Where did that come from? Java EE 6 Web Profile JAR listing

As part of our new SAP Gateway Consumption Service upgrade, I have been working on updates and migration of the Gateway Registration server.

The improvements are all “behind the scenes”, so you as a user won’t notice them.  The changes, however, reminded me to post a few things I’ve learned about working with Java and HANA Cloud Platform.

One of my biggest challenges is determining what classes to use.  Our current system runs in the “Java EE 6 Web Profile”, which uses the older Java 7 virtual machine.  It’s based on the (now old) Java EE 6 specification, as you can see from the supported standards web page.  The documentaton also provides a list of the packages that come included.

To figure this out, I decided to do some digging in to the underlying structure in HCP.  The classloaders for all the custom classes in the project are, of course, separate from the rest of the core classes.  It’s pretty simple to work around this.  Starting with a known “core” class (javax.servlet.Servlet), I had the classloader print itself out.  It quickly admits that Servlet is loaded from file:/usr/sap/ljs/plugins/javax.servlet_3.0.0.v201103241009.jar.  From there, it’s just a matter of asking a File object to list out the entire directory.

This is a list of the core libraries that come with HCP.  All of these JAR files also comes with a version, so you can quickly determine which one to load should you need to access it.

Finally, if you do load any of these classes in your editor, be sure to tell Maven they are “provided” classes, so they won’t be loaded in the WAR file.  You won’t need them, and they will just take up space.

I hope this helps!