Java comes up a lot when we talk about “real time.” Not that Java in particular has any special dibbs on the term, but frequently when a site is interested in things like Service Oriented Architecture (SOA), Web Services, messaging, and XML, they are often also interested in Java, J2EE, Application Servers and other things related to Sun’s language standard.
Integrating Java with your ETL processing becomes the next logical discussion, whether “real time” even applies. There may be some functionality, some existing algorithms worth re-using, some remote java-oriented or java managed system or message queue that contains valuable source data (or would be a valuable target), that you’d like to integrate into a data integration flow. DataStage can easily be extended to include your Java functionality or take advantage of your Java experience.
There are two Stages that used to be referred to as JavaPack that are included with DataStage: JavaClient and JavaTransformer. Both allow you to integrate the functionality of a java class into the flow of a DataStage Job. JavaClient is used for a sources or targets (only an output link or only an input link), and the JavaTransformer is used for row-by-row processing where you have something you’d like to invoke for each row that passes through.
DataStage provides a simple API for including java classes into your Jobs. This API allows your class to directly interact with the DataStage engine at run-time — to obtain meta data about the columns and links that exist in the current executing job, and to read and write rows from and to those links when called upon to do so. You define several special methods in your class, such as Process(), that the engine calls whenever it needs a row, or is giving your class control because it’s ready to give you a row. Within that method you have various calls to make, such as readRow [from an input link] and writeRow [to an output link]. You can control what comes in and goes out, and also process rejections based on logic in your class. Other than that, your class can do whatever it wants……read messages from JMS queues, invoke remote EJBs….whatever.
The JavaPack is very well documented, with examples and descriptions of all the API calls. However, I’ve included an additional example here for anyone who is interested, including java class, source, .dsx and usage notes. Have fun!
btw…I haven’t exactly figured out yet how to best get the names of the files below represented here on this blog, but if you save them from here, each file except the Readme begins with “ExamineRows” and should be ExamineRows.dsx (for the export), ExamineRows.java (for the Source) and ExamineRows.class for the actual compiled class. I haven’t had a chance to re-try it after downloading from here, so worst case, you’ll need to recompile the class yourself in your environment. Otherwise, it should run in v8 “as is”. See the file at the Readme link for details on the expected classpath in the Job, etc., and read the annotations in the Job itself after you import it. -e