Spring Batch - Spring Enterprise Recipes: A Problem Solution Approach - page 376

How It Works

Launching a Job with Parameters
A job is a prototype of a JobInstance . JobParameters are used to provide a way of identifying a unique
run of a job (a JobInstance ). These JobParameters allow you to give input to your batch process, just
as you would with a method definition in Java. You've seen the JobParameters in previous examples,
but not in detail. The JobParameters object is created as you launch the job using the JobLauncher . To
launch a job called dailySalesFigures , with the date for the job to work with, you would write something
like this:

ClassPathXmlApplicationContext classPathXmlApplicationContext = new
ClassPathXmlApplicationContext("solution2.xml");
classPathXmlApplicationContext.start();
JobLauncher jobLauncher = (JobLauncher) classPathXmlApplicationContext. ➥

getBean("jobLauncher");
Job job = (Job) classPathXmlApplicationContext.getBean("dailySalesFigures");
jobLauncher.run(job, new JobParametersBuilder().addDate( "date",
DateUtils.truncate(new Date(), Calendar.DATE)).toJobParameters());

Accessing JobParameters
Technically, you can get at JobParameters via any of the ExecutionContexts ( step , job , and so on). Once
you have it, you can access the parameters in a type-safe way by calling getLong() , getString() , and so
on. A simple way to do this is to bind to the @BeforeStep event, save the StepExecution , and iterate over
the parameters this way. From here, you can inspect the parameters and do anything you want with
them. Let's look at that in terms of the ItemProcessor you wrote earlier:

// …
private StepExecution stepExecution;

@BeforeStep
public void saveStepExecution(StepExecution stepExecution) {
this.stepExecution = stepExecution;
}

public UserRegistration process(UserRegistration input) throws Exception {

Map<String, JobParameter> params = stepExecution.getJobParameters(). ➥

getParameters();

// iterate over all of the parameters
for (String jobParameterKey : params.keySet()) {
System.out.println(String.format("%s=%s", jobParameterKey,
params.get(jobParameterKey).getValue().toString()));
}

// access specific parameters in a type safe way
Date date = stepExecution.getJobParameters().getDate("date");
// etc …
}