11.3. API Differences Between Resources Types and Versions

One important thing to remember about the structure of objects in JBoss ON is that each resource type is defined individually, in its own plug-in descriptor. (There can be multiple resource types in a single plug-in descriptor, and these are all related as parent and children resource types.)

Each resource type has different management APIs, which reflect the software application. Obviously, a Tomcat server is different than a Postgres database, so they have different metrics, operations, and configuration properties. Even seemingly common traits like stopping and starting a resource are different depending on the resource type descriptor. Tomcat has an operation to stop gracefully (something not needed for a database or most services), while JBoss AS 5 servers are stopped and then started as separate tasks instead of restarting in one step.

An agent plug-in defines a resource type not only by the application or service, but also by the version of that application or service. An EJB resource is difference than an EJB3 resource, with a different definition.

This distinction — that different versions of the same application are treated as different resource types — is particularly critical for server resources.

Different resource types have configuration properties and operations available. This can impact CLI scripts written to manage those resources. For example, a script written for a JBoss AS 5 resource may not work for a JBoss AS 4 or JBoss AS 7 resource because the different resources have different APIs.

If you are writing a script which may be used for different versions of a server, create a CLI script which first identifies the resource type and then calls the appropriate method.