<persistence-unit ... transaction-type="RESOURCE_LOCAL">
      <non-jta-data-source>java:/MyDatasource</non-jta-data-source>
      <properties>
            <property name="hibernate.transaction.factory_class" value="org.hibernate.transaction.JDBCTransactionFactory"/>
            ...

            InitialContext jndiCtx = new InitialContext( props );
            ComboPooledDataSource datasource = new ComboPooledDataSource(); // C3P0
            datasource.setDriverClass("org.hsqldb.jdbcDriver");
            datasource.setJdbcUrl("jdbc:hsqldb:hsql://localhost");
            datasource.setUser("sa");
            datasource.setPassword("");
            datasource.setMaxPoolSize(20);
   
            jndiCtx.bind("java:/MyDatasource", datasource);

   String dbDriver = "org.postgresql.Driver";
      String dbUrl = "jdbc:postgresql://localhost/dbname";
      String dbUser = "postgres";
      String dbPassword = "postgres";
      String dbDialect = "org.hibernate.dialect.PostgreSQLDialect";

      HashMap<String, String> props = new HashMap<String, String>();
      props.put("hibernate.connection.driver_class", dbDriver);
      props.put("hibernate.connection.url", dbUrl);
      props.put("hibernate.connection.username", dbUser);
      props.put("hibernate.connection.password", dbPassword);
      props.put("hibernate.dialect", dbDialect);
      props.put("hibernate.show_sql", "true");

      try
      {   
         emf = Persistence.createEntityManagerFactory("puname",props);
         em = emf.createEntityManager();
      }

<persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd" version="1.0">
   <persistence-unit name="puname" transaction-type="RESOURCE_LOCAL">
   </persistence-unit>
</persistence>