How to get currentResourceItemCount from MultiResourceItemWriter - spring

Question

org.springframework.batch.item.file.MultiResourceItemWriter saves currentResourceItemCount to executionContext, but inside the update function, which is always called before write function and as result when I am getting always currentResourceItemCount equal to 0.
What I want to achieve is to get the value of how many items have bean written to the file and put it to the footer.
public class FooterCallback extends StepExecutionListenerSupport implements FlatFileFooterCallback {
private StepExecution stepExecution;
#Override
public void writeFooter(Writer writer) throws IOException {
Integer itemCount = stepExecution.getExecutionContext().getInt("MultiResourceItemWriter.resource.item.count");
writer.write("F;" + itemCount );
}
}
Config is:
<bean id="csvGenerateWriter" class="org.springframework.batch.item.file.MultiResourceItemWriter" scope="step">
<property name="resource" value="file:#{jobExecutionContext[outputPath]}#{jobExecutionContext[outputFile]}"/>
<property name="itemCountLimitPerResource" value="3" />
<property name="delegate" ref="delegateWriter" />
</bean>
<bean id="delegateWriter" class="org.springframework.batch.item.file.FlatFileItemWriter">
<property name="footerCallback" ref="footerCallback" />
</bean>
but with the above code, I am always getting 0 in itemCount. Is is a bug or a feature? Why update furntion in MultiResourceItemWriter is not called after the write?

Answer 1

Create a custom writer with delegation; also this writer will be responsible for footer and should take care of written items count.
public class FooterWriter implements ResourceAwareItemWriterItemStream<Item>,FlatFileFooterCallback {
ResourceAwareItemWriterItemStream<Item> delegate;
int count;
public void write(List<? extends Item> items) throws Exception {
count += items.size();
delegate.write(items);
}
public void setDelegate(ResourceAwareItemWriterItemStream<Item> delegate) {
this.delegate = delegate;
}
public void writeFooter(Writer writer) throws IOException {
writer.write("F;" + count);
}
public void open(ExecutionContext executionContext) throws ItemStreamException {
count = executionContext.getInt("fwc", 0);
delegate.open(executionContext);
}
public void update(ExecutionContext executionContext) throws ItemStreamException {
executionContext.putInt("fwc", count);
delegate.update(executionContext);
}
public void close() throws ItemStreamException {
// call close() before reset count because close() calls writeFooter()!
delegate.close();
this.count = 0;
}
public void setResource(Resource resource) {
delegate.setResource(resource);
}
}
<bean id="csvGenerateWriter" class="org.springframework.batch.item.file.MultiResourceItemWriter" scope="step">
<property name="resource" value="file:output.txt"/>
<property name="itemCountLimitPerResource" value="3" />
<property name="delegate" ref="delegateWriter" />
</bean>
<bean id="flatFileItemWriter" class="org.springframework.batch.item.file.FlatFileItemWriter">
<property name="footerCallback" ref="delegateWriter" />
<property name="lineAggregator">
<bean class="org.springframework.batch.item.file.transform.PassThroughLineAggregator" />
</property>
</bean>
<bean id="delegateWriter" class="footercallback.FooterWriter">
<property name="delegate" ref="flatFileItemWriter" />
</bean>