datasource vs hard coded

persistance-bad.xml

<persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="2.2"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_2.xsd">
    <persistence-unit name="my-persistence-unit">
        <properties>
            <!-- database connection -->
            <property name="javax.persistence.jdbc.driver" value="org.postgresql.Driver" />
            <property name="javax.persistence.jdbc.url" value="jdbc:postgresql://localhost:5432/jpaForBeginners" />
            <property name="javax.persistence.jdbc.user" value="postgres" />
            <property name="javax.persistence.jdbc.password" value="postgres" />
        </properties>
    </persistence-unit>
</persistence>

persistance.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.2"
             xmlns="http://xmlns.jcp.org/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_2.xsd">
  <persistence-unit name="prod">
    <jta-data-source>java:jboss/datasources/ExampleDS</jta-data-source>
    <properties>
      <property name="hibernate.show_sql" value="true" />
      <property name="hibernate.format_sql" value="true"/>
      <property name="hibernate.hbm2ddl.auto" value="create" />
    </properties>
  </persistence-unit>

</persistence>