Jun Qian (钱骏) 's Weblog

Anatomy of Composite Application in NetBeans 6.0 SOA Pack (Part 4)

Connection Auto-Generation

A composite application is composed of multiple component projects. At composite application build time, the project system automatically generates connections based on the interfaces of the endpoints defined in the component projects. There are three types of endpoints from which the composite application project system tries to make connections:

• the Consume endpoints defined in the component projects' service unit descriptors (jbi.xml);
• the Provide endpoints defined in the component projects' service unit descriptors (jbi.xml);
• the WSDL Ports defined in WSDL files in the component projects and in the composite application project.
  

You already know that an endpoint is uniquely identified by its fully qualified endpoint name. This name has nothing to do with whether two endpoints are connectable or not. The endpoint connectability depends on the interface of the endpoint. The endpoint interface name is actually a QName. If a Consume endpoint and a Provide endpoint have the same interface QName, they are connectable. The same is true for a Consume endpoint and a WSDL Port pair, or a Provide endpoint and a WSDL Port pair.
 
The following image shows a BPEL SU's jbi.xml, XSLT SU's jbi.xml and a (partial) WSDL file defined in the BPEL Module. It also shows how the connections are created based on the endpoints/ports' interfaces. Note the highlighted matching interface/portType name.

The following shows what you get (in CASA Editor) after this composite application gets built:

Note that for endpoints with identical interface QName, it's perfectly fine to connect multiple Consume endpoints to one Provide endpoint. However, it's not OK for one Consume endpoint to connect to more than one Provide endpoint. Neither the Composite Application Project System nor the CASA Editor allows this to happen. Think about it. If a Consumer is allowed to connect to multiple Providers at design time, which Provider will actually provide the service at runtime?

At build time, if there are multiple Provide endpoints matching the same Consume endpoint, since the project system does not know which Provide endpoint is the desired one, no connection will be generated. The project system simply displays a warning message in this case and the decision is left to the user. The user can use the CASA Editor to choose the preferred Provide endpoint and make the desired connection.

Posted at 01:28AM May 04, 2007 by Jun Qian in NetBeans  |  Comments[2]