Question:

Similar to <a href="https://stackoverflow.com/questions/4051273/what-to-put-into-jta-data-source-of-persistence-xml" rel="nofollow">What to put into jta-data-source of persistence.xml?</a> and <a href="https://stackoverflow.com/questions/42434282/how-to-map-jpa-datasources-in-wildfly" rel="nofollow">How to map jpa datasources in WildFly?</a>

However, I am asking for something that would work on all vendors or at least WildFly, Glassfish/Payara, WebSphere Application Server classic, WebSphere Application Server Liberty, TomEE. I am not looking for something that works in a Java SE Unit test.

So far I found that java:comp/env/jdbc/xxx works in WebSphere Application Server and TomEE. There's a mapping exercise (which is expected) to get it working but I cannot get the same to work on GlassFish/Payara and JBoss/WildFly.

More specifically I do not wish to use default data source because for my scenario I am actually working on two different data sources. E.g. for reference data and another for transactional.

If all of the app servers you work with are Java EE 7 compliant, you can use the default data source, which is required per EE7 spec to be available at:

java:comp/DefaultDataSource

The app server you run on ought to let you customize the configuration of the DefaultDataSource.

Since I'm familiar with WebSphere Liberty, I can point you to this doc for default data sources on Liberty:<br /><a href="https://www.ibm.com/support/knowledgecenter/SSAW57_liberty/com.ibm.websphere.wlp.zseries.doc/ae/twlp_config_dds.html" rel="nofollow">Configuring a default data source</a>

If you are using WebSphere traditional, as of v9.0 it supports Java EE 7, and has a default data source available out of the box (under the spec mandated JNDI name).

If you want to use the same JNDI name that works on all servers, it's best to use resource references, as explained in <a href="https://stackoverflow.com/questions/2887967/what-is-resource-ref-in-web-xml-used-for" rel="nofollow">What is resource-ref in web.xml used for?</a>

Basically, you would define an arbitrary JNDI name (ideally without any java:comp prefix or similar, just something like "myDatasource") and then map it to the concrete JNDI name provided by the target server.You would need to define a server-specific descriptor for each server with the mapping the if the server cannot use the JNDI directly (e.g. glassfish-web.xml for GlassFish/Payara, jboss-web.xml for WildFly, ibm-web-bnd.xml for WebSphere Classic and Liberty). TomEE seems to support references without any prefix, so it should be able to <a href="https://tomee.apache.org/configuring-datasources.html" rel="nofollow">configure a datasource</a> without any additional mapping if you choose a name without a prefix.