# JMS Client for Confluent Platform Java Message Service (JMS) is a widely used messaging API that is included as part of the Java Platform, Enterprise Edition. Confluent JMS Client (`kafka-jms-client`) is an implementation of the [JMS 1.1 provider interface](https://docs.oracle.com/javaee/6/api/javax/jms/package-summary.html) that allows Apache Kafka® or Confluent to be used as a JMS message broker. `[kafka-jms-client] <--- kafka protocol ---> [kafka broker]` Applications written using the Confluent `kafka-jms-client` can exchange messages with other application written using `kafka-jms-client` as well as any application that produces or consumes messages using any other Kafka client library. The purpose of this client is to allow existing applications written to the JMS API to be able to publish and subscribe to Kafka as a replacement for any other JMS broker. If you are interested in integrating Kafka with an existing JMS broker (that is, without replacing it) then you are encouraged to look at the [Kafka Connect Rest API](https://developer.confluent.io/learn-kafka/kafka-connect/rest-api/) or any pre-built Kafka Source or Sink Connectors for JMS. If you are interested in writing new Java applications then you are encouraged to use the Java Kafka Producer/Consumer APIs as they provide advanced features not available when using the `kafka-jms-client`. #### WARNING The JMS Client will be deprecated in Confluent Platform version 8.0 and may be removed from use in both Confluent Platform and Confluent Cloud. ## JMS 1.1 Compatibility Where possible, the Kafka JMS Client is a complete implementation of the JMS 1.1 specification. However there are some JMS concepts that either do not map 1:1 to Kafka, or simply do not make sense at all in Kafka (such as non-persistent messages). JMS brokers typically provide distinct [Topic](https://docs.oracle.com/javaee/6/api/javax/jms/Topic.html) and [Queue](https://docs.oracle.com/javaee/6/api/javax/jms/Queue.html) functionality that reflects the topic and queue functionality in the JMS Specification. By contrast, Kafka provides only one abstraction - partitioned topics - which are actually distributed commit logs and behave differently than the traditional messaging system notion of a topic. In practice, Kafka topics can mimic the behavior of either topics or queues in the traditional messaging system sense. Additional notes on JMS 1.1 compatibility are outlined below. ### Features Both JMS messaging models are supported: * Publish/Subscribe (Topics) * Point-to-Point (Queues) All JMS message types are supported including: * `TextMessage` * `BytesMessage` * `MapMessage` * `StreamMessage` * `ObjectMessage` Treatment of JMS header values: * `JMSDestination` - Set (overwritten) to on send and available in message at the destination. * `JMSDeliveryMode` - Set (overwritten) to DEAULT_DELIVERY_MODE (PERSISTED) on send. * `JMSExpiration` - Ignored. Overwritten with 0 on send. * `JMSPriority` - Ignored. Set (overwritten) with DEFAULT_PRIORITY (4) on send. * `JMSMessageID` - Set (overwritten) with a unique id for the message on send and available in message at destination. * `JMSTimestamp` - Set (overwritten) on message send and transmitted to destination if this has not been disabled using `MessageProducer.setDisableMessageTimestamp`. * `JMSCorrelationID` - Value set by user is transmitted to destination. * `JMSReplyTo` - Value set by user is transmitted to destination. * `JMSType` - Value set by user is transmitted to destination. * `JMSRedelivered` - Ignored. Set (overwritten) to false on send. Only durable topics/queues are supported. ### Unsupported Features The following functionality has either limited support or no support: #### Session | Method | Notes | |---------------------------------------------------------|---------------------------------------------------------------------------------| | createDurableSubscriber(Topic, String) | Durable Subscribers are not supported. | | createDurableSubscriber(Topic, String, String, boolean) | Durable Subscribers are not supported. | | getMessageListener() | Session based MessageListeners are not supported. | | setMessageListener(MessageListener) | Session based MessageListeners are not supported. | | rollback() | Transactions are not supported by Kafka. | | recover() | Transactions are not supported by Kafka | | commit() | Transactions are not supported by Kafka. | | createBrowser(Queue, String) | QueueBrowsers with message selectors are not supported. | | unsubscribe(String) | Durable Subscribers are not supported. | | createConsumer(Destination, String) | Message selectors are not supported. An exception will be thrown if one is set. | | createConsumer(Destination, String, boolean) | Message selectors are not supported. An exception will be thrown if one is set. | | createTemporaryTopic() | Kafka does not have a concept of a temporary topic. | | getTransacted() | Transactions are not supported. This will always return false. | | createTemporaryQueue() | Kafka does not have a concept of a temporary topic. | ConnectionFactory ^^^^^^^^^^^^^^^^^^^^^^^^~ | Method | Notes | |----------------------------------|-------------------------------------------------------------------------------------| | createConnection(String, String) | Not supported. Authentication is only supported via Kafka configuration properties. | Connection ^^^^^^^^^^^^~~ | Method | Notes | |---------------------|--------------------------------------------------------------------------------------------------------------| | setClientID(String) | Setting the client id is only supported by using client.id in the settings passed to KafkaConnectionFactory. | ## JMS Client Installation Prerequisites : If you are using Confluent Platform, see the system requirements. ### Installation The JMS Client is a library that you use from within your Java applications. To reference `kafka-jms-client` in a Maven-based project, first add the Confluent Maven repository to your `pom.xml`: ```none confluent http://packages.confluent.io/maven/ ``` Then add a dependency on the Confluent JMS Client and the JMS API specification: ```bash io.confluent kafka-jms-client 8.3.1 org.apache.geronimo.specs geronimo-jms_1.1_spec 1.1 ``` If you don’t use Maven, you can download the JMS Client JAR file directly by navigating to the following URL. ```bash http://packages.confluent.io/maven/io/confluent/kafka-jms-client/8.3.1/kafka-jms-client -8.3.1.jar ``` If you require a “fat” JAR (one that includes the JMS Client and all of its dependencies), you can make one by following the instructions in [Appendix 1 - Creating a Shaded Fat JAR](#appendix-1). ### Example Usage of `kafka-jms-client` is similar to the JMS API. The following example program uses a `KafkaConnectionFactory` instance to create JMS compliant `Connection`, `Session` and `MessageProducer` objects. The `MessageProducer` is then used to send 50 `TextMessage` messages to the Apache Kafka® topic `test-queue`, which is acting as a queue. A `MessageConsumer` is then created and used to read back these messages. ```java import java.util.Properties; import javax.jms.Connection; import javax.jms.ConnectionFactory; import javax.jms.Destination; import javax.jms.JMSException; import javax.jms.Message; import javax.jms.MessageConsumer; import javax.jms.MessageProducer; import javax.jms.Session; import javax.jms.TextMessage; import io.confluent.kafka.jms.JMSClientConfig; import io.confluent.kafka.jms.KafkaConnectionFactory; public class App { public static void main(String[] args) throws JMSException { Properties settings = new Properties(); settings.put(JMSClientConfig.CLIENT_ID_CONFIG, "test-client-2"); settings.put(JMSClientConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092"); settings.put(JMSClientConfig.ZOOKEEPER_CONNECT_CONF, "localhost:2181"); ConnectionFactory connectionFactory = new KafkaConnectionFactory(settings); Connection connection = connectionFactory.createConnection(); Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE); Destination testQueue = session.createQueue("test-queue"); MessageProducer producer = session.createProducer(testQueue); for (int i=0; i<50; i++) { TextMessage message = session.createTextMessage(); message.setText("This is a text message"); producer.send(message); } MessageConsumer consumer = session.createConsumer(testQueue); while (true) { TextMessage message = (TextMessage)consumer.receive(); System.out.println(message.getText()); } } } ``` ### Appendix 1 - Creating a Shaded Fat JAR In some scenarios, it is useful to have a “fat” JAR that bundles the JMS Client together with all of its dependencies in a single file. Confluent does not distribute the JMS Client in this form, but you can build a fat JAR yourself easily enough: 1. Copy the `pom.xml` below into an empty directory. 2. Execute the Maven command `mvn package`. The resulting artifact will be placed in the `target` directory along side the `pom.xml` file. Note: In addition to bundling dependencies, the provided `pom.xml` file *shades* them under the namespace `confluent.shaded.` to avoid potential namespace clashes. ```bash 4.0.0 io.confluent kafka-jms-client-fat 8.3.1 confluent http://packages.confluent.io/maven/ io.confluent kafka-jms-client 8.3.1 org.apache.maven.plugins maven-shade-plugin 2.4.3 package shade org.I0Itec. confluent.shaded.org.I0Itec. com.yammer.metrics. confluent.shaded.com.yammer.metrics. joptsimple confluent.shaded.joptsimple org.apache.zookeeper. confluent.shaded.org.apache.zookeeper. org.apache.jute. confluent.shaded.org.apache.jute. org.apache.kafka. confluent.shaded.org.apache.kafka. org.apache.log4j. confluent.shaded.org.apache.log4j. com.google.common. confluent.shaded.com.google.common. com.google.thirdparty. confluent.shaded.com.google.thirdparty. com.fasterxml.jackson. confluent.shaded.com.fasterxml.jackson. net.jpountz. confluent.shaded.net.jpountz. org.xerial.snappy. confluent.shaded.org.xerial.snappy. org.jose4j. confluent.shaded.org.jose4j. io.confluent.common. confluent.shaded.io.confluent.common. io.confluent.license. confluent.shaded.io.confluent.license. kafka. confluent.shaded.kafka. scala confluent.shaded.scala. src/main/resources true ``` ## Suggested Reading - [Installation, Download, and Usage for the JMS Client](#client-jms-installation) - [JMS Client Development Guide for Confluent Platform](dev-guide.md#client-jms-developing) - [JMS Client Overview](#client-jms)