TOTD #192 explained the key concepts of JSR 352. This TipOf The Day provides a working example of a how to write a simple chunk step using JSR 352 Reference Implementation integrated in GlassFish 4.
The source code for this sample application can be downloaded from here and works on GlassFish 4 b78.
As explained in TOTD #192, JSR 352 defines item-oriented processing using chunk step and task-oriented processing using batchlet step. A chunk consists of a reader that reads one item at a time, aprocessor that processes one item at a time, and a writer that aggregates 'chunk' number of items and then writes them out.
Here is an implementation of reader:
@Named
public class MyItemReader extends
AbstractItemReader<MyInputRecord> {
private final StringTokenizer
tokens;
public MyItemReader() {
tokens = new
StringTokenizer("1,2,3,4,5,6,7,8,9,10", ",");
}
@Override
public MyInputRecord readItem() {
if
(tokens.hasMoreTokens()) {
return new MyInputRecord(Integer.valueOf(tokens.nextToken()));
}
return null;
}
}Reader uses type information to specify the type of record that it is working on,
MyInputRecord in this case. The readItem
method returns null to indicate the end of items that
can be read. In this case, a StringTokenizer is used
to read the items but you can use an InputStream here
if you like.Here is an implementation of processor:
@Named
public class MyItemProcessor implements
ItemProcessor<MyInputRecord,MyOutputRecord> {
@Override
public MyOutputRecord
processItem(MyInputRecord t) {
System.out.println("processItem: " + t);
return
(t.getId() % 2 == 0) ? null : new MyOutputRecord(t.getId() * 2);
}
}Processor uses type information to specify the type of input and output records its working on,
MyInputRecord is the
input record and MyOutputRecord is the output record
in this case. The processItem method reads the input
record and accepts only odd-numbered records. This is where your
business logic would be implemented.And here is an implementation of writer:
@Named
public class MyItemWriter extends
AbstractItemWriter<MyOutputRecord> {
@Override
public void
writeItems(List<MyOutputRecord> list) {
System.out.println("writeItems: " + list);
}
}
Writer uses type information as well to specify the type of output record,
MyOutputRecord in this case. All these
elements are tied together using "Job XML" as shown:<job id="myJob" xmlns="http://batch.jsr352/jsl">
<step id="myStep">
<chunk
item-count="3">
<reader ref="myItemReader"></reader>
<processor ref="myItemProcessor"></processor>
<writer ref="myItemWriter"></writer>
</chunk>
</step>
</job>Eventually, the references
myItemReader, myItemProcessor,
and myItemWriter will be resolved using CDI. But for
now, the references can be explicitly resolved using "batch.xml" as
shown:<batch-artifacts xmlns="http://jcp.org.batch/jsl">
<ref id="myItemReader"
class="org.glassfish.chunk.simple.MyItemReader"/>
<ref id="myItemProcessor"
class="org.glassfish.chunk.simple.MyItemProcessor"/>
<ref id="myItemWriter"
class="org.glassfish.chunk.simple.MyItemWriter"/>
</batch-artifacts>Once again, downloaded the source code from here and get it running on GlassFish 4 b78.
Post feedback on public@jbatch.java.net or users@glassfish.java.net.