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Chapter 159. SpringBatch

Spring Batch Component

The spring-batch: component and support classes provide integration bridge between Camel and Spring Batch infrastructure.
Maven users will need to add the following dependency to their pom.xml for this component: 
<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-spring-batch</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>

URI format

spring-batch:jobName[?options]
Where jobName represents the name of the Spring Batch job located in the Camel registry.
Warning
This component can only be used to define producer endpoints, which means that you cannot use the Spring Batch component in a from() statement.

Options

Name Default Value Description
jobLauncherRef null Deprecated and will be removed in Camel 3.0!Camel 2.10: Use jobLauncher=#theName instead.
jobLauncher null Camel 2.11.1: Explicitly specifies a JobLauncher to be used from the Camel Registry.

Usage

When Spring Batch component receives the message, it triggers the job execution. The job will be executed using the org.springframework.batch.core.launch.JobLaucher instance resolved according to the following algorithm:
  • if JobLauncher is manually set on the component, then use it.
  • if jobLauncherRef option is set on the component, then search Camel Registry for the JobLauncher with the given name. Deprecated and will be removed in Camel 3.0!
  • if there is JobLauncher registered in the Camel Registry under jobLauncher name, then use it.
  • if none of the steps above allow to resolve the JobLauncher and there is exactly one JobLauncher instance in the Camel Registry, then use it.
All headers found in the message are passed to the JobLauncher as job parameters. String, Long, Double and java.util.Date values are copied to the org.springframework.batch.core.JobParametersBuilder - other data types are converted to Strings.

Examples

Triggering the Spring Batch job execution: 
from("direct:startBatch").to("spring-batch:myJob");
Triggering the Spring Batch job execution with the JobLauncher set explicitly. 
from("direct:startBatch").to("spring-batch:myJob?jobLauncherRef=myJobLauncher");
Starting from the Camel 2.11.1JobExecution instance returned by the JobLauncher is forwarded by the SpringBatchProducer as the output message. You can use the JobExecution instance to perform some operations using the Spring Batch API directly. 
from("direct:startBatch").to("spring-batch:myJob").to("mock:JobExecutions");
...
MockEndpoint mockEndpoint = ...;
JobExecution jobExecution = mockEndpoint.getExchanges().get(0).getIn().getBody(JobExecution.class);
BatchStatus currentJobStatus = jobExecution.getStatus();

Support classes

Apart from the Component, Camel Spring Batch provides also support classes, which can be used to hook into Spring Batch infrastructure.

CamelItemReader

CamelItemReader can be used to read batch data directly from the Camel infrastructure.
For example the snippet below configures Spring Batch to read data from JMS queue. 
<bean id="camelReader" class="org.apache.camel.component.spring.batch.support.CamelItemReader">
  <constructor-arg ref="consumerTemplate"/>
  <constructor-arg value="jms:dataQueue"/>
</bean>

<batch:job id="myJob">
  <batch:step id="step">
    <batch:tasklet>
      <batch:chunk reader="camelReader" writer="someWriter" commit-interval="100"/>
    </batch:tasklet>
  </batch:step>
</batch:job>

CamelItemWriter

CamelItemWriter has similar purpose as CamelItemReader, but it is dedicated to write chunk of the processed data.
For example the snippet below configures Spring Batch to write data to a JMS queue. 
<bean id="camelwriter" class="org.apache.camel.component.spring.batch.support.CamelItemWriter">
  <constructor-arg ref="producerTemplate"/>
  <constructor-arg value="jms:dataQueue"/>
</bean>

<batch:job id="myJob">
  <batch:step id="step">
    <batch:tasklet>
      <batch:chunk reader="someReader" writer="camelwriter" commit-interval="100"/>
    </batch:tasklet>
  </batch:step>
</batch:job>

CamelItemProcessor

CamelItemProcessor is the implementation of Spring Batch org.springframework.batch.item.ItemProcessor interface. The latter implementation relays on Request Reply pattern to delegate the processing of the batch item to the Camel infrastructure. The item to process is sent to the Camel endpoint as the body of the message.
For example the snippet below performs simple processing of the batch item using the Direct endpoint and the Simple expression language. 
<camel:camelContext>
  <camel:route>
    <camel:from uri="direct:processor"/>
    <camel:setExchangePattern pattern="InOut"/>
    <camel:setBody>
      <camel:simple>Processed ${body}</camel:simple>
    </camel:setBody>
  </camel:route>
</camel:camelContext>

<bean id="camelProcessor" class="org.apache.camel.component.spring.batch.support.CamelItemProcessor">
  <constructor-arg ref="producerTemplate"/>
  <constructor-arg value="direct:processor"/>
</bean>

<batch:job id="myJob">
  <batch:step id="step">
    <batch:tasklet>
      <batch:chunk reader="someReader" writer="someWriter" processor="camelProcessor" commit-interval="100"/>
    </batch:tasklet>
  </batch:step>
</batch:job>

CamelJobExecutionListener

CamelJobExecutionListener is the implementation of the org.springframework.batch.core.JobExecutionListener interface sending job execution events to the Camel endpoint.
The org.springframework.batch.core.JobExecution instance produced by the Spring Batch is sent as a body of the message. To distinguish between before- and after-callbacks SPRING_BATCH_JOB_EVENT_TYPE header is set to the BEFORE or AFTER value.
The example snippet below sends Spring Batch job execution events to the JMS queue. 
<bean id="camelJobExecutionListener" class="org.apache.camel.component.spring.batch.support.CamelJobExecutionListener">
  <constructor-arg ref="producerTemplate"/>
  <constructor-arg value="jms:batchEventsBus"/>
</bean>

<batch:job id="myJob">
  <batch:step id="step">
    <batch:tasklet>
      <batch:chunk reader="someReader" writer="someWriter" commit-interval="100"/>
    </batch:tasklet>
  </batch:step>
  <batch:listeners>
    <batch:listener ref="camelJobExecutionListener"/>
  </batch:listeners>
</batch:job>