batch applications for the java platform


Batch Applications for the Java PlatformSivakumar ThyagarajanOracle [email protected]


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Batch Applications for the Java Platform

Standardizes batch processing for Java– Non-interactive, bulk-oriented, long-running

– Data pr computationally intensive

– Sequentially or in parallel

– Ad-hoc, scheduled or on-demand execution

Led by IBM Spring Batch, WebSphere Compute Grid (WCG), z/OS Batch Part of Java EE 7, can be used in Java SE


JBatch Domain Language


Reader, Processor, Writerpublic interface ItemReader<T> { public void open(Externalizable checkpoint); public T readItem(); public Externalizable checkpointInfo(); public void close();}

public interface ItemProcessor<T, R> { public R processItem(T item);}

public interface ItemWriter<T> { public void open(Externalizable checkpoint); public void writeItems(List<T> items); public Externalizable checkpointInfo(); public void close();}


//For a job<step id=”sendStatements”> <chunk reader=”accountReader” processor=”accountProcessor” writer=”emailWriter” item-count=”10” /></step>

Batch Applications for the Java Platform Step Example using Job Specification Language (JSL)

@Named(“accountReader")...implements ItemReader... {public Account readItem() { // read account using JPA

@Named(“accountProcessor")...implements ItemProcessor... {Public Statement processItems(Account account) { // read Account, return Statement

@Named(“emailWriter")...implements ItemWriter... {public void writeItems(List<Statements> statements) { // use JavaMail to send email


Batch Chunks


Checkpointing

For data intensive tasks, long periods of time– Checkpoint/restart is a common design requirement

Basically saves Reader, Writer positions– Naturally fits into Chunk oriented steps

– reader.checkpointInfo() and writer.checkpointInfo() are called

– The resulting Externalizable data is persisted

– When the Chunk restarts, the reader and writer are initialized with the respective Externalizable data


Reader, Processor, Writerpublic interface ItemReader<T> { public void open(Externalizable checkpoint); public T readItem(); public Externalizable checkpointInfo(); public void close();}

public interface ItemProcessor<T, R> { public R processItem(T item);}

public interface ItemWriter<T> { public void open(Externalizable checkpoint); public void writeItems(List<T> items); public Externalizable checkpointInfo(); public void close();}


Handling Exceptions

<job id=...>... <chunk skip-limit=”5” retry-limit=”5”> <skippable-exception-classes> <include class="java.lang.Exception"/> <exclude class="java.io.FileNotFoundException"/> </skippable-exception-classes> <retryable-exception-classes> </retryable-exception-classes> <no-rollback-exception-classes> </no-rollback-exception-classes> </chunk>...</job>


Partitioned Step

A batch step may run as a partitioned step– A partitioned step runs as multiple instances of the same step definition

across multiple threads, one partition per thread

<step id="step1" > <chunk ...> <partition> <plan partitions=“10" threads="2"/> <reducer .../> </partition> </chunk></step>


Partitioning – Advanced Scenarios

Partition Mapper– Dynamically decide number of partitions (partition plan)

Partition Reducer

– Demarcate logical unit of work around partition processing Partition Collector

– Sends interim results from individual partition to step's partition analyzer

Partition Analyzer

– Collection point of interim results, single point of control and analysis


Flow and Split

Flow defines a set of steps to be executed as a unit<flow id=”flow-1" next=“{flow, step, decision}-id” > <step id=“flow_1_step_1”> </step> <step id=“flow_1_step_2”> </step></flow>

Split defines a set of flows to be executed in parallel

<split …> <flow …./> <!– each flow runs on a separate thread --> <flow …./></split>


Batchlet

Task oriented unit of work Doesn't support resume Not item-oriented Simple Batchlet interface – process(), stop() In job xml:<batchlet ref=”{name}”/>


Programming Model – Advanced Scenarios

CheckpointAlgorithm Decider Listeners – Job, Step, Chunk Listeners … @BatchProperty

String fname = “/tmp/default.txt” @BatchContext

JobContext jctxt;


Batch Runtime Specification

JobOperator interface – for programmatic lifecycle control of jobs Step level Metrics through the StepExecution object Batch Artifact loading through META-INF/batch.xml Job XML loading through META-INF/batch-jobs/my-job.xml Packaging – jar, war, ejb-jar


Example: Programmatic Invocation of Jobs

In a Servlet/EJB:

import javax.batch.runtime.BatchRuntime;...

JobOperator jo = BatchRuntime.getJobOperator();jo.start("myJob", new Properties());

...


Example: META-INF/batch-jobs/my-job.xml

<job id="myJob" xmlns="http://batch.jsr352/jsl"> <step id="myStep"> <chunk item-count="3"> <reader ref="myItemReader"/> <processor ref="myItemProcessor"/> <writer ref="myItemWriter"/> </chunk> </step></job>

If in a WAR, this would be WEB-INF/classes/META-INF/batch-jobs/my-job.xml


Example: META-INF/batch.xml

<batch-artifacts xmlns="http://jcp.org.batch/jsl"> <ref id="myItemReader" class="org.acme.MyItemReader"/> <ref id="myItemProcessor" class="org.acme.MyItemProcessor"/> <ref id="myItemWriter" class="org.acme.MyItemWriter"/></batch-artifacts>

If in a WAR, this would be WEB-INF/classes/META-INF/batch.xml


Where to Find Out More

Read the final spec and API docs at http://java.net/projects/jbatch/ Join [email protected] and send questions and comments RI integrated in GlassFish 4.0

– http://glassfish.java.net/

– http://dlc.sun.com.edgesuite.net/glassfish/4.0/promoted/

http://java.net/projects/jbatch/

mailto:[email protected]

http://glassfish.java.net/

http://dlc.sun.com.edgesuite.net/glassfish/4.0/promoted/


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batch applications for the java platform

Technology

public void writeitems

public void close

read account

public externalizable checkpointinfo

externalizable checkpoint

rights reserved

list items

public