How to write a spring batch step without an itemwriter

For chunk-based step reader and writer are mandatory.
If you don't want a writer use a No-operation ItemWriter that does nothing.

EDIT:
A no-op implementation is an empty implementation of interface tha does...nothing!
Just let your class implements desiderable inteface(s) with empty methods.

No-op ItemWriter:

public class NoOpItemWriter implements ItemWriter {
  void write(java.util.List<? extends T> items) throws java.lang.Exception {
    // no-op
  }
}

I hope you got answer but I want to explain it for other readers, When we use chunk then usually we declare reader, processor and writer. In chunk reader and writer are mandatory and processor is optional. In your case if you don't need writer then u need to make a class which implements ItemWriter. Override write method and keep it blank. Now create a bean of writer class and pass it as reference of writer.

<batch:step id="recordProcessingStep" >
        <batch:tasklet>
            <batch:chunk reader="fileReader" processor="recordProcessor"
                writer="rocordWriter" commit-interval="1" />
        </batch:tasklet>
    </batch:step>

Your writer class will look like .

public class RecordWriter<T> implements ItemWriter<T> {
@Override
public void write(List<? extends T> items) throws Exception {
    // TODO Auto-generated method stub

}

}