ main] o.apache.activemq.broker.BrokerService : Apache ActiveMQ 5.15.9 (localhost, ID:DESKTOP-2RB3C1U-59651-1559229239872-0:1) is shutting down
2019-05-30 17:14:01.581 INFO 596 --- [ main] o.apache.activemq.broker.BrokerService : Apache ActiveMQ 5.15.9 (localhost, ID:DESKTOP-2RB3C1U-59651-1559229239872-0:1) uptime 2.090 seconds
2019-05-30 17:14:01.581 INFO 596 --- [ main] o.apache.activemq.broker.BrokerService : Apache ActiveMQ 5.15.9 (localhost, ID:DESKTOP-2RB3C1U-59651-1559229239872-0:1) is shutdown
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 4.571 s - in com.codenotfound.jms.SpringJmsApplicationTest
[INFO]
[INFO] Results:
[INFO]
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 9.370 s
[INFO] Finished at: 2019-05-30T17:14:02+02:00
[INFO] ------------------------------------------------------------------------
If you would like to run the above code sample you can get the full source code here.
In this tutorial, you learned how to create a custom Spring JMS message converter.
Let me know if you found this example useful.
Thanks!
原创文章，作者：ItWorker，如若转载，请注明出处：https://blog.ytso.com/tech/java/271581.html