Spring Batch 3 Part Series

Using Spring 6.2.3 & Spring Batch 5.2.2 (Java 21+)

This project demonstrates three common Spring Batch patterns using XML configuration and an embedded HSQLDB database.

Prerequisites

• Java 21 or higher
• Maven 3.8+

Getting Started

# Clone the repository
git clone <repository-url>
cd springbatch3part

# Build the project
mvn clean compile

# Run all tests (executes all three batch jobs)
mvn test

Project Structure

src/main/java/com/batch/
├── AppJobExecutionListener.java   # Job lifecycle listener with MDC and duration
├── BatchMetricsLogger.java        # Micrometer metrics recording and summary
├── ItemFailureLoggerListener.java # Error handling listener
├── StepMetricsListener.java       # Step metrics with timing and commit counts
├── simpletask/
│   ├── HelloTask.java             # Prints a greeting message
│   └── TimeTask.java              # Prints the current time
├── todb/
│   ├── Ledger.java                # Domain record (Java record)
│   ├── LedgerMapper.java          # Maps flat file fields to Ledger
│   └── LedgerProcessor.java       # Validates and normalizes Ledger records
└── fromdb/
    └── LedgerRowMapper.java       # Maps DB rows to Ledger

src/test/java/com/batch/
├── AppTest.java                   # Ledger record unit tests
├── simpletask/
│   └── SimpleTaskletTestCase.java # Runs the simple tasklet job
├── todb/
│   ├── LedgerMapperTest.java      # Unit tests for CSV field mapping
│   └── ToDBBatchTestCase.java     # Integration test: flat-file-to-DB job
└── fromdb/
    ├── LedgerRowMapperTest.java   # Unit tests for DB row mapping
    └── FromDBBatchTestCase.java   # Integration test: DB-to-flat-file job

The Three Batch Jobs

Part I - Simple Tasklet

A two-step job that prints a greeting message followed by the current time.

mvn test -Dtest=SimpleTaskletTestCase

Part II - Flat File to Database

Reads ledger records from a CSV file (src/main/resources/ledger.txt), validates and normalizes them through an ItemProcessor, and writes them to an HSQLDB table using JdbcBatchItemWriter. Includes skip/retry fault tolerance policies.

mvn test -Dtest=ToDBBatchTestCase

Part III - Database to Flat File

Reads ledger records from the database and writes them to a CSV file (target/ledgers-output.txt).

mvn test -Dtest=FromDBBatchTestCase

Observability

All three batch jobs are instrumented with listeners that provide:

• MDC Context — Every log line includes job and step names for correlation (e.g., [job=simpleJob step=step1])
• Job Duration — Start time, end time, and total duration logged at job completion; failures logged at ERROR level with exception details
• Step Metrics — Read, processed, written, skipped, filtered, commit, and rollback counts with step duration
• Micrometer Metrics — Job timers (batch.job.duration), counters (batch.job.count), and step-level gauges/counters recorded via SimpleMeterRegistry with a summary logged after each job
• Error Logging — Read and write errors captured by ItemFailureLoggerListener
• Persistent Logs — Rolling file appender writes to logs/batch.log with 30-day retention

Technology Stack

Component	Version
Java	17+
Spring Framework	6.2.3
Spring Batch	5.2.2
Micrometer	1.14.4
JUnit	5.11.4
HSQLDB	2.7.4
SLF4J + Logback	2.0.16 / 1.5.16

Modernization Journey

This project was originally written in 2013 using Java 1.5, Spring 3.1, and Spring Batch 2.1. It has been fully modernized to current standards. Here is a summary of every change made during the upgrade.

Platform Upgrade

Component	Before (2013)	After
Java	1.5	21
Spring Framework	3.1	6.2.3
Spring Batch	2.1	5.2.2
JUnit	3.x	5.11.4 (Jupiter)
HSQLDB	1.8	2.7.4
Logging	commons-logging	SLF4J 2.0 + Logback 1.5
Build	Maven (Java 1.5)	Maven (Java 21)

Java Language Modernization

• Java record — Replaced mutable Ledger JavaBean (getters/setters/constructor) with an immutable record
• java.time — Replaced java.util.Date and Calendar with LocalDate and LocalDateTime throughout
• BigDecimal — Replaced double with BigDecimal for all monetary fields (depositAmount, paymentAmount)
• var — Used local variable type inference where it improves readability
• Parameterized logging — Replaced string concatenation ("Job: " + id) with SLF4J placeholders ("Job: {}", id)
• Removed throws Exception — Cleaned up unnecessary checked exception declarations on tasklet methods
• Meaningful parameter names — Renamed arg0, arg1 to contribution, chunkContext in tasklet methods
• Extracted helper method — Deduplicated dollar-parsing code in LedgerMapper into parseDollarAmount()
• Enhanced switch — Replaced if/else chain on BatchStatus with pattern matching switch expression (Java 21)
• Wildcard cleanup — Changed Chunk<? extends Object> to Chunk<?> in listener signatures

Spring Batch Framework Improvements

• Eliminated custom DAO layer — Removed LedgerDAO, LedgerDAOImpl, and LedgerWriter (3 files). Replaced with Spring Batch's built-in JdbcBatchItemWriter with BeanPropertyItemSqlParameterSourceProvider, reducing boilerplate
• Added ItemProcessor — New LedgerProcessor validates records (filters negative amounts) and normalizes data (uppercases paymentType), implementing the full Reader-Processor-Writer pipeline
• Fault tolerance — Added skip policy for FlatFileParseException (skip-limit=10) and retry policy for DeadlockLoserDataAccessException (retry-limit=3) to the chunk configuration
• @SpringBatchTest — Migrated all integration tests to use JobLauncherTestUtils with proper job execution assertions
• Shared base context — Extracted duplicated XML infrastructure (DataSource, TransactionManager, JdbcTemplate, JobRepository, JobLauncher) into base-batch-context.xml, imported by all three job contexts
• DECIMAL column type — Changed the ledger table DDL from double to DECIMAL(12,2) for monetary columns

Test Suite Expansion

The original project had 1 trivial test (assertTrue(true)). The modernized project has 14 tests:

• AppTest — 4 unit tests for Ledger record construction and BigDecimal field precision
• LedgerMapperTest — 4 unit tests for CSV field mapping and dollar amount parsing
• LedgerRowMapperTest — 3 unit tests for database row mapping with mock ResultSet
• SimpleTaskletTestCase — Integration test verifying the two-step tasklet job completes
• ToDBBatchTestCase — Integration test verifying flat-file-to-DB job with item count assertions
• FromDBBatchTestCase — Integration test verifying DB-to-flat-file job with output verification

Observability

• MDC context propagation — Job name and step name added to every log line via SLF4J MDC
• Job duration and error reporting — Enhanced AppJobExecutionListener with timing, exit descriptions, and ERROR-level failure logging with exception details
• Step metrics — Enhanced StepMetricsListener with step duration, commit count, and rollback count
• Micrometer integration — Added BatchMetricsLogger with SimpleMeterRegistry recording job timers, counters, and step-level gauges
• Structured log pattern — Updated Logback to include MDC fields: [job=%X{jobName} step=%X{stepName}]
• Persistent logging — Added rolling file appender (logs/batch.log) with 30-day retention
• Full listener coverage — All three jobs now have job-level and step-level listeners (FromDB job previously had none)

Test Isolation Fixes

• DROP TABLE IF EXISTS — Added schema-drop-ddl.sql to prevent "object already exists" errors when @SpringBatchTest reuses Spring contexts with in-memory HSQLDB
• @BeforeEach cleanup — Added table cleanup in tests to prevent row count mismatches from shared in-memory databases

Original Blog Series (from 2013)

• Part I - Simple Tasklet: http://blogs.justenougharchitecture.com/?p=124
• Part II - Flat File To Database: http://blogs.justenougharchitecture.com/?p=122
• Part III - From Database to Flat File: http://blogs.justenougharchitecture.com/?p=118