Should Job/Step/Reader/Writer all be bean? - spring-batch

Question

As fars as all the examples from the Spring Batch reference doc , I see that those objects like job/step/reader/writer are all marked as #bean, like the following:
#Bean
public Job footballJob() {
return this.jobBuilderFactory.get("footballJob")
.listener(sampleListener())
...
.build();
}
#Bean
public Step sampleStep(PlatformTransactionManager transactionManager) {
return this.stepBuilderFactory.get("sampleStep")
.transactionManager(transactionManager)
.<String, String>chunk(10)
.reader(itemReader())
.writer(itemWriter())
.build();
}
I have a scenario that the server side will receive requests and run job concurrently(different job names or same job name with different jobparameters). The usage is to new a job object(including steps/reader/writers) in concurrent threads, so I propabaly will not state the job method as #bean and new a job each time.
And there is actually a differenence on how to transmit parameters to object like reader. If using #bean , parameters must be put in e.g. JobParameters to be late binding into object using #StepScope, like the following example:
#StepScope
#Bean
public FlatFileItemReader flatFileItemReader(#Value(
"#{jobParameters['input.file.name']}") String name) {
return new FlatFileItemReaderBuilder<Foo>()
.name("flatFileItemReader")
.resource(new FileSystemResource(name))
}
If not using #bean , I can just transmit parameter directly with no need to put data into JobParameter,like the following
public FlatFileItemReader flatFileItemReader(String name) {
return new FlatFileItemReaderBuilder<Foo>()
.name("flatFileItemReader")
.resource(new FileSystemResource(name))
}
Simple test shows that no #bean works. But I want to confirm formally:
1、 Is using #bean at job/step/reader/writer mandatory or not ?
2、 if it is not mandatory, when I new a object like reader, do I need to call afterPropertiesSet() manually?
Thanks!

Answer 1

1、 Is using #bean at job/step/reader/writer mandatory or not ?
No, it is not mandatory to declare batch artefacts as beans. But you would want to at least declare the Job as a bean to benefit from Spring's dependency injection (like injecting the job repository reference into the job, etc) and be able to do something like:
ApplicationContext context = new AnnotationConfigApplicationContext(MyJobConfig.class);
Job job = context.getBean(Job.class);
JobLauncher jobLauncher = context.getBean(JobLauncher.class);
jobLauncher.run(job, new JobParameters());
2、 if it is not mandatory, when I new a object like reader, do I need to call afterPropertiesSet() manually?
I guess that by "when I new a object like reader" you mean create a new instance manually. In this case yes, if the object is not managed by Spring, you need to call that method yourself. If the object is declared as a bean, Spring will call
the afterPropertiesSet() method automatically. Here is a quick sample:
import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
#Configuration
public class TestAfterPropertiesSet {
#Bean
public MyBean myBean() {
return new MyBean();
}
public static void main(String[] args) throws Exception {
ApplicationContext context = new AnnotationConfigApplicationContext(TestAfterPropertiesSet.class);
MyBean myBean = context.getBean(MyBean.class);
myBean.sayHello();
}
static class MyBean implements InitializingBean {
#Override
public void afterPropertiesSet() throws Exception {
System.out.println("MyBean.afterPropertiesSet");
}
public void sayHello() {
System.out.println("Hello");
}
}
}
This prints:
MyBean.afterPropertiesSet
Hello