Overview

    Create a simple Hello World output batch program by combining Spring Batch Tasklet and Spring Boot

Evironment

• Spring Batch 4.3.1 + Spring Boot 2.4.2
• Java 11 (AdoptOpenJDK 11.0.10+9)
• Gradle 6.8.1
• macOS Catalina

Spring Batch execution configuration

• Job calls multiple Steps
• Step calls Tasklet

What is job

    Spring Batch batch domain language-reference

    In Spring Batch, Job is just a container for Step instances. It combines multiple steps that logically belong together in a flow, allowing you to configure global properties for all steps, such as restartability.

What is step

    Spring Batch batch domain language-reference Step is a domain object that encapsulates the independent sequential phases of a batch job. Every job is fully configured in one or more steps. The Step contains all the information you need to define and control the actual batch processing.

What is Tasklet

    Spring Batch batch domain language-reference Tasklet is a simple interface with one method called execute. execute is called repeatedly by TaskletStep until it returns RepeatStatus.FINISHED or throws an exception to signal a failure.

Source code

File list

├── build.gradle
└── src
    └── main
        └── java
            └── com
                └── example
                    └── hello
                        ├── HelloApplication.java
                        ├── HelloConfig.java
                        └── MessageTasklet.java

build.gradle

plugins {
  id 'org.springframework.boot' version '2.4.2'
  id 'io.spring.dependency-management' version '1.0.11.RELEASE'
  id 'java'
}

group = 'com.example'
version = '0.0.1'
sourceCompatibility = '11'

repositories {
  mavenCentral()
}

dependencies {
  // Spring Batch
  implementation 'org.springframework.boot:spring-boot-starter-batch'

  // DB that will be inserted metadata of Spring Batch
  implementation 'com.h2database:h2:1.4.200'

  // Lombok
  compileOnly 'org.projectlombok:lombok:1.18.18'
  annotationProcessor 'org.projectlombok:lombok:1.18.18'
}

src/main/java/com/example/hello/HelloApplication.java

package com.example.hello;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

// Spring Boot Application class
@SpringBootApplication
public class HelloApplication {

  public static void main(String[] args) {
    SpringApplication.run(HelloApplication.class, args);
  }
}

src/main/java/com/example/hello/HelloConfig.java

package com.example.hello;

import lombok.RequiredArgsConstructor;
import org.springframework.batch.core.Job;
import org.springframework.batch.core.Step;
import org.springframework.batch.core.configuration.annotation.EnableBatchProcessing;
import org.springframework.batch.core.configuration.annotation.JobBuilderFactory;
import org.springframework.batch.core.configuration.annotation.StepBuilderFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

// Batch configuration class
@Configuration // Annotation indicating that it is a Bean definition class
@EnableBatchProcessing // Enable Spring Batch
@RequiredArgsConstructor // Automatic constructor generation by Lombok
public class HelloConfig {

  private final JobBuilderFactory jobBuilderFactory;
  private final StepBuilderFactory stepBuilderFactory;

  @Bean
  public Job fooJob() {
    System.out.println("Execute fooJob method");
    return jobBuilderFactory.get("myFooJob") // Specify any unique job name
      .flow(helloStep()) // Specify any step name
      .end()
      .build();
  }

  @Bean
  public Job barJob() {
    System.out.println("Execute barJob method");
    return jobBuilderFactory.get("myBarJob") // Specify any unique job name
      .flow(helloStep()) // Specify any step name
      .next(worldStep()) // Specify any step name
      .end()
      .build();
  }

  @Bean
  public Step helloStep() {
    System.out.println("Execute helloStep method");
    return stepBuilderFactory.get("myHelloStep") // Specify any step name
      .tasklet(new MessageTasklet("Hello!")) // Specify Tasklet that will be run
      .build();
  }

  @Bean
  public Step worldStep() {
    System.out.println("Execute worldStep method");
    return stepBuilderFactory.get("myWorldStep") // Specify any unique job name
      .tasklet(new MessageTasklet("World!")) // Specify Tasklet that will be run
      .build();
  }
}

src/main/java/com/example/hello/MessageTasklet.java

package com.example.hello;

import lombok.RequiredArgsConstructor;
import org.springframework.batch.core.StepContribution;
import org.springframework.batch.core.scope.context.ChunkContext;
import org.springframework.batch.core.step.tasklet.Tasklet;
import org.springframework.batch.repeat.RepeatStatus;

// Tasklet implementation class
@RequiredArgsConstructor // Automatic constructor generation by Lombok
public class MessageTasklet implements Tasklet {

  // output message
  private final String message;

  // Method that implements concrete processing
  @Override
  public RepeatStatus execute(StepContribution contribution, ChunkContext chunkContext) throws Exception {
    System.out.println("Message: " + message); // output message
    return RepeatStatus.FINISHED; // Returns a value that indicates that processing is complete
  }
}

Build

$ gradle build

Execute

Execute myFooJob

$ java -jar build/libs/hello-batch-0.0.1.jar --spring.batch.job.names=myBarJob --logging.level.root=ERROR

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.4.2)

Execute fooJob method
Execute helloStep method
Execute barJob method
Execute worldStep method
Message: Hello!
Message: World!

Execute all jobs

    In the Spring Boot + Spring Batch configuration, all jobs will be executed unless spring.batch.job.names or spring.batch.job.enabled = false is specified.

$ java -jar build/libs/hello-batch-0.0.1.jar --logging.level.root=ERROR

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.4.2)

Execute fooJob method
Execute helloStep method
Execute barJob method
Execute worldStep method
Message: Hello!
Message: Hello!
Message: World!