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Chapter 9. Mixing JMS and REST

9.1. JMS Producers - REST Consumers
9.2. REST Producers - JMS Consumers

The HornetQ REST interface supports mixing JMS and REST producres and consumers. You can send an ObjectMessage through a JMS Producer, and have a REST client consume it. You can have a REST client POST a message to a topic and have a JMS Consumer receive it. Some simple transformations are supported if you have the correct RESTEasy providers installed.

If you have a JMS producer, the HornetQ REST interface only supports ObjectMessage type. If the JMS producer is aware that there may be REST consumers, it should set a JMS property to specify what Content-Type the Java object should be translated into by REST clients. The HornetQ REST server will use RESTEasy content handlers (MessageBodyReader/Writers) to transform the Java object to the type desired. Here's an example of a JMS producer setting the content type of the message.

ObjectMessage message = session.createObjectMessage();
message.setStringProperty(org.hornetq.rest.HttpHeaderProperty.CONTENT_TYPE, "application/xml");

If the JMS producer does not set the content-type, then this information must be obtained from the REST consumer. If it is a pull consumer, then the REST client should send an Accept header with the desired media types it wants to convert the Java object into. If the REST client is a push registration, then the type attribute of the link element of the push registration should be set to the desired type.

If you have a REST client producing messages and a JMS consumer, HornetQ REST has a simple helper class for you to transform the HTTP body to a Java object. Here's some example code:

public void onMessage(Message message)
   MyType obj = org.hornetq.rest.Jms.getEntity(message, MyType.class);

The way the getEntity() method works is that if the message is an ObjectMessage, it will try to extract the desired type from it like any other JMS message. If a REST producer sent the message, then the method uses RESTEasy to convert the HTTP body to the Java object you want. See the Javadoc of this class for more helper methods.