concept business logic in category spring
This is an excerpt from Manning's book Spring Batch in Action.
That’s it—you’ve implemented a full-blown job with Spring Batch! This shows how Spring Batch provides a powerful framework to create batch jobs and handles the heavy lifting like file I/O. Your main tasks were to write a couple of Java classes and do some XML configuration. That’s the philosophy: focus on the business logic and Spring Batch handles the rest.
Figure 6.4. The interfaces and classes involved in writing items to a flat file with the FlatFileItemReader. The FlatFileItemWriter also provides optional callbacks for the header and the footer of a flat file. The LineAggregator transforms an item into a string. The ExtractorLineAggregator implementation uses a FieldExtractor to ���split��� an item into an array of objects and calls business logic to render the array as a string.
Chapters 5 and 6 focused heavily on Spring Batch input and output: how to read and write data from various types of data stores. You learned that Spring Batch enforces best practices to optimize I/O and provides many ready-to-use components. This is important for batch applications because exchanging data between systems is common. Batch applications aren’t limited to I/O; they also have business logic to carry on: enforcing business rules before sending items to a database, transforming data from a source representation to one expected by a target data store, and so on.
In Spring Batch applications, you embed this business logic in the processing phase: after you read an item but before you write it. Thanks to its chunk-oriented architecture, Spring Batch provides first-class support for this type of processing in a dedicated component—the item processor—that you insert between the item reader and the item writer. After explaining item processing and its configuration in Spring Batch, we show you how to use item processors to modify, filter, and validate items. For validation, we examine two techniques: programmatic validation in Java and validation through configuration files using a validation language and validation annotations. Finally, we cover how to chain item processors following the composite design pattern. By the end of this chapter, you’ll know exactly where and how to write the business logic for your batch application. You’ll also learn about advanced topics, such as the distinction between filtering and skipping items. Let’s start with processing items in Spring Batch.