Applying Scope for JDBC Resources in GlassFish

JDBC Resources With Scope in GlassFish

Applying Scope for JDBC Resources in GlassFish

Java EE 6 introduces new set of application component environment namespace scopes.
Using the scope, an application can define (or export) a name such that it is visible for other components or modules within the application or even visible globally.

Scope:

  • java:comp : per component namespace
  • java:module : namespace shared by all components in a module (eg: ejb's in a ejb-jar.xml)
  • java:app : namespace shared by all components, modules in an application (eg: application-client, web component, ejb component in an application, .ear)
  • java:global : global namespace for all applications in the server

It is possible to define names with scope and thus make it available across the module, application or globally.

eg:
  • <res-ref-name> element's "name" attribute with prefixed value "java:comp/env/" will make the resource available only for the component in which it is defined (eg: Servlet or EJB or Application Client)
  • <res-ref-name> element's "name" attribute with prefixed value "java:module/env/" will make the resource available all the ejb components defined in its ejb-jar.xml (All EJBs in an ejb-jar.xml)
  • <res-ref-name> element's "name" attribute with prefixed value "java:app/env/" will make the resource available across all components/modules in the application (EJBs, Servlet, Application Client in the application)
  • <res-ref-name> element's "name" attribute with prefixed value "java:global" will  make the resource available across the server

By default, if no prefix is specified it will be equivalent to "java:comp"

Demo application :

The sample application provided demonstrates the usage of various scopes across the application,  by specifying resource-ref in deployment-descriptors. The sample has following components
  • web component [Servlet.java]
  • ejb component(s) [HelloStatefulEJB.java and HelloEJB.java]
  • application client [Client.java]
When executed for a particular resource name, the sample application will do lookup of the resource in Application Client, EJB(s), Servlet and based on the availability
of the resource in the component's scope it will either use the provided resource (datasource) or the default jdbc-resource (jdbc/__default).

Following are the resources defined (or exported) by the application.
  • java:global/env/Servlet_Resource
  • java:app/env/HelloStatefulEJB_Resource
  • java:module/env/HelloEJB_Resource
  • java:comp/env/Appclient_Resource

From the name, the scope of the resource, component in which the resource is defined can be identified.
In the following example :java:app/env/HelloStatefulEJB_Resource
Scope is "app"
Resource is defined for "HelloStatefulEJB"



Steps to execute:

  1. Ensure that JDK 1.6 is installed and the environment variable JAVA_HOME is set
    1. Ensure that the environment variable PATH has JAVA_HOME/bin added to it.
  2. Ensure that ANT is installed and the environment variable ANT_HOME is set
    1. Ensure that the environment variable PATH has ANT_HOME/bin added to it.
  3. Download GlassFish v3
  4. Install GlassFish v3
  5. Start GlassFish (asadmin start-domain domain1)
  6. Start Derby database (asadmin start-database)
  7. Download the sample
  8. Extracted location of sample is referred as "SAMPLE_HOME"
  9. goto SAMPLE_HOME
  10. set environment variable GF_HOME to GlassFish's installation location.
  11. "ant all" will compile, assemble, deploy, run the application and then undeploy the application.


Sample Output :

Existing build.xml is configured to demostrate the availability of the following resources across Application Client, Servlet, EJB(s)

  • java:global/env/Servlet_Resource
  • java:app/env/HelloStatefulEJB_Resource
  • java:module/env/HelloEJB_Resource
  • java:comp/env/Appclient_Resource


Sample output for
"java:module/env/HelloEJB_Resource" will look like :

     [exec] Mode : appclient
     [exec] Resource name : java:module/env/HelloEJB_Resource
     [exec] ----------------------------------------------------------------------------------------------------------
     [exec] REQUESTED RESOURCE              : java:module/env/HelloEJB_Resource
     [exec] ACTUAL RESOURCE USED          : jdbc/__default
     [exec] RESULT                                        : RESOURCE NOT ACCESSIBLE
     [exec] ----------------------------------------------------------------------------------------------------------
     [exec]
     [exec]
     [exec] Mode : servlet
     [exec] Resource name : java:module/env/HelloEJB_Resource
     [exec] ----------------------------------------------------------------------------------------------------------
     [exec] REQUESTED RESOURCE              : java:module/env/HelloEJB_Resource
     [exec] ACTUAL RESOURCE USED          : jdbc/__default
     [exec] RESULT                                        : RESOURCE NOT ACCESSIBLE
     [exec] ----------------------------------------------------------------------------------------------------------
     [exec]
     [exec]
     [exec] Mode : stateful_ejb
     [exec] Resource name : java:module/env/HelloEJB_Resource
     [exec] ----------------------------------------------------------------------------------------------------------
     [exec] REQUESTED RESOURCE              : java:module/env/HelloEJB_Resource
     [exec] ACTUAL RESOURCE USED          : java:module/env/HelloEJB_Resource
     [exec] RESULT                                        : RESOURCE ACCESSIBLE
     [exec] ----------------------------------------------------------------------------------------------------------
     [exec]
     [exec]
     [exec] Mode : stateless_ejb
     [exec] Resource name : java:module/env/HelloEJB_Resource
     [exec] ----------------------------------------------------------------------------------------------------------
     [exec] REQUESTED RESOURCE              : java:module/env/HelloEJB_Resource
     [exec] ACTUAL RESOURCE USED          : java:module/env/HelloEJB_Resource
     [exec] RESULT                                        : RESOURCE ACCESSIBLE
     [exec] ----------------------------------------------------------------------------------------------------------



In the above sample, "RESULT" indicate that the datasource "java:module/env/HelloEJB_Resource" is available only for the EJB components in the ejb-jar.xml ie., HelloEJB and HelloStatefulEJB.


References :



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