Read Environment Variables in persistence.xml file

Question

I want to read environment variables inside persistence.xml file.

Idea is that i don\'t want my database details to be read from properties file as

Answer 1

You can update properties in a persistence unit by supplying a Map (see this).

Conveniently, environment variables can be retrieved as a Map (see this).

Put the two together and you can dynamically update properties in your persistence unit with environment variables.

EDIT: simple example...

persistence.xml...

    
        oracle.toplink.essentials.PersistenceProvider
    
    false
    
        
        
        
        
        
    

code that updates persistence.xml "default" unit with environment variables...

Map env = System.getenv();
Map configOverrides = new HashMap();
for (String envName : env.keySet()) {
    if (envName.contains("DB_USER")) {
        configOverrides.put("toplink.jdbc.user", env.get(envName)));    
    }
    // You can put more code in here to populate configOverrides...
}

EntityManagerFactory emf =
    Persistence.createEntityManagerFactory("default", configOverrides);