I started the server using domain.bat.
Below the steps i have performed:
1. downloaded the jboss-as-7.2.0.Alpha1-SNAPSHOT
2. started the server using domain.bat
3. I can see the datasource(java:jboss/datasources/ExampleDS) in the admin console under 'Datasources' section.
4. I deployed my simple web application(you can find it attached) via the admin console, the application has a servlet and has the logic to lookup the datasource in the init method.
Eventhough the datasource is shown in the admin console, the lookup is failing inside the servlet.
But when i deploy the same web application in jboss-as-7.1.1.Final , it works.