Spring Batch With Annotation and Caching

Question

Does anyone have good example of Spring Batch (Using Annotation) to cache a reference table which will be accessible to processor ?

I just need a simple cache, run a query which returns some byte[] and keep it in memory till the time job is executing.

Appreciate any help on this topic.

Thanks !

Answer 1

A JobExecutionListener can be used to populate the cache with reference data before the job is executed and clear the cache after the job is finished.

Here is an example:

import org.springframework.batch.core.Job;
import org.springframework.batch.core.JobExecution;
import org.springframework.batch.core.JobExecutionListener;
import org.springframework.batch.core.JobParameters;
import org.springframework.batch.core.Step;
import org.springframework.batch.core.StepContribution;
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.core.scope.context.ChunkContext;
import org.springframework.batch.core.step.tasklet.Tasklet;
import org.springframework.batch.repeat.RepeatStatus;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.CacheManager;
import org.springframework.cache.concurrent.ConcurrentMapCacheManager;
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 {

    private JobBuilderFactory jobs;

    private StepBuilderFactory steps;

    public MyJob(JobBuilderFactory jobs, StepBuilderFactory steps) {
       this.jobs = jobs;
       this.steps = steps;
    }

    @Bean
    public CacheManager cacheManager() {
        return new ConcurrentMapCacheManager(); // return the implementation you want
    }

    @Bean
    public Tasklet tasklet() {
        return new MyTasklet(cacheManager());
    }

    @Bean
    public Step step() {
        return steps.get("step")
                .tasklet(tasklet())
                .build();
    }

    @Bean
    public JobExecutionListener jobExecutionListener() {
        return new CachingJobExecutionListener(cacheManager());
    }

    @Bean
    public Job job() {
        return jobs.get("job")
                .start(step())
                .listener(jobExecutionListener())
                .build();
    }

    class MyTasklet implements Tasklet {

        private CacheManager cacheManager;

        public MyTasklet(CacheManager cacheManager) {
            this.cacheManager = cacheManager;
        }

        @Override
        public RepeatStatus execute(StepContribution contribution, ChunkContext chunkContext) throws Exception {
            String name = (String) cacheManager.getCache("referenceData").get("foo").get();
            System.out.println("Hello " + name);
            return RepeatStatus.FINISHED;
        }
    }

    class CachingJobExecutionListener implements JobExecutionListener {

        private CacheManager cacheManager;

        public CachingJobExecutionListener(CacheManager cacheManager) {
            this.cacheManager = cacheManager;
        }

        @Override
        public void beforeJob(JobExecution jobExecution) {
            // populate cache as needed. Can use a jdbcTemplate to query the db here and populate the cache
            cacheManager.getCache("referenceData").put("foo", "bar");
        }

        @Override
        public void afterJob(JobExecution jobExecution) {
            // clear cache when the job is finished
            cacheManager.getCache("referenceData").clear();
        }
    }

    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());
    }

}

When executed, it prints:

Hello bar

which means data is correctly retrieved from the cache. You would need to adapt the sample to query the database and populate the cache (See comments in code).

Hope this helps.