title: Read Environment Variables in persistence.xml file
body: <p><strong>I want to read environment variables inside persistence.xml file.</strong></p>
  
  <p>Idea is that i don't want my database details to be read from properties file as there is a change of getting properties file override.Instead i want to read details from environment variables.</p>
  
  <p>Is there any way to achieve this criteria.</p>
  
  <p>Iam using Spring 3 my standalone application will be deployed in unix machine.</p>