I am fairly new to JPA and in my project the applciation server is Glassfish 3.1.2 .So when i encountered persitence.xml in my project ,I have gone through http://en.wikibooks.org/wiki/Java_Persistence/Runtime to get basic idea of how it is used in JavaSE and JavaEE. However i came across few properties that are configured via ${}.
<jta-data-source>${dataSource}</jta-data-source>
<property name="javax.persistence.jdbc.user" value="${testDBUser}" />
So i am confused where these variables (dataSource,testDBUser..etc) are defined. And so i have gone through this http://tomee.apache.org/configuring-persistenceunits-in-tests.html and http://forcedotcom.github.io/java-sdk/connection-url. I understood that these are either system varibales and environmental variables / initial context variables.
However i do not know where they are configured/declared ,i searched my entire project for these variables but of no luck.
Are these variables are configured during the start-up of the application server / are they declared in any *.xml of the application server.
Can you please brief where these are declared?