Article 2 showed how chunk processing works conceptually. This article sets up the real project you’ll build on for the rest of the series — complete Maven configuration, MySQL metadata tables, multiple ways to trigger jobs, and correct use of JobParameters. Everything in this article is production-ready from the start. Project Dependencies Add spring-boot-starter-batch to your Maven project. That one starter brings in everything you need. <?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.

Introduction Not every step in a batch job reads-processes-writes a stream of items. Sometimes you need to: Delete yesterday’s temp files before reading today’s data Truncate a staging table before loading new data Call a stored procedure to aggregate results Send an email or Slack notification after processing Execute a DDL statement to add an index These operations do not have items — they are single units of work. Spring Batch handles them with the Tasklet interface.

Introduction Spring Batch jobs are code — they need tests. Without tests you will catch errors in production. With tests you catch them in CI. Spring Batch has a dedicated testing module that provides @SpringBatchTest, JobLauncherTestUtils, and JobRepositoryTestUtils. These tools let you: Run a complete job in a test and assert on its BatchStatus Launch individual steps and inspect StepExecution counters Test readers, processors, and writers in complete isolation This article covers all three levels: unit, integration, and database integration with Testcontainers.

Introduction ItemProcessor<I, O> sits between the reader and the writer. It receives one item at a time and returns a transformed item — or null to filter the item out entirely. Processors are optional: if your job reads and writes the same type with no transformation needed, you can omit them. The processor interface is one method: public interface ItemProcessor<I, O> { O process(I item) throws Exception; } Return a processed item to pass it to the writer.

Introduction After reading and processing data, your batch job needs to write results somewhere. Spring Batch provides two essential writers: FlatFileItemWriter — writes items to CSV or any delimited/formatted flat file JdbcBatchItemWriter — writes items to a database using JDBC batch inserts/updates Both are transactional and restartable. This article covers both in depth, plus transaction semantics you must understand to avoid duplicates and partial writes. How Writers Work in Spring Batch Writers receive a Chunk<O> — a list of all items processed in the current transaction.