How to skip reader, writer in spring batch - spring

Question

I have a requirement where I need to upload some files to a server. I am using spring batch to accomplish the same. Here the "initializeFile" will basically interact with the server to check if the files already exists in server. if not then it should call the step "uploadIndexFileStep" to upload the files. If files already present in server then the step "uploadIndexFileStep" SHOULDN'T be called.
How to implement this case wherein if the "initializeFile" has no files to upload then spring should not call the next step "uploadIndexFileStep".
Is there a way, or do I need to follow some design or its a spring config change? Any pointers would be helpful.
following is the batch configuration.
<batch:step id="initFileStep" next="uploadIndexFileStep">
<batch:tasklet ref="initializeFile"></batch:tasklet>
</batch:step>
<batch:step id="uploadIndexFileStep">
<batch:tasklet>
<batch:chunk reader="indexFileReader" processor="indexFileProcessor" writer="indexFileWriter" commit-interval="${app.chunk.commit.interval}"/>
</batch:tasklet>
</batch:step>
<batch:listeners>
<batch:listener ref="uploadIndexJobListener"/>
</batch:listeners>
</batch:job>

Answer 1

Spring batch provides a nice way to handle conditional flow. You can implement this by using ON exist status.
You can have something like below
#Bean
public Job job() {
return jobBuilderFactory().get("job").
flow(initializeFile()).on("FILELOADED").to(anyStep()).
from(initializeFile()).on("FILENOTLOADED").to(uploadIndexFileStep()).next(step3()).next(step4()).end().build();
}
5.3.2 Conditional Flow

Answer 2

I resolved this using JobExecutionDecider. I am maintaining the queue size in ExecutionContext and then reading this execution context in decider to manage the flow.
public class UploadIndexFlowDecider implements JobExecutionDecider {
#Override
public FlowExecutionStatus decide(JobExecution jobExecution, StepExecution stepExecution) {
int queueSize = jobExecution.getExecutionContext().getInt("INDEX_UPLOAD_QUEUE_SIZE");
if(queueSize > 0)
return FlowExecutionStatus.COMPLETED;
else
return FlowExecutionStatus.STOPPED;
}
}
#Component
public class InitializeFileStep implements Tasklet {
#Override
public RepeatStatus execute(StepContribution contribution, ChunkContext chunkContext) throws Exception {
chunkContext.getStepContext().getStepExecution().getJobExecution().getExecutionContext().putInt("INDEX_UPLOAD_QUEUE_SIZE", 1);
return RepeatStatus.FINISHED;
}
<batch:job id="uploadIndexFileJob">
<batch:step id="initFileStep" next="uploadDecision">
<batch:tasklet ref="initializeFile"></batch:tasklet>
</batch:step>
<batch:decision id="uploadDecision" decider="uploadIndexDecision">
<batch:next on="COMPLETED" to="uploadIndexFileStep"/>
<batch:end on="STOPPED"/>
</batch:decision>
<batch:step id="uploadIndexFileStep">
<batch:tasklet>
<batch:chunk reader="indexFileReader" processor="indexFileProcessor" writer="indexFileWriter" commit-interval="${app.chunk.commit.interval}"/>
</batch:tasklet>
</batch:step>
<batch:listeners>
<batch:listener ref="uploadIndexJobListener"/>
</batch:listeners>
</batch:job>