Book Image

Talend Open Studio Cookbook

By : Rick Barton
Book Image

Talend Open Studio Cookbook

By: Rick Barton

Overview of this book

Data integration is a key component of an organization's technical strategy, yet historically the tools have been very expensive. Talend Open Studio is the world's leading open source data integration product and has played a huge part in making open source data integration a popular choice for businesses worldwide.This book is a welcome addition to the small but growing library of Talend Open Studio resources. From working with schemas to creating and validating test data, to scheduling your Talend code, you will get acquainted with the various Talend database handling techniques. Each recipe is designed to provide the key learning point in a short, simple and effective manner.This comprehensive guide provides practical exercises that cover all areas of the Talend development lifecycle including development, testing, debugging and deployment. The book delivers design patterns, hints, tips, and advice in a series of short and focused exercises that can be approached as a reference for more seasoned developers or as a series of useful learning tutorials for the beginner.The book covers the basics in terms of schema usage and mappings, along with dedicated sections that will allow you to get more from tMap, files, databases and XML. Geared towards the whole lifecycle, the Talend Open Studio Cookbook shows readers great ways to handle everyday tasks, and provides an insight into all areas of a development cycle including coding, testing, and debugging of code to provide start-to-finish coverage of the product.
Table of Contents (21 chapters)
Talend Open Studio Cookbook
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Common Type Conversions
Index

Printing tMap variables


If you inspect code generated from a tMap variable, you will see that each of the expressions are converted into a line of the following format:output column = expression;.

This suggests that the expression is limited to one line of Java code.

Although this is how we would normally treat tMap expressions (in order to avoid confusion), this isn't strictly true, and there is one scenario where breaking this rule may be useful.

The scenario in question relates to tMap variables. If a tMap variable fails due to an exception in a variable expression that is itself a result of a variable expression, then the job can become quite difficult to debug.

To make it easier to see what is happening in each step, we can add a System.out.println code to an expression to print the state prior to execution of the failing step.

In this case, we simply force the expression logic in the generated code to become: output column = expression; System.out.println(output column);

This is how it looks...