Posts Tagged ‘ResourceAdapter

24
Dec
08

Inbound JCA Connectors Introduction

After some posts about Outbound JCA connectors, let’s have a look at the concepts related to an Inbound JCA connector.

First question I always hear: “So, the server (legacy application) connects a client socket into a server socket on my J2EE server, right?” and I always answer: “depends”. People tends to think that the term inbound and outbound are related to TCP/IP connection, but, in fact, it is related to the flow of the process. In an outbound connector, our system is the actor and if you trace the flow of the call you’ll notice that it is leaving from our system to the legacy one; or perharps we could say outgoing. On the other hand, in an inbound connector, the actor is the legacy system that is triggering an ingoing message that is started outside our system and goes all the way into it.

Let’s see a sequence diagram of an inbound connector to make things clearer:

JCA Inbound Connector Sequence Diagram

JCA Inbound Connector Sequence Diagram

As you can see in the diagram, the component that ties the Application Server, the legacy system and the J2EE Application is the ActivationSpec.

Usually, instance configurations such as port, host and other instance related data is stored on the ActivationSpec, you may also have configuration in the ResourceAdapter itself, but remember that all the configurations placed on the ResourceAdapter will be shared across multiple ActivationSpecs that may be deployed on this ResourceAdapter.

The real class responsible for handling Enterprise Events is ResourceAdapter dependant and will be initialized during endpointActivation method call on a ResourceAdapter. These classes are usually implemented as a Thread or they implement the Work interface and are submitted to the container for execution through the WorkManager instance. If you opt to use a simple Thread, remember to daemonize it otherwise your application server wont be able to properly shutdown.

For the next weeks I’ll be posting some insights about how to implement an Inbound Connector using JCA.

01
Sep
08

Outbound JCA connectors introduction

Continuing with the posts about JCA I’ll start with the project of an Outbound JCA Connector that I’ll call FooJCA. First of all and let make this clear, I am not stating that this design is an optimal JCA Connector design, what I can say is that I tried to make as compliant as possible from my understanding of the documentation.

Lets start with a overall view of the main classes and interfaces involved in a JCA Connector implementation.

Foo Connector Class Diagram

Foo Connector Class Diagram

First class to take note, the FooResourceAdapter, that’s one of the connector classes that is able to directly communicate with the container and use some priviledged services (eg.: scheduling Work instances or creating timers). This ability is provided by the BootstrapContext that is passed as a parameter of the start method by the container.

Another key class that also has the ability of interacting with the container is the FooManagedConnectionFactory. As you may have already noticed, this class isn’t always container dependant, or at least it may not be (that’s up to the developer the choice of providing functionality of the Connector outside the container). The difference (between working inside the container or outside it) is usually detected when the class method createConnectionFactory is called with or without the ConnectionManager. Talking about the ConnectionManager this is a Container implemented class that is responsible for pooling connections and related work. This Container work relies on the matchManagedConnections method that is provided by the ManagedConnectionFactory, so, pay much attention to this method implementation.

Moving on, the FooConnectionRequestInfo is a implementation of the ConnectionRequestInfo interface and is the class responsible for passing Connector dependant details about the request between the Container and the JCA Connector. One of the requisites of this class is that it implements equals and hashCode.

The FooManagedConnectionFactory as you may guess is the class responsible for creating the FooConnectionFactory instances and FooManagedConnection instances as well. It does not matter if the FooConnectionFactoryImpl instance will be Container dependent or not, it will be FooManagedConnectionFactory’s role of creating it.

At least but not last, the FooConnectionFactoryImpl will be the class responsible for creating FooConnectionImpl instances when requested (this will be treated in a separate post since it is a little long topic).

And, for finishing this post, FooManagedConnectionImpl is the class responsible for wrapping a FooConnectionImpl and returning delegates (FooConnectionHandle class) that implement FooConnection interface and notifies the container about the status of the ManagedConnection connection.

That’s enough for this post, keep on watching the blog for the rest of the implementation of the Outbound JCA Connector.




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