Item Writers - Spring Batch - page 317

delegate.open(executionContext);
}
@Override
public void update(ExecutionContext executionContext)
throws ItemStreamException {
executionContext.put("records.processed", itemsProcessedSoFar);
delegate.update(executionContext);
}
@Override
public void setResource(Resource arg0) {
itemsProcessedSoFar = 0;
delegate.setResource(arg0);
}
}
As you can see in Listing 9-72 when a resource is set on the ItemWriter, the counter
( itemsProcessedSoFar ) is set to 0. As items are written via the write method, the counter is incremented
accordingly. When the writeFooter method is called, the counter is used in the footer output to list the
number of records that are in the file that is being closed.
There are three other methods to take note of in this implementation: open , update , and close . The
open and update methods end up being more than just passthroughs to make this ItemWriter restartable.
Because the ItemWriter has its own state (the number of records that have been processed in the current
file), you want to save that in the ExecutionContext in case the job fails. The update method is used to
save that value during processing. The open method is used to reset where you left off in the event the job
is restarted. The close method serves as only a passthrough to the delegate so that it can close the file as
required.
To configure the various ItemWriters required for this example, Listing 9-73 shows the required
XML. You begin with the input, reading the customer records out of the Customer table. From there, you
configure the three ItemWriter implementations. The first is FlatFileItemWriter and its required
LineAggregator . From there, you configure customerWriter , which is the implementation of the
ItemWriter ( ResourceAwareItemReaderItemStream is a sub-interface of the ItemReader interface) in
Listing 9-72. Finally, you have the multiResourceItemWriter you've used previously. Listing 9-73 finishes
with the configuration of the step and job.
Listing 9-73. customerFooterFormatJob.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans:beans xmlns=" http://www.springframework.org/schema/batch"
xmlns:beans=" http://www.springframework.org/schema/beans"
xmlns:util=" http://www.springframework.org/schema/beans"
xmlns:xsi=" http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation=" http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/util
http://www.springframework.org/schema/util/spring-util.xsd
http://www.springframework.org/schema/batch
http://www.springframework.org/schema/batch/spring-batch-2.1.xsd">
<beans:import resource="../launch-context.xml"/>