The Glassfish application server has a problem with JNDI names for datasources in the following form:

java:/xyz

... and prefers datasources to have JNDI names like this:

jdbc/xyz

For instance, instead of:

  
      jdbc:postgresql://127.0.0.1:5432/orders
      org.postgresql.Driver
                (...)

... use the following:

  
      jdbc:postgresql://127.0.0.1:5432/orders
      org.postgresql.Driver
                (...)