## Spring Batch Integration

XML Java Both

### Spring Batch Integration Introduction

Many users of Spring Batch may encounter requirements that are outside the scope of Spring Batch but that may be efficiently and concisely implemented by using Spring Integration. Conversely, Spring Integration users may encounter Spring Batch requirements and need a way to efficiently integrate both frameworks. In this context, several patterns and use-cases emerge, and Spring Batch Integration addresses those requirements.

The line between Spring Batch and Spring Integration is not always clear, but two pieces of advice can help: Think about granularity, and apply common patterns. Some of those common patterns are described in this reference manual section.

Adding messaging to a batch process enables automation of operations and also separation and strategizing of key concerns. For example, a message might trigger a job to execute, and then the sending of the message can be exposed in a variety of ways. Alternatively, when a job completes or fails, that event might trigger a message to be sent, and the consumers of those messages might have operational concerns that have nothing to do with the application itself. Messaging can also be embedded in a job (for example reading or writing items for processing via channels). Remote partitioning and remote chunking provide methods to distribute workloads over a number of workers.

This section covers the following key concepts:

- Namespace Support

- Launching Batch Jobs through Messages

- Providing Feedback with Informational Messages

- Asynchronous Processors

- Externalizing Batch Process Execution

#### Namespace Support

Since Spring Batch Integration 1.3, dedicated XML Namespace support was added, with the aim to provide an easier configuration experience. In order to activate the namespace, add the following namespace declarations to your Spring XML Application Context file:

    <beans xmlns="http://www.springframework.org/schema/beans"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xmlns:batch-int="http://www.springframework.org/schema/batch-integration"
      xsi:schemaLocation="
        http://www.springframework.org/schema/batch-integration
        https://www.springframework.org/schema/batch-integration/spring-batch-integration.xsd">

        ...

    </beans>

A fully configured Spring XML Application Context file for Spring Batch Integration may look like the following:

    <beans xmlns="http://www.springframework.org/schema/beans"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xmlns:int="http://www.springframework.org/schema/integration"
      xmlns:batch="http://www.springframework.org/schema/batch"
      xmlns:batch-int="http://www.springframework.org/schema/batch-integration"
      xsi:schemaLocation="
        http://www.springframework.org/schema/batch-integration
        https://www.springframework.org/schema/batch-integration/spring-batch-integration.xsd
        http://www.springframework.org/schema/batch
        https://www.springframework.org/schema/batch/spring-batch.xsd
        http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/integration
        https://www.springframework.org/schema/integration/spring-integration.xsd">

        ...

    </beans>

Appending version numbers to the referenced XSD file is also allowed, but, as a version-less declaration always uses the latest schema, we generally do not recommend appending the version number to the XSD name. Adding a version number could possibly create issues when updating the Spring Batch Integration dependencies, as they may require more recent versions of the XML schema.

#### Launching Batch Jobs through Messages

When starting batch jobs by using the core Spring Batch API, you basically have 2 options:

- From the command line, with the `CommandLineJobRunner`

- Programmatically, with either `JobOperator.start()` or `JobLauncher.run()`

For example, you may want to use the `CommandLineJobRunner` when invoking Batch Jobs by using a shell script. Alternatively, you may use the `JobOperator` directly (for example, when using Spring Batch as part of a web application). However, what about more complex use cases? Maybe you need to poll a remote (S)FTP server to retrieve the data for the Batch Job or your application has to support multiple different data sources simultaneously. For example, you may receive data files not only from the web, but also from FTP and other sources. Maybe additional transformation of the input files is needed before invoking Spring Batch.

Therefore, it would be much more powerful to execute the batch job using Spring Integration and its numerous adapters. For example, you can use a File Inbound Channel Adapter to monitor a directory in the file-system and start the Batch Job as soon as the input file arrives. Additionally, you can create Spring Integration flows that use multiple different adapters to easily ingest data for your batch jobs from multiple sources simultaneously using only configuration. Implementing all these scenarios with Spring Integration is easy, as it allows for decoupled, event-driven execution of the `JobLauncher`.

Spring Batch Integration provides the `JobLaunchingMessageHandler` class that you can use to launch batch jobs. The input for the `JobLaunchingMessageHandler` is provided by a Spring Integration message, which has a payload of type `JobLaunchRequest`. This class is a wrapper around the `Job` that needs to be launched and around the `JobParameters` necessary to launch the Batch job.

The following image illustrates the typical Spring Integration message flow in order to start a Batch job. The EIP (Enterprise Integration Patterns) website provides a full overview of messaging icons and their descriptions.

Figure 1. Launch Batch Job

##### Transforming a file into a JobLaunchRequest

    package io.spring.sbi;

    import org.springframework.batch.core.Job;
    import org.springframework.batch.core.JobParametersBuilder;
    import org.springframework.batch.integration.launch.JobLaunchRequest;
    import org.springframework.integration.annotation.Transformer;
    import org.springframework.messaging.Message;

    import java.io.File;

    public class FileMessageToJobRequest {
        private Job job;
        private String fileParameterName;

        public void setFileParameterName(String fileParameterName) {
            this.fileParameterName = fileParameterName;
        }

        public void setJob(Job job) {
            this.job = job;
        }

        @Transformer
        public JobLaunchRequest toRequest(Message<File> message) {
            JobParametersBuilder jobParametersBuilder =
                new JobParametersBuilder();

            jobParametersBuilder.addString(fileParameterName,
                message.getPayload().getAbsolutePath());

            return new JobLaunchRequest(job, jobParametersBuilder.toJobParameters());
        }
    }

##### The `JobExecution` Response

When a batch job is being executed, a `JobExecution` instance is returned. This instance can be used to determine the status of an execution. If a `JobExecution` is able to be created successfully, it is always returned, regardless of whether or not the actual execution is successful.

The exact behavior on how the `JobExecution` instance is returned depends on the provided `TaskExecutor`. If a `synchronous` (single-threaded) `TaskExecutor` implementation is used, the `JobExecution` response is returned only `after` the job completes. When using an `asynchronous` `TaskExecutor`, the `JobExecution` instance is returned immediately. Users can then take the `id` of `JobExecution` instance (with `JobExecution.getJobId()`) and query the `JobRepository` for the job’s updated status using the `JobExplorer`. For more information, please refer to the Spring Batch reference documentation on Querying the Repository.

##### Spring Batch Integration Configuration

Consider a case where someone needs to create a file `inbound-channel-adapter` to listen for CSV files in the provided directory, hand them off to a transformer (`FileMessageToJobRequest`), launch the job through the Job Launching Gateway, and then log the output of the `JobExecution` with the `logging-channel-adapter`.

The following example shows how that common case can be configured in XML:

XML Configuration

    <int:channel id="inboundFileChannel"/>
    <int:channel id="outboundJobRequestChannel"/>
    <int:channel id="jobLaunchReplyChannel"/>

    <int-file:inbound-channel-adapter id="filePoller"
        channel="inboundFileChannel"
        directory="file:/tmp/myfiles/"
        filename-pattern="*.csv">
      <int:poller fixed-rate="1000"/>
    </int-file:inbound-channel-adapter>

    <int:transformer input-channel="inboundFileChannel"
        output-channel="outboundJobRequestChannel">
      <bean class="io.spring.sbi.FileMessageToJobRequest">
        <property name="job" ref="personJob"/>
        <property name="fileParameterName" value="input.file.name"/>
      </bean>
    </int:transformer>

    <batch-int:job-launching-gateway request-channel="outboundJobRequestChannel"
        reply-channel="jobLaunchReplyChannel"/>

    <int:logging-channel-adapter channel="jobLaunchReplyChannel"/>

The following example shows how that common case can be configured in Java:

Java Configuration

    @Bean
    public FileMessageToJobRequest fileMessageToJobRequest() {
        FileMessageToJobRequest fileMessageToJobRequest = new FileMessageToJobRequest();
        fileMessageToJobRequest.setFileParameterName("input.file.name");
        fileMessageToJobRequest.setJob(personJob());
        return fileMessageToJobRequest;
    }

    @Bean
    public JobLaunchingGateway jobLaunchingGateway() {
        SimpleJobLauncher simpleJobLauncher = new SimpleJobLauncher();
        simpleJobLauncher.setJobRepository(jobRepository);
        simpleJobLauncher.setTaskExecutor(new SyncTaskExecutor());
        JobLaunchingGateway jobLaunchingGateway = new JobLaunchingGateway(simpleJobLauncher);

        return jobLaunchingGateway;
    }

    @Bean
    public IntegrationFlow integrationFlow(JobLaunchingGateway jobLaunchingGateway) {
        return IntegrationFlows.from(Files.inboundAdapter(new File("/tmp/myfiles")).
                        filter(new SimplePatternFileListFilter("*.csv")),
                c -> c.poller(Pollers.fixedRate(1000).maxMessagesPerPoll(1))).
                transform(fileMessageToJobRequest()).
                handle(jobLaunchingGateway).
                log(LoggingHandler.Level.WARN, "headers.id + ': ' + payload").
                get();
    }

##### Example ItemReader Configuration

Now that we are polling for files and launching jobs, we need to configure our Spring Batch `ItemReader` (for example) to use the files found at the location defined by the job parameter called "input.file.name", as shown in the following bean configuration:

The following XML example shows the necessary bean configuration:

XML Configuration

    <bean id="itemReader" class="org.springframework.batch.item.file.FlatFileItemReader"
        scope="step">
      <property name="resource" value="file://#{jobParameters['input.file.name']}"/>
        ...
    </bean>

The following Java example shows the necessary bean configuration:

Java Configuration

    @Bean
    @StepScope
    public ItemReader sampleReader(@Value("#{jobParameters[input.file.name]}") String resource) {
    ...
        FlatFileItemReader flatFileItemReader = new FlatFileItemReader();
        flatFileItemReader.setResource(new FileSystemResource(resource));
    ...
        return flatFileItemReader;
    }

The main points of interest in the preceding example are injecting the value of `#{jobParameters['input.file.name']}` as the Resource property value and setting the `ItemReader` bean to have Step scope. Setting the bean to have Step scope takes advantage of the late binding support, which allows access to the `jobParameters` variable.

### Available Attributes of the Job-Launching Gateway

The job-launching gateway has the following attributes that you can set to control a job:

- `id`: Identifies the underlying Spring bean definition, which is an instance of either:

  - `EventDrivenConsumer`

  - `PollingConsumer` (The exact implementation depends on whether the component’s input channel is a `SubscribableChannel` or `PollableChannel`.)

- `auto-startup`: Boolean flag to indicate that the endpoint should start automatically on startup. The default is true.

- `request-channel`: The input `MessageChannel` of this endpoint.

- `reply-channel`: `MessageChannel` to which the resulting `JobExecution` payload is sent.

- `reply-timeout`: Lets you specify how long (in milliseconds) this gateway waits for the reply message to be sent successfully to the reply channel before throwing an exception. This attribute only applies when the channel might block (for example, when using a bounded queue channel that is currently full). Also, keep in mind that, when sending to a `DirectChannel`, the invocation occurs in the sender’s thread. Therefore, the failing of the send operation may be caused by other components further downstream. The `reply-timeout` attribute maps to the `sendTimeout` property of the underlying `MessagingTemplate` instance. If not specified, the attribute defaults to<emphasis>-1</emphasis>, meaning that, by default, the `Gateway` waits indefinitely.

- `job-launcher`: Optional. Accepts a custom `JobLauncher` bean reference. If not specified the adapter re-uses the instance that is registered under the `id` of `jobLauncher`. If no default instance exists, an exception is thrown.

- `order`: Specifies the order of invocation when this endpoint is connected as a subscriber to a `SubscribableChannel`.

### Sub-Elements

When this `Gateway` is receiving messages from a `PollableChannel`, you must either provide a global default `Poller` or provide a `Poller` sub-element to the `Job Launching Gateway`.

The following example shows how to provide a poller in XML:

XML Configuration

    <batch-int:job-launching-gateway request-channel="queueChannel"
        reply-channel="replyChannel" job-launcher="jobLauncher">
      <int:poller fixed-rate="1000">
    </batch-int:job-launching-gateway>

The following example shows how to provide a poller in Java:

Java Configuration

    @Bean
    @ServiceActivator(inputChannel = "queueChannel", poller = @Poller(fixedRate="1000"))
    public JobLaunchingGateway sampleJobLaunchingGateway() {
        JobLaunchingGateway jobLaunchingGateway = new JobLaunchingGateway(jobLauncher());
        jobLaunchingGateway.setOutputChannel(replyChannel());
        return jobLaunchingGateway;
    }

#### Providing Feedback with Informational Messages

As Spring Batch jobs can run for long times, providing progress information is often critical. For example, stake-holders may want to be notified if some or all parts of a batch job have failed. Spring Batch provides support for this information being gathered through:

- Active polling

- Event-driven listeners

When starting a Spring Batch job asynchronously (for example, by using the `Job Launching Gateway`), a `JobExecution` instance is returned. Thus, `JobExecution.getJobId()` can be used to continuously poll for status updates by retrieving updated instances of the `JobExecution` from the `JobRepository` by using the `JobExplorer`. However, this is considered sub-optimal, and an event-driven approach should be preferred.

Therefore, Spring Batch provides listeners, including the three most commonly used listeners:

- `StepListener`

- `ChunkListener`

- `JobExecutionListener`

In the example shown in the following image, a Spring Batch job has been configured with a `StepExecutionListener`. Thus, Spring Integration receives and processes any step before or after events. For example, the received `StepExecution` can be inspected by using a `Router`. Based on the results of that inspection, various things can occur (such as routing a message to a Mail Outbound Channel Adapter), so that an Email notification can be sent out based on some condition.

Figure 2. Handling Informational Messages

The following two-part example shows how a listener is configured to send a message to a `Gateway` for a `StepExecution` events and log its output to a `logging-channel-adapter`.

First, create the notification integration beans.

The following example shows the how to create the notification integration beans in XML:

XML Configuration

    <int:channel id="stepExecutionsChannel"/>

    <int:gateway id="notificationExecutionsListener"
        service-interface="org.springframework.batch.core.StepExecutionListener"
        default-request-channel="stepExecutionsChannel"/>

    <int:logging-channel-adapter channel="stepExecutionsChannel"/>

The following example shows the how to create the notification integration beans in Java:

Java Configuration

    @Bean
    @ServiceActivator(inputChannel = "stepExecutionsChannel")
    public LoggingHandler loggingHandler() {
        LoggingHandler adapter = new LoggingHandler(LoggingHandler.Level.WARN);
        adapter.setLoggerName("TEST_LOGGER");
        adapter.setLogExpressionString("headers.id + ': ' + payload");
        return adapter;
    }

    @MessagingGateway(name = "notificationExecutionsListener", defaultRequestChannel = "stepExecutionsChannel")
    public interface NotificationExecutionListener extends StepExecutionListener {}

| You need to add the `@IntegrationComponentScan` annotation to your configuration.

Second, modify your job to add a step-level listener.

The following example shows the how to add a step-level listener in XML:

XML Configuration

    <job id="importPayments">
        <step id="step1">
            <tasklet ../>
                <chunk ../>
                <listeners>
                    <listener ref="notificationExecutionsListener"/>
                </listeners>
            </tasklet>
            ...
        </step>
    </job>

The following example shows the how to add a step-level listener in Java:

Java Configuration

    public Job importPaymentsJob() {
        return jobBuilderFactory.get("importPayments")
            .start(stepBuilderFactory.get("step1")
                    .chunk(200)
                    .listener(notificationExecutionsListener())
                    ...
    }

#### Asynchronous Processors

Asynchronous Processors help you to scale the processing of items. In the asynchronous processor use case, an `AsyncItemProcessor` serves as a dispatcher, executing the logic of the `ItemProcessor` for an item on a new thread. Once the item completes, the `Future` is passed to the `AsynchItemWriter` to be written.

Therefore, you can increase performance by using asynchronous item processing, basically letting you implement fork-join scenarios. The `AsyncItemWriter` gathers the results and writes back the chunk as soon as all the results become available.

The following example shows how to configuration the `AsyncItemProcessor` in XML:

XML Configuration

    <bean id="processor"
        class="org.springframework.batch.integration.async.AsyncItemProcessor">
      <property name="delegate">
        <bean class="your.ItemProcessor"/>
      </property>
      <property name="taskExecutor">
        <bean class="org.springframework.core.task.SimpleAsyncTaskExecutor"/>
      </property>
    </bean>

The following example shows how to configuration the `AsyncItemProcessor` in XML:

Java Configuration

    @Bean
    public AsyncItemProcessor processor(ItemProcessor itemProcessor, TaskExecutor taskExecutor) {
        AsyncItemProcessor asyncItemProcessor = new AsyncItemProcessor();
        asyncItemProcessor.setTaskExecutor(taskExecutor);
        asyncItemProcessor.setDelegate(itemProcessor);
        return asyncItemProcessor;
    }

The `delegate` property refers to your `ItemProcessor` bean, and the `taskExecutor` property refers to the `TaskExecutor` of your choice.

The following example shows how to configure the `AsyncItemWriter` in XML:

XML Configuration

    <bean id="itemWriter"
        class="org.springframework.batch.integration.async.AsyncItemWriter">
      <property name="delegate">
        <bean id="itemWriter" class="your.ItemWriter"/>
      </property>
    </bean>

The following example shows how to configure the `AsyncItemWriter` in Java:

Java Configuration

    @Bean
    public AsyncItemWriter writer(ItemWriter itemWriter) {
        AsyncItemWriter asyncItemWriter = new AsyncItemWriter();
        asyncItemWriter.setDelegate(itemWriter);
        return asyncItemWriter;
    }

Again, the `delegate` property is actually a reference to your `ItemWriter` bean.

#### Externalizing Batch Process Execution

The integration approaches discussed so far suggest use cases where Spring Integration wraps Spring Batch like an outer-shell. However, Spring Batch can also use Spring Integration internally. Using this approach, Spring Batch users can delegate the processing of items or even chunks to outside processes. This allows you to offload complex processing. Spring Batch Integration provides dedicated support for:

- Remote Chunking

- Remote Partitioning

##### Remote Chunking

Figure 3. Remote Chunking

Taking things one step further, one can also externalize the chunk processing by using the `ChunkMessageChannelItemWriter` (provided by Spring Batch Integration), which sends items out and collects the result. Once sent, Spring Batch continues the process of reading and grouping items, without waiting for the results. Rather, it is the responsibility of the `ChunkMessageChannelItemWriter` to gather the results and integrate them back into the Spring Batch process.

With Spring Integration, you have full control over the concurrency of your processes (for instance, by using a `QueueChannel` instead of a `DirectChannel`). Furthermore, by relying on Spring Integration’s rich collection of Channel Adapters (such as JMS and AMQP), you can distribute chunks of a Batch job to external systems for processing.

A job with a step to be remotely chunked might have a configuration similar to the following in XML:

XML Configuration

    <job id="personJob">
      <step id="step1">
        <tasklet>
          <chunk reader="itemReader" writer="itemWriter" commit-interval="200"/>
        </tasklet>
        ...
      </step>
    </job>

A job with a step to be remotely chunked might have a configuration similar to the following in Java:

Java Configuration

    public Job chunkJob() {
         return jobBuilderFactory.get("personJob")
                 .start(stepBuilderFactory.get("step1")
                         .<Person, Person>chunk(200)
                         .reader(itemReader())
                         .writer(itemWriter())
                         .build())
                 .build();
     }

The `ItemReader` reference points to the bean you want to use for reading data on the manager. The `ItemWriter` reference points to a special `ItemWriter` (called `ChunkMessageChannelItemWriter`), as described above. The processor (if any) is left off the manager configuration, as it is configured on the worker. You should check any additional component properties, such as throttle limits and so on, when implementing your use case.

The following XML configuration provides a basic manager setup:

XML Configuration

    <bean id="connectionFactory" class="org.apache.activemq.ActiveMQConnectionFactory">
      <property name="brokerURL" value="tcp://localhost:61616"/>
    </bean>

    <int-jms:outbound-channel-adapter id="jmsRequests" destination-name="requests"/>

    <bean id="messagingTemplate"
        class="org.springframework.integration.core.MessagingTemplate">
      <property name="defaultChannel" ref="requests"/>
      <property name="receiveTimeout" value="2000"/>
    </bean>

    <bean id="itemWriter"
        class="org.springframework.batch.integration.chunk.ChunkMessageChannelItemWriter"
        scope="step">
      <property name="messagingOperations" ref="messagingTemplate"/>
      <property name="replyChannel" ref="replies"/>
    </bean>

    <int:channel id="replies">
      <int:queue/>
    </int:channel>

    <int-jms:message-driven-channel-adapter id="jmsReplies"
        destination-name="replies"
        channel="replies"/>

The following Java configuration provides a basic manager setup:

Java Configuration

    @Bean
    public org.apache.activemq.ActiveMQConnectionFactory connectionFactory() {
        ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory();
        factory.setBrokerURL("tcp://localhost:61616");
        return factory;
    }

    /*
     * Configure outbound flow (requests going to workers)
     */
    @Bean
    public DirectChannel requests() {
        return new DirectChannel();
    }

    @Bean
    public IntegrationFlow outboundFlow(ActiveMQConnectionFactory connectionFactory) {
        return IntegrationFlows
                .from(requests())
                .handle(Jms.outboundAdapter(connectionFactory).destination("requests"))
                .get();
    }

    /*
     * Configure inbound flow (replies coming from workers)
     */
    @Bean
    public QueueChannel replies() {
        return new QueueChannel();
    }

    @Bean
    public IntegrationFlow inboundFlow(ActiveMQConnectionFactory connectionFactory) {
        return IntegrationFlows
                .from(Jms.messageDrivenChannelAdapter(connectionFactory).destination("replies"))
                .channel(replies())
                .get();
    }

    /*
     * Configure the ChunkMessageChannelItemWriter
     */
    @Bean
    public ItemWriter<Integer> itemWriter() {
        MessagingTemplate messagingTemplate = new MessagingTemplate();
        messagingTemplate.setDefaultChannel(requests());
        messagingTemplate.setReceiveTimeout(2000);
        ChunkMessageChannelItemWriter<Integer> chunkMessageChannelItemWriter
                = new ChunkMessageChannelItemWriter<>();
        chunkMessageChannelItemWriter.setMessagingOperations(messagingTemplate);
        chunkMessageChannelItemWriter.setReplyChannel(replies());
        return chunkMessageChannelItemWriter;
    }

The preceding configuration provides us with a number of beans. We configure our messaging middleware using ActiveMQ and the inbound/outbound JMS adapters provided by Spring Integration. As shown, our `itemWriter` bean, which is referenced by our job step, uses the `ChunkMessageChannelItemWriter` for writing chunks over the configured middleware.

Now we can move on to the worker configuration, as shown in the following example:

The following example shows the worker configuration in XML:

XML Configuration

    <bean id="connectionFactory" class="org.apache.activemq.ActiveMQConnectionFactory">
      <property name="brokerURL" value="tcp://localhost:61616"/>
    </bean>

    <int:channel id="requests"/>
    <int:channel id="replies"/>

    <int-jms:message-driven-channel-adapter id="incomingRequests"
        destination-name="requests"
        channel="requests"/>

    <int-jms:outbound-channel-adapter id="outgoingReplies"
        destination-name="replies"
        channel="replies">
    </int-jms:outbound-channel-adapter>

    <int:service-activator id="serviceActivator"
        input-channel="requests"
        output-channel="replies"
        ref="chunkProcessorChunkHandler"
        method="handleChunk"/>

    <bean id="chunkProcessorChunkHandler"
        class="org.springframework.batch.integration.chunk.ChunkProcessorChunkHandler">
      <property name="chunkProcessor">
        <bean class="org.springframework.batch.core.step.item.SimpleChunkProcessor">
          <property name="itemWriter">
            <bean class="io.spring.sbi.PersonItemWriter"/>
          </property>
          <property name="itemProcessor">
            <bean class="io.spring.sbi.PersonItemProcessor"/>
          </property>
        </bean>
      </property>
    </bean>

The following example shows the worker configuration in Java:

Java Configuration

    @Bean
    public org.apache.activemq.ActiveMQConnectionFactory connectionFactory() {
        ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory();
        factory.setBrokerURL("tcp://localhost:61616");
        return factory;
    }

    /*
     * Configure inbound flow (requests coming from the manager)
     */
    @Bean
    public DirectChannel requests() {
        return new DirectChannel();
    }

    @Bean
    public IntegrationFlow inboundFlow(ActiveMQConnectionFactory connectionFactory) {
        return IntegrationFlows
                .from(Jms.messageDrivenChannelAdapter(connectionFactory).destination("requests"))
                .channel(requests())
                .get();
    }

    /*
     * Configure outbound flow (replies going to the manager)
     */
    @Bean
    public DirectChannel replies() {
        return new DirectChannel();
    }

    @Bean
    public IntegrationFlow outboundFlow(ActiveMQConnectionFactory connectionFactory) {
        return IntegrationFlows
                .from(replies())
                .handle(Jms.outboundAdapter(connectionFactory).destination("replies"))
                .get();
    }

    /*
     * Configure the ChunkProcessorChunkHandler
     */
    @Bean
    @ServiceActivator(inputChannel = "requests", outputChannel = "replies")
    public ChunkProcessorChunkHandler<Integer> chunkProcessorChunkHandler() {
        ChunkProcessor<Integer> chunkProcessor
                = new SimpleChunkProcessor<>(itemProcessor(), itemWriter());
        ChunkProcessorChunkHandler<Integer> chunkProcessorChunkHandler
                = new ChunkProcessorChunkHandler<>();
        chunkProcessorChunkHandler.setChunkProcessor(chunkProcessor);
        return chunkProcessorChunkHandler;
    }

Most of these configuration items should look familiar from the manager configuration. Workers do not need access to the Spring Batch `JobRepository` nor to the actual job configuration file. The main bean of interest is the `chunkProcessorChunkHandler`. The `chunkProcessor` property of `ChunkProcessorChunkHandler` takes a configured `SimpleChunkProcessor`, which is where you would provide a reference to your `ItemWriter` (and, optionally, your `ItemProcessor`) that will run on the worker when it receives chunks from the manager.

For more information, see the section of the "Scalability" chapter on Remote Chunking.

Starting from version 4.1, Spring Batch Integration introduces the `@EnableBatchIntegration` annotation that can be used to simplify a remote chunking setup. This annotation provides two beans that can be autowired in the application context:

- `RemoteChunkingManagerStepBuilderFactory`: used to configure the manager step

- `RemoteChunkingWorkerBuilder`: used to configure the remote worker integration flow

These APIs take care of configuring a number of components as described in the following diagram:

Figure 4. Remote Chunking Configuration

On the manager side, the `RemoteChunkingManagerStepBuilderFactory` lets you configure a manager step by declaring:

- the item reader to read items and send them to workers

- the output channel ("Outgoing requests") to send requests to workers

- the input channel ("Incoming replies") to receive replies from workers

A `ChunkMessageChannelItemWriter` and the `MessagingTemplate` are not needed to be explicitly configured (Those can still be explicitly configured if required).

On the worker side, the `RemoteChunkingWorkerBuilder` allows you to configure a worker to:

- listen to requests sent by the manager on the input channel ("Incoming requests")

- call the `handleChunk` method of `ChunkProcessorChunkHandler` for each request with the configured `ItemProcessor` and `ItemWriter`

- send replies on the output channel ("Outgoing replies") to the manager

There is no need to explicitly configure the `SimpleChunkProcessor` and the `ChunkProcessorChunkHandler` (Those can be explicitly configured if required).

The following example shows how to use these APIs:

    @EnableBatchIntegration
    @EnableBatchProcessing
    public class RemoteChunkingJobConfiguration {

        @Configuration
        public static class ManagerConfiguration {

            @Autowired
            private RemoteChunkingManagerStepBuilderFactory managerStepBuilderFactory;

            @Bean
            public TaskletStep managerStep() {
                return this.managerStepBuilderFactory.get("managerStep")
                           .chunk(100)
                           .reader(itemReader())
                           .outputChannel(requests()) // requests sent to workers
                           .inputChannel(replies())   // replies received from workers
                           .build();
            }

            // Middleware beans setup omitted

        }

        @Configuration
        public static class WorkerConfiguration {

            @Autowired
            private RemoteChunkingWorkerBuilder workerBuilder;

            @Bean
            public IntegrationFlow workerFlow() {
                return this.workerBuilder
                           .itemProcessor(itemProcessor())
                           .itemWriter(itemWriter())
                           .inputChannel(requests()) // requests received from the manager
                           .outputChannel(replies()) // replies sent to the manager
                           .build();
            }

            // Middleware beans setup omitted

        }

    }

You can find a complete example of a remote chunking job here.

##### Remote Partitioning

Figure 5. Remote Partitioning

Remote Partitioning, on the other hand, is useful when it is not the processing of items but rather the associated I/O that causes the bottleneck. Using Remote Partitioning, work can be farmed out to workers that execute complete Spring Batch steps. Thus, each worker has its own `ItemReader`, `ItemProcessor`, and `ItemWriter`. For this purpose, Spring Batch Integration provides the `MessageChannelPartitionHandler`.

This implementation of the `PartitionHandler` interface uses `MessageChannel` instances to send instructions to remote workers and receive their responses. This provides a nice abstraction from the transports (such as JMS and AMQP) being used to communicate with the remote workers.

The section of the "Scalability" chapter that addresses remote partitioning provides an overview of the concepts and components needed to configure remote partitioning and shows an example of using the default `TaskExecutorPartitionHandler` to partition in separate local threads of execution. For remote partitioning to multiple JVMs, two additional components are required:

- A remoting fabric or grid environment

- A `PartitionHandler` implementation that supports the desired remoting fabric or grid environment

Similar to remote chunking, JMS can be used as the “remoting fabric”. In that case, use a `MessageChannelPartitionHandler` instance as the `PartitionHandler` implementation, as described earlier.

The following example assumes an existing partitioned job and focuses on the `MessageChannelPartitionHandler` and JMS configuration in XML:

XML Configuration

    <bean id="partitionHandler"
       class="org.springframework.batch.integration.partition.MessageChannelPartitionHandler">
      <property name="stepName" value="step1"/>
      <property name="gridSize" value="3"/>
      <property name="replyChannel" ref="outbound-replies"/>
      <property name="messagingOperations">
        <bean class="org.springframework.integration.core.MessagingTemplate">
          <property name="defaultChannel" ref="outbound-requests"/>
          <property name="receiveTimeout" value="100000"/>
        </bean>
      </property>
    </bean>

    <int:channel id="outbound-requests"/>
    <int-jms:outbound-channel-adapter destination="requestsQueue"
        channel="outbound-requests"/>

    <int:channel id="inbound-requests"/>
    <int-jms:message-driven-channel-adapter destination="requestsQueue"
        channel="inbound-requests"/>

    <bean id="stepExecutionRequestHandler"
        class="org.springframework.batch.integration.partition.StepExecutionRequestHandler">
      <property name="jobExplorer" ref="jobExplorer"/>
      <property name="stepLocator" ref="stepLocator"/>
    </bean>

    <int:service-activator ref="stepExecutionRequestHandler" input-channel="inbound-requests"
        output-channel="outbound-staging"/>

    <int:channel id="outbound-staging"/>
    <int-jms:outbound-channel-adapter destination="stagingQueue"
        channel="outbound-staging"/>

    <int:channel id="inbound-staging"/>
    <int-jms:message-driven-channel-adapter destination="stagingQueue"
        channel="inbound-staging"/>

    <int:aggregator ref="partitionHandler" input-channel="inbound-staging"
        output-channel="outbound-replies"/>

    <int:channel id="outbound-replies">
      <int:queue/>
    </int:channel>

    <bean id="stepLocator"
        class="org.springframework.batch.integration.partition.BeanFactoryStepLocator" />

The following example assumes an existing partitioned job and focuses on the `MessageChannelPartitionHandler` and JMS configuration in Java:

Java Configuration

    /*
     * Configuration of the manager side
     */
    @Bean
    public PartitionHandler partitionHandler() {
        MessageChannelPartitionHandler partitionHandler = new MessageChannelPartitionHandler();
        partitionHandler.setStepName("step1");
        partitionHandler.setGridSize(3);
        partitionHandler.setReplyChannel(outboundReplies());
        MessagingTemplate template = new MessagingTemplate();
        template.setDefaultChannel(outboundRequests());
        template.setReceiveTimeout(100000);
        partitionHandler.setMessagingOperations(template);
        return partitionHandler;
    }

    @Bean
    public QueueChannel outboundReplies() {
        return new QueueChannel();
    }

    @Bean
    public DirectChannel outboundRequests() {
        return new DirectChannel();
    }

    @Bean
    public IntegrationFlow outboundJmsRequests() {
        return IntegrationFlows.from("outboundRequests")
                .handle(Jms.outboundGateway(connectionFactory())
                        .requestDestination("requestsQueue"))
                .get();
    }

    @Bean
    @ServiceActivator(inputChannel = "inboundStaging")
    public AggregatorFactoryBean partitioningMessageHandler() throws Exception {
        AggregatorFactoryBean aggregatorFactoryBean = new AggregatorFactoryBean();
        aggregatorFactoryBean.setProcessorBean(partitionHandler());
        aggregatorFactoryBean.setOutputChannel(outboundReplies());
        // configure other propeties of the aggregatorFactoryBean
        return aggregatorFactoryBean;
    }

    @Bean
    public DirectChannel inboundStaging() {
        return new DirectChannel();
    }

    @Bean
    public IntegrationFlow inboundJmsStaging() {
        return IntegrationFlows
                .from(Jms.messageDrivenChannelAdapter(connectionFactory())
                        .configureListenerContainer(c -> c.subscriptionDurable(false))
                        .destination("stagingQueue"))
                .channel(inboundStaging())
                .get();
    }

    /*
     * Configuration of the worker side
     */
    @Bean
    public StepExecutionRequestHandler stepExecutionRequestHandler() {
        StepExecutionRequestHandler stepExecutionRequestHandler = new StepExecutionRequestHandler();
        stepExecutionRequestHandler.setJobExplorer(jobExplorer);
        stepExecutionRequestHandler.setStepLocator(stepLocator());
        return stepExecutionRequestHandler;
    }

    @Bean
    @ServiceActivator(inputChannel = "inboundRequests", outputChannel = "outboundStaging")
    public StepExecutionRequestHandler serviceActivator() throws Exception {
        return stepExecutionRequestHandler();
    }

    @Bean
    public DirectChannel inboundRequests() {
        return new DirectChannel();
    }

    public IntegrationFlow inboundJmsRequests() {
        return IntegrationFlows
                .from(Jms.messageDrivenChannelAdapter(connectionFactory())
                        .configureListenerContainer(c -> c.subscriptionDurable(false))
                        .destination("requestsQueue"))
                .channel(inboundRequests())
                .get();
    }

    @Bean
    public DirectChannel outboundStaging() {
        return new DirectChannel();
    }

    @Bean
    public IntegrationFlow outboundJmsStaging() {
        return IntegrationFlows.from("outboundStaging")
                .handle(Jms.outboundGateway(connectionFactory())
                        .requestDestination("stagingQueue"))
                .get();
    }

You must also ensure that the partition `handler` attribute maps to the `partitionHandler` bean.

The following example maps the partition `handler` attribute to the `partitionHandler` in XML:

XML Configuration

    <job id="personJob">
      <step id="step1.manager">
        <partition partitioner="partitioner" handler="partitionHandler"/>
        ...
      </step>
    </job>

The following example maps the partition `handler` attribute to the `partitionHandler` in Java:

Java Configuration

    	public Job personJob() {
    		return jobBuilderFactory.get("personJob")
    				.start(stepBuilderFactory.get("step1.manager")
    						.partitioner("step1.worker", partitioner())
    						.partitionHandler(partitionHandler())
    						.build())
    				.build();
    	}

You can find a complete example of a remote partitioning job here.

The `@EnableBatchIntegration` annotation that can be used to simplify a remote partitioning setup. This annotation provides two beans useful for remote partitioning:

- `RemotePartitioningManagerStepBuilderFactory`: used to configure the manager step

- `RemotePartitioningWorkerStepBuilderFactory`: used to configure the worker step

These APIs take care of configuring a number of components as described in the following diagram:

Figure 6. Remote Partitioning Configuration (with job repository polling)
Figure 7. Remote Partitioning Configuration (with replies aggregation)

On the manager side, the `RemotePartitioningManagerStepBuilderFactory` allows you to configure a manager step by declaring:

- the `Partitioner` used to partition data

- the output channel ("Outgoing requests") to send requests to workers

- the input channel ("Incoming replies") to receive replies from workers (when configuring replies aggregation)

- the poll interval and timeout parameters (when configuring job repository polling)

The `MessageChannelPartitionHandler` and the `MessagingTemplate` are not needed to be explicitly configured (Those can still be explicitly configured if required).

On the worker side, the `RemotePartitioningWorkerStepBuilderFactory` allows you to configure a worker to:

- listen to requests sent by the manager on the input channel ("Incoming requests")

- call the `handle` method of `StepExecutionRequestHandler` for each request

- send replies on the output channel ("Outgoing replies") to the manager

There is no need to explicitly configure the `StepExecutionRequestHandler` (which can be explicitly configured if required).

The following example shows how to use these APIs:

    @Configuration
    @EnableBatchProcessing
    @EnableBatchIntegration
    public class RemotePartitioningJobConfiguration {

        @Configuration
        public static class ManagerConfiguration {

            @Autowired
            private RemotePartitioningManagerStepBuilderFactory managerStepBuilderFactory;

            @Bean
            public Step managerStep() {
                     return this.managerStepBuilderFactory
                        .get("managerStep")
                        .partitioner("workerStep", partitioner())
                        .gridSize(10)
                        .outputChannel(outgoingRequestsToWorkers())
                        .inputChannel(incomingRepliesFromWorkers())
                        .build();
            }

            // Middleware beans setup omitted

        }

        @Configuration
        public static class WorkerConfiguration {

            @Autowired
            private RemotePartitioningWorkerStepBuilderFactory workerStepBuilderFactory;

            @Bean
            public Step workerStep() {
                     return this.workerStepBuilderFactory
                        .get("workerStep")
                        .inputChannel(incomingRequestsFromManager())
                        .outputChannel(outgoingRepliesToManager())
                        .chunk(100)
                        .reader(itemReader())
                        .processor(itemProcessor())
                        .writer(itemWriter())
                        .build();
            }

            // Middleware beans setup omitted

        }

    }