Spring Batch - RepositoryItemReader read param from ExecutionContext - spring

Question

I have Spring Batch job where I am passing some values between two stpes. I set the value in Job Context in Step1 and now trying to read from RepositoryItemReader in Step2. There is #BeforeStep method where I am able to read value set in context. But I am setting up my repository along with method name and args in #PostConstruct annotated method which is executed before #BeforeStep annotated method.
What is the best way to read param in ReposiotryItem from JobExecution Context?
#Component
#JobScope
public class MyItemReader extends RepositoryItemReader<Scan> {
#Autowired
private MyRepository repository;
private Integer lastIdPulled = null;
public MyItemReader() {
super();
}
#BeforeStep
public void initializeValues(StepExecution stepExecution) {
Integer value = stepExecution.getJobExecution().getExecutionContext().getInt("lastIdPulled");
System.out.println(">>>>>>>> last_pulled_id = " + value);
}
#PostConstruct
protected void init() {
final Map<String, Sort.Direction> sorts = new HashMap<>();
sorts.put("id", Direction.ASC);
this.setRepository(this.repository);
this.setSort(sorts);
this.setMethodName("findByGreaterThanId"); // You should sepcify the method which
//spring batch should call in your repository to fetch
// data and the arguments it needs needs to be
//specified with the below method.
List<Object> methodArgs = new ArrayList<Object>();
if(lastIdPulled== null || lastIdPulled<=0 ){
lastScanIdPulled = 0;
}
methodArgs.add(lastIdPulled);
this.setArguments(methodArgs);
}
}

Answer 1

Your reader needs to be #StepScoped instead of #JobScoped. Even though you're accessing the job context, the value is not available in the context until the previous step finishes. If you #StepScope your reader then it won't initialize until the step it is part of starts up and the value is available.
Another option is to construct the reader as a #Bean definition in a #Configuration file but the idea is the same. This uses SpEL for late binding.
#Configuration
public class JobConfig {
// Your item reader will get autowired into this method
// so you don't have to call it
#Bean
public Step myStep(MyItemReader myItemReader) {
//build your step
}
#Bean
#StepScope
public MyItemReader myItemReader(#Value("#{jobExecutionContext[partitionKey]}") Integer lastIdPulled) {
MyItemReader reader = new MyItemReader();
// Perform #PostConstruct tasks
return reader;
}
}

Answer 2

I was able to figure out how to solve your problem, and mine, without having to create a #Bean definition in #Configuration file and without using #PostConstruct.
Instead of using #PostConstruct, just set them in the constructor of the class and in your #BeforeStep set the arguments as shown below:
#Component
#StepScope
public class MyItemReader extends RepositoryItemReader<Scan> {
#Autowired
public MyItemReader(MyRepository myRepository) {
super();
this.setRepository(MyRepository myRepository);
this.setMethodName("findByGreaterThanId");
final Map<String, Sort.Direction> sorts = new HashMap<>();
sorts.put("id", Direction.ASC);
this.setSort(sorts);
}
#BeforeStep
public void initializeValues(StepExecution stepExecution) {
Integer value = stepExecution.getJobExecution().getExecutionContext().getInt("lastIdPulled");
System.out.println(">>>>>>>> last_pulled_id = " + value);
List<Object> methodArgs = new ArrayList<Object>();
if(lastIdPulled== null || lastIdPulled<=0 ){
lastScanIdPulled = 0;
}
methodArgs.add(lastIdPulled);
this.setArguments(methodArgs);
}
}