Spring Batch process different types in one step - spring-batch

Question

I have a batch job that reads records from a file. I want to convert said records to PojoA (all strings). I want to run each record throw a validator ensure all fields are present. I then want to transform PojoA to PojoB. The issue I have is that I am unable to change the type of object mid-step.
return getStepBuilder("downloadData")
.<PojoA, PojoA>chunk(1000)
.reader(pojoAReader())
.processor(pojoAValidator)
.writer(pojoAWriter)
.processor(pojoAToPojoBTransformer) <- issue here, <PojoA, PojoB>
.write(pojoBWriter)
.build();
The reason PojoB exists is because PojoA is all strings; I want to persist all records regardless if they're invalid. PojoB has the accurate data types, e.g. Dates, numbers.
I think I need another step that deals with but how do I pass the PojoA's to step 2?

Answer 1

You cannot declare two processors/writers like:
.processor(pojoAValidator)
.writer(pojoAWriter)
.processor(pojoAToPojoBTransformer) <- issue here, <PojoA, PojoB>
.write(pojoBWriter)
You need to use a composite processor/writer for that.
Here is a quick example for a composite processor with processor1 (Integer -> Integer) then processor2 (Integer -> String):
import java.util.Arrays;
import org.springframework.batch.core.Job;
import org.springframework.batch.core.JobParameters;
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.batch.core.launch.JobLauncher;
import org.springframework.batch.item.ItemProcessor;
import org.springframework.batch.item.ItemReader;
import org.springframework.batch.item.ItemWriter;
import org.springframework.batch.item.support.CompositeItemProcessor;
import org.springframework.batch.item.support.ListItemReader;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
#Configuration
#EnableBatchProcessing
public class MyJob {
#Autowired
private JobBuilderFactory jobs;
#Autowired
private StepBuilderFactory steps;
#Bean
public ItemReader<Integer> itemReader() {
return new ListItemReader<>(Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10));
}
#Bean
public ItemWriter<String> itemWriter() {
return items -> {
for (String item : items) {
System.out.println("item = " + item);
}
};
}
#Bean
public ItemProcessor<Integer, Integer> itemProcessor1() {
return item -> item + 1;
}
#Bean
public ItemProcessor<Integer, String> itemProcessor2() {
return String::valueOf;
}
#Bean
public ItemProcessor<Integer, String> compositeItemProcessor() {
CompositeItemProcessor<Integer, String> compositeItemProcessor = new CompositeItemProcessor<>();
compositeItemProcessor.setDelegates(Arrays.asList(itemProcessor1(), itemProcessor2()));
return compositeItemProcessor;
}
#Bean
public Step step() {
return steps.get("step")
.<Integer, String>chunk(5)
.reader(itemReader())
.processor(compositeItemProcessor())
.writer(itemWriter())
.build();
}
#Bean
public Job job() {
return jobs.get("job")
.start(step())
.build();
}
public static void main(String[] args) throws Exception {
ApplicationContext context = new AnnotationConfigApplicationContext(MyJob.class);
JobLauncher jobLauncher = context.getBean(JobLauncher.class);
Job job = context.getBean(Job.class);
jobLauncher.run(job, new JobParameters());
}
}