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Chapter 313. Spring Batch Component

Available as of Camel version 2.10

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>

313.1. URI format

spring-batch:jobName[?options]

Where jobName represents the name of the Spring Batch job located in the Camel registry. Alternatively if a JobRegistry is provided it will be used to locate the job instead.

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.

313.2. Options

The Spring Batch component supports 3 options which are listed below.

NameDescriptionDefaultType

jobLauncher (producer)

Explicitly specifies a JobLauncher to be used.

 

JobLauncher

jobRegistry (producer)

Explicitly specifies a JobRegistry to be used.

 

JobRegistry

resolveProperty Placeholders (advanced)

Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders.

true

boolean

The Spring Batch endpoint is configured using URI syntax: 

spring-batch:jobName

with the following path and query parameters:

313.2.1. Path Parameters (1 parameters):

NameDescriptionDefaultType

jobName

Required The name of the Spring Batch job located in the registry.

 

String

313.2.2. Query Parameters (4 parameters):

NameDescriptionDefaultType

jobFromHeader (producer)

Explicitly defines if the jobName should be taken from the headers instead of the URI.

false

boolean

jobLauncher (producer)

Explicitly specifies a JobLauncher to be used.

 

JobLauncher

jobRegistry (producer)

Explicitly specifies a JobRegistry to be used.

 

JobRegistry

synchronous (advanced)

Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported).

false

boolean

313.3. 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.

313.4. 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 2.11.1 JobExecution 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();

313.5. Support classes

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

313.5.1. 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>

313.5.2. 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 read data from 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>

313.5.3. 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>

313.5.4. 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>

313.6. Spring Cloud

Available as of Camel 2.19

Spring Cloud component

Maven users will need to add the following dependency to their pom.xml in order to use this component: 

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-spring-cloud</artifactId>
    <version>${camel.version}</version> <!-- use the same version as your Camel core version -->
</dependency>

camel-spring-cloud jar comes with the spring.factories file, so as soon as you add that dependency into your classpath, Spring Boot will automatically auto-configure Camel for you.

313.6.1. Camel Spring Cloud Starter

Available as of Camel 2.19

To use the starter, add the following to your spring boot pom.xml file: 

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-spring-cloud-starter</artifactId>
    <version>${camel.version}</version> <!-- use the same version as your Camel core version -->
</dependency>

313.7. Spring Cloud Consul

Available as of Camel 2.22

313.8. Spring Cloud Zookeeper

Available as of Camel 2.22

313.9. Spring Cloud Netflix

Available as of Camel 2.19

The Spring Cloud Netflix component bridges Camel Cloud and Spring Cloud Netflix so you can leverage Spring Cloud Netflix service discovery and load balance features in Camel and/or you can use Camel Service Discovery implementations as ServerList source for Spring Cloud Netflix’s Ribbon load balabncer.

Maven users will need to add the following dependency to their pom.xml in order to use this component: 

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-spring-cloud-netflix</artifactId>
    <version>${camel.version}</version>
    <!-- use the same version as your Camel core version -->
</dependency>

camel-spring-cloud-netflix jar comes with the spring.factories file, so as soon as you add that dependency into your classpath, Spring Boot will automatically auto-configure Camel for you.

You can disable Camel Spring Cloud Netflix with the following properties: 

# Enable/Disable the whole integration, default true
camel.cloud.netflix = true

# Enable/Disable the integration with Ribbon, default true
camel.cloud.netflix.ribbon = true

313.10. Spring Cloud Netflix Starter

Available as of Camel 2.19

To use the starter, add the following to your spring boot pom.xml file: 

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-spring-cloud-netflix-starter</artifactId>
    <version>${camel.version}</version>
    <!-- use the same version as your Camel core version -->
</dependency>
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