Guiced Persistence allows you to configure your configurations in any way, programmatically deciding what to use based on any means you deem necessary

The following services providers are available 
IPropertiesConnectionInfoReader - A functional interface to populate a connection base info based on properties received
IPropertiesEntityManagerReader - Manages properties passed into the entity manager factory
ITransactionHandler - A service for managing Entity Manager Transactions automagic like

These allow to manipulate the ConnectionBaseInfo specified by each DatabaseModule accordingly. The following services are provided by default and each provide properties that you can manipulate (or use persistence.xml file properties) 
ITransactionHandler - BTMAutomatedTransactionHandler, JPAAutomatedTransactionHandler
IPropertiesEntityManagerReader - SystemEnvironmentVariablesPropertiesReader, HibernateEntityManagerProperties, BTMConnectionProperties
IPropertiesConnectionInfoReader - JPADefaultConnectionBaseBuilder, HibernateDefaultConnectionBaseBuilder

Each of the handlers perform a specific function in order to correctly load a persistence unit 
BTMAutomatedTransactionHandler - Handles transaction start and stops for JTA (EntityAssist)
JPAAutomatedTransactionHandler - Manages transactions start and stops for JTA (EntityAssist)

BTMConnectionProperties - Applies the default persistence.xml properties to connect to BTM for transaction management
HibernateEntityManagerProperties - Assigns programmatic changes to persistence.xml for hibernate specific properties
SystemEnvironmentVariablesPropertiesReader - Allows setting persistence.xml properties based on system environment variables ${os.name}

JPADefaultConnectionBaseBuilder - Reads persistence.xml persistence properties and sets the ConnectionBaseInfo accordingly
HibernateDefaultConnectionBaseBuilder - Reads persistence.xml hibernate properties and sets the ConnectionBaseInfo accordingly
Every aspect of the connection (should) be modifyable allowing straight forward access to testing your entities and classes

Additional examples modules are available to see how to map from other sources,
  • Wildfly Connection Properties
    • - Reads standalone files for connection information
    - Use WildflyConnectionInfoBuilder.setStandaloneFileName("standalone-full-ha.xml"); to set which file to read from
    - Set the ${jboss.server.config.dir} accordingly
    - You can create services for IWildflyDriverRegistration to register any custom drivers whose properties are unable to read
    - By default SQL Server and DB2 drivers are made available and provide good examples of registering your own
  • C3P0 Properties
    • - Dynamically set C3P0 pool properties within your code