Dealing with the Data Types

After jCOM is configured and up and running, you'll find that the only real day-to-day programming task you'll encounter is in dealing with the data types that you send and receive from the server objects you've exposed. From a Java or COM client perspective, you'll need to reconcile between individual idiosyncrasies in the primitive data type mappings that jCOM provides.

Overall, jCOM should be given credit for providing a workable solution to a difficult problem and doing a very good job of mapping primitive and complex data types across platforms into a form familiar to programmers on either side. But as with all integration efforts, you shouldn't expect perfection. For example, a COM VariantEnumeration type is mapped to a java.lang.Enumeration in Java. COM enumerations have no equivalent to the hasMoreElements() method, so you'll have to work around this by using the nextElement method until you get a NoSuchElementException.

As an alternative, under the Server/ServerName/Connections/jCOM tab on the WebLogic Server Console, you can check Prefetch Enums. In the background, jCOM will pre-fetch the next element so that hasMoreElements() will work correctly.

See Table 33.2 for a sample of how types are mapped between COM and Java. I refer you to the J-Integra Web site documentation where you will find very useful detailed listings of all the latest type mappings: http://www.intrinsyc.com/support/j-integra/doc/. In Contents, look under Reference/Type Mapping.