Despite the relatively short list of required dependencies for a Step, it is an extremely complex class that can potentially contain many collaborators. In order to ease configuration, the Spring Batch namespace can be used:

<job id="sampleJob" job-repository="jobRepository">
    <step id="step1">
        <tasklet transaction-manager="transactionManager">
            <chunk reader="itemReader" writer="itemWriter" commit-interval="10"/>
        </tasklet>
    </step>
</job>

The configuration above represents the only required dependencies to create a item-oriented step:

It should be noted that, job-repository defaults to "jobRepository" and transaction-manager defaults to "transactionManger". Furthermore, the ItemProcessor is optional, not required, since the item could be directly passed from the reader to the writer.

If a group of Steps share similar configurations, then it may be helpful to define a "parent" Step from which the concrete Steps may inherit properties. Similar to class inheritance in Java, the "child" Step will combine its elements and attributes with the parent's. The child will also override any of the parent's Steps.

In the following example, the Step "concreteStep1" will inherit from "parentStep". It will be instantiated with 'itemReader', 'itemProcessor', 'itemWriter', startLimit=5, and allowStartIfComplete=true. Additionally, the commitInterval will be '5' since it is overridden by the "concreteStep1":

<step id="parentStep">
    <tasklet allow-start-if-complete="true">
        <chunk reader="itemReader" writer="itemWriter" commit-interval="10"/>
    </tasklet>
</step>

<step id="concreteStep1" parent="parentStep">
    <tasklet start-limit="5">
        <chunk processor="itemProcessor" commit-interval="5"/>
    </tasklet>
</step>

The id attribute is still required on the step within the job element. This is for two reasons:

<step id="abstractParentStep" abstract="true">
    <tasklet>
        <chunk commit-interval="10"/>
    </tasklet>
</step>

<step id="concreteStep2" parent="abstractParentStep">
    <tasklet>
        <chunk reader="itemReader" writer="itemWriter"/>
    </tasklet>
</step>

<step id="listenersParentStep" abstract="true">
    <listeners>
        <listener ref="listenerOne"/>
    <listeners>
</step>

<step id="concreteStep3" parent="listenersParentStep">
    <tasklet>
        <chunk reader="itemReader" writer="itemWriter" commit-interval="5"/>
    </tasklet>
    <listeners merge="true">
        <listener ref="listenerTwo"/>
    <listeners>
</step>

As mentioned above, a step reads in and writes out items, periodically committing using the supplied PlatformTransactionManager. With a commit-interval of 1, it will commit after writing each individual item. This is less than ideal in many situations, since beginning and committing a transaction is expensive. Ideally, it is preferable to process as many items as possible in each transaction, which is completely dependent upon the type of data being processed and the resources with which the step is interacting. For this reason, the number of items that are processed within a commit can be configured.

<job id="sampleJob">
    <step id="step1">
        <tasklet>
            <chunk reader="itemReader" writer="itemWriter" commit-interval="10"/>
        </tasklet>
    </step>
</job>

In the example above, 10 items will be processed within each transaction. At the beginning of processing a transaction is begun, and each time read is called on the ItemReader, a counter is incremented. When it reaches 10, the list of aggregated items is passed to the ItemWriter, and the transaction will be committed.

In Chapter 4, Configuring and Running a Job, restarting a Job was discussed. Restart has numerous impacts on steps, and as such may require some specific configuration.

<step id="step1">
    <tasklet start-limit="1">
        <chunk reader="itemReader" writer="itemWriter" commit-interval="10"/>
    </tasklet>
</step>

<step id="step1">
    <tasklet allow-start-if-complete="true">
        <chunk reader="itemReader" writer="itemWriter" commit-interval="10"/>
    </tasklet>
</step>

<job id="footballJob" restartable="true">
    <step id="playerload" next="gameLoad">
        <tasklet>
            <chunk reader="playerFileItemReader" writer="playerWriter" 
                   commit-interval="10" />
        </tasklet>
    </step>
    <step id="gameLoad" next="playerSummarization">
        <tasklet allow-start-if-complete="true">
            <chunk reader="gameFileItemReader" writer="gameWriter" 
                   commit-interval="10"/>
        </tasklet>
    </step>
    <step id="playerSummarization">
        <tasklet start-limit="3">
            <chunk reader="playerSummarizationSource" writer="summaryWriter" 
                   commit-interval="10"/>
        </tasklet>
    </step>
</job>

There are many scenarios where errors encountered while processing should not result in Step failure, but should be skipped instead. This is usually a decision that must be made by someone who understands the data itself and what meaning it has. Financial data, for example, may not be skippable because it results in money being transferred, which needs to be completely accurate. Loading a list of vendors, on the other hand, might allow for skips. If a vendor is not loaded because it was formatted incorrectly or was missing necessary information, then there probably won't be issues. Usually these bad records are logged as well, which will be covered later when discussing listeners.

<step id="step1">
   <tasklet>
      <chunk reader="flatFileItemReader" writer="itemWriter" 
             commit-interval="10" skip-limit="10">
         <skippable-exception-classes>
            <include class="org.springframework.batch.item.file.FlatFileParseException"/>
         </skippable-exception-classes>
      </chunk>
   </tasklet>
</step>

In this example, a FlatFileItemReader is used, and if at any point a FlatFileParseException is thrown, it will be skipped and counted against the total skip limit of 10. Separate counts are made of skips on read, process and write inside the step execution, and the limit applies across all. Once the skip limit is reached, the next exception found will cause the step to fail.

One problem with the example above is that any other exception besides a FlatFileParseException will cause the Job to fail. In certain scenarios this may be the correct behavior. However, in other scenarios it may be easier to identify which exceptions should cause failure and skip everything else:

<step id="step1">
    <tasklet>
        <chunk reader="flatFileItemReader" writer="itemWriter" 
               commit-interval="10" skip-limit="10">
            <skippable-exception-classes>
                <include class="java.lang.Exception"/>
                <exclude class="java.io.FileNotFoundException"/>
            </skippable-exception-classes>
        </chunk>
    </tasklet>
</step>

By 'including' java.lang.Exception as a skippable exception class, the configuration indicates that all Exceptions are skippable. However, by 'excluding' java.io.FileNotFoundException, the configuration refines the list of skippable exception classes to be all Exceptions except FileNotFoundException. Any excluded exception classes will be fatal if encountered (i.e. not skipped).

For any exception encountered, the skippability will be determined by the nearest superclass in the class hierarchy. Any unclassifed exception will be treated as 'fatal'. The order of the <include/> and <exclude/> elements does not matter.

In most cases you want an exception to cause either a skip or Step failure. However, not all exceptions are deterministic. If a FlatFileParseException is encountered while reading, it will always be thrown for that record; resetting the ItemReader will not help. However, for other exceptions, such as a DeadlockLoserDataAccessException, which indicates that the current process has attempted to update a record that another process holds a lock on, waiting and trying again might result in success. In this case, retry should be configured:

<step id="step1">
   <tasklet>
      <chunk reader="itemReader" writer="itemWriter" 
             commit-interval="2" retry-limit="3">
         <retryable-exception-classes>
            <include class="org.springframework.dao.DeadlockLoserDataAccessException"/>
         </retryable-exception-classes>
      </chunk>
   </tasklet>
</step>

The Step allows a limit for the number of times an individual item can be retried, and a list of exceptions that are 'retryable'. More details on how retry works can be found in Chapter 9, Retry.

By default, regardless of retry or skip, any exceptions thrown from the ItemWriter will cause the transaction controlled by the Step to rollback. If skip is configured as described above, exceptions thrown from the ItemReader will not cause a rollback. However, there are many scenarios in which exceptions thrown from the ItemWriter should not cause a rollback because no action has taken place to invalidate the transaction. For this reason, the Step can be configured with a list of exceptions that should not cause rollback.

<step id="step1">
   <tasklet>
      <chunk reader="itemReader" writer="itemWriter" commit-interval="2"/>
      <no-rollback-exception-classes>
         <include class="org.springframework.batch.item.validator.ValidationException"/>
      </no-rollback-exception-classes>
   </tasklet>
</step>

<step id="step1">
    <tasklet>
        <chunk reader="itemReader" writer="itemWriter" commit-interval="2"
               is-reader-transactional-queue="true"/>
    </tasklet>
</step>

Transaction attributes can be used to control the isolation, propagation, and timeout settings. More information on setting transaction attributes can be found in the spring core documentation.

<step id="step1">
    <tasklet>
        <chunk reader="itemReader" writer="itemWriter" commit-interval="2"/>
        <transaction-attributes isolation="DEFAULT" 
                                propagation="REQUIRED" 
                                timeout="30"/>
    </tasklet>
</step>

The step has to take care of ItemStream callbacks at the necessary points in its lifecycle. (for more information on the ItemStream interface, please refer to Section 6.4, “ItemStream”) This is vital if a step fails, and might need to be restarted, because the ItemStream interface is where the step gets the information it needs about persistent state between executions.

If the ItemReader, ItemProcessor, or ItemWriter itself implements the ItemStream interface, then these will be registered automatically. Any other streams need to be registered separately. This is often the case where there are indirect dependencies such as delegates being injected into the reader and writer. A stream can be registered on the Step through the 'streams' element, as illustrated below:

<step id="step1">
    <tasklet>
        <chunk reader="itemReader" writer="compositeWriter" commit-interval="2">
            <streams>
                <stream ref="fileItemWriter1"/>
                <stream ref="fileItemWriter2"/>
            </streams>
        </chunk>
    </tasklet>
</step>

<beans:bean id="compositeWriter" 
            class="org.springframework.batch.item.support.CompositeItemWriter">
    <beans:property name="delegates">
        <beans:list>
            <beans:ref bean="fileItemWriter1" />
            <beans:ref bean="fileItemWriter2" />
        </beans:list>
    </beans:property>
</beans:bean>

In the example above, the CompositeItemWriter is not an ItemStream, but both of its delegates are. Therefore, both delegate writers must be explicitly registered as streams in order for the framework to handle them correctly. The ItemReader does not need to be explicitly registered as a stream because it is a direct property of the Step. The step will now be restartable and the state of the reader and writer will be correctly persisted in the event of a failure.

Just as with the Job, there are many events during the execution of a Step where a user may need to perform some functionality. For example, in order to write out to a flat file that requires a footer, the ItemWriter needs to be notified when the Step has been completed, so that the footer can written. This can be accomplished with one of many Step scoped listeners.

Any class that implements one of the extensions of StepListener (but not that interface itself since it is empty) can be applied to a step via the listeners element. The listeners element is valid inside a step, tasklet or chunk declaration. It is recommended that you declare the listeners at the level which its function applies, or if it is multi-featured (e.g. StepExecutionListener and ItemReadListener) then declare it at the most granular level that it applies (chunk in the example given).

<step id="step1">
    <tasklet>
        <chunk reader="reader" writer="writer" commit-interval="10"/>
        <listeners>
            <listener ref="chunkListener"/>
        </listeners>
    </tasklet>
</step>

An ItemReader, ItemWriter or ItemProcessor that itself implements one of the StepListener interfaces will be registered automatically with the Step if using the namespace <step> element, or one of the the *StepFactoryBean factories. This only applies to components directly injected into the Step: if the listener is nested inside another component, it needs to be explicitly registered (as described above).

In addition to the StepListener interfaces, annotations are provided to address the same concerns. Plain old Java objects can have methods with these annotations that are then converted into the corresponding StepListener type. It is also common to annotate custom implementations of chunk components like ItemReader or ItemWriter or Tasklet. The annotations are analysed by the XML parser for the <listener/> elements, so all you need to do is use the XML namespace to register the listeners with a step.

public interface StepExecutionListener extends StepListener {

    void beforeStep(StepExecution stepExecution);

    ExitStatus afterStep(StepExecution stepExecution);

}

public interface ChunkListener extends StepListener {

    void beforeChunk();

    void afterChunk();

}

public interface ItemReadListener<T> extends StepListener {
  
    void beforeRead();

    void afterRead(T item);
    
    void onReadError(Exception ex);

}

public interface ItemProcessListener<T, S> extends StepListener {

    void beforeProcess(T item);

    void afterProcess(T item, S result);

    void onProcessError(T item, Exception e);

}

  public interface ItemWriteListener<S> extends StepListener {

    void beforeWrite(List<? extends S> items);

    void afterWrite(List<? extends S> items);

    void onWriteError(Exception exception, List<? extends S> items);

}

  public interface SkipListener<T,S> extends StepListener {

    void onSkipInRead(Throwable t);

    void onSkipInProcess(T item, Throwable t);

    void onSkipInWrite(S item, Throwable t);

}

As with other adapters for the ItemReader and ItemWriter interfaces, the Tasklet interface contains an implementation that allows for adapting itself to any pre-existing class: TaskletAdapter. An example where this may be useful is an existing DAO that is used to update a flag on a set of records. The TaskletAdapter can be used to call this class without having to write an adapter for the Tasklet interface:

<bean id="myTasklet" class="org.springframework.batch.core.step.tasklet.MethodInvokingTaskletAdapter">
    <property name="targetObject">
        <bean class="org.mycompany.FooDao"/>
    </property>
    <property name="targetMethod" value="updateFoo" />
</bean>

Many batch jobs contain steps that must be done before the main processing begins in order to set up various resources or after processing has completed to cleanup those resources. In the case of a job that works heavily with files, it is often necessary to delete certain files locally after they have been uploaded successfully to another location. The example below taken from the Spring Batch samples project, is a Tasklet implementation with just such a responsibility:

public class FileDeletingTasklet implements Tasklet, InitializingBean {

    private Resource directory;

    public RepeatStatus execute(StepContribution contribution, 
                                ChunkContext chunkContext) throws Exception {
        File dir = directory.getFile();
        Assert.state(dir.isDirectory());
    
        File[] files = dir.listFiles();
        for (int i = 0; i < files.length; i++) {
            boolean deleted = files[i].delete();
            if (!deleted) {
                throw new UnexpectedJobExecutionException("Could not delete file " + 
                                                          files[i].getPath());
            }
        }
        return RepeatStatus.COMPLETED;
    }

    public void setDirectoryResource(Resource directory) {
        this.directory = directory;
    }

    public void afterPropertiesSet() throws Exception {
        Assert.notNull(directory, "directory must be set");
    }
}

The above Tasklet implementation will delete all files within a given directory. It should be noted that the execute method will only be called once. All that is left is to reference the Tasklet from the Step:

<job id="taskletJob">
    <step id="deleteFilesInDir">
       <tasklet ref="fileDeletingTasklet"/>
    </step>
</job>

<beans:bean id="fileDeletingTasklet" 
            class="org.springframework.batch.sample.tasklet.FileDeletingTasklet">
    <beans:property name="directoryResource">
        <beans:bean id="directory" 
                    class="org.springframework.core.io.FileSystemResource">
            <beans:constructor-arg value="target/test-outputs/test-dir" />
        </beans:bean>
    </beans:property>
</beans:bean>

The simplest flow scenario is a job where all of the steps execute sequentially:

This can be achieved using the 'next' attribute of the step element:

<job id="job">
    <step id="stepA" parent="s1" next="stepB" />
    <step id="stepB" parent="s2" next="stepC"/>
    <step id="stepC" parent="s3" />
</job>

In the scenario above, 'step A' will execute first because it is the first Step listed. If 'step A' completes normally, then 'step B' will execute, and so on. However, if 'step A' fails, then the entire Job will fail and 'step B' will not execute.

In the example above, there are only two possibilities:

In many cases, this may be sufficient. However, what about a scenario in which the failure of a Step should trigger a different Step, rather than causing failure?

In order to handle more complex scenarios, the Spring Batch namespace allows transition elements to be defined within the step element. One such transition is the "next" element. Like the "next" attribute, the "next" element will tell the Job which Step to execute next. However, unlike the attribute, any number of "next" elements are allowed on a given Step, and there is no default behavior the case of failure. This means that if transition elements are used, then all of the behavior for the Step's transitions must be defined explicitly. Note also that a single step cannot have both a "next" attribute and a transition element.

The next element specifies a pattern to match and the step to execute next:

<job id="job">
    <step id="stepA" parent="s1">
        <next on="*" to="stepB" />
        <next on="FAILED" to="stepC" />
    </step>
    <step id="stepB" parent="s2" next="stepC" />
    <step id="stepC" parent="s3" />
</job>

The "on" attribute of a transition element uses a simple pattern-matching scheme to match the ExitStatus that results from the execution of the Step. Only two special characters are allowed in the pattern:

For example, "c*t" will match "cat" and "count", while "c?t" will match "cat" but not "count".

While there is no limit to the number of transition elements on a Step, if the Step's execution results in an ExitStatus that is not covered by an element, then the framework will throw an exception and the Job will fail. The framework will automatically order transitions from most specific to least specific. This means that even if the elements were swapped for "stepA" in the example above, an ExitStatus of "FAILED" would still go to "stepC".

<next on="FAILED" to="stepB" />

<step id="step1" parent="s1">
    <end on="FAILED" />
    <next on="COMPLETED WITH SKIPS" to="errorPrint1" />
    <next on="*" to="step2" />
</step>

public class SkipCheckingListener extends StepExecutionListenerSupport {

    public ExitStatus afterStep(StepExecution stepExecution) {
        String exitCode = stepExecution.getExitStatus().getExitCode();
        if (!exitCode.equals(ExitStatus.FAILED.getExitCode()) && 
              stepExecution.getSkipCount() > 0) {
            return new ExitStatus("COMPLETED WITH SKIPS");
        }
        else {
            return null;
        }
    }

}

After the discussion of BatchStatus and ExitStatus, one might wonder how the BatchStatus and ExitStatus are determined for the Job. While these statuses are determined for the Step by the code that is executed, the statuses for the Job will be determined based on the configuration.

So far, all of the job configurations discussed have had at least one final Step with no transitions. For example, after the following step executes, the Job will end:

<step id="stepC" parent="s3"/>

If no transitions are defined for a Step, then the Job's statuses will be defined as follows:

While this method of terminating a batch job is sufficient for some batch jobs, such as a simple sequential step job, custom defined job-stopping scenarios may be required. For this purpose, Spring Batch provides three transition elements to stop a Job (in addition to the "next" element that we discussed previously). Each of these stopping elements will stop a Job with a particular BatchStatus. It is important to note that the stop transition elements will have no effect on either the BatchStatus or ExitStatus of any Steps in the Job: these elements will only affect the final statuses of the Job. For example, it is possible for every step in a job to have a status of FAILED but the job to have a status of COMPLETED, or vise versa.

<step id="step1" parent="s1" next="step2">

<step id="step2" parent="s2">
    <end on="FAILED"/>
    <next on="*" to="step3"/>
</step>

<step id="step3" parent="s3">

<step id="step1" parent="s1" next="step2">

<step id="step2" parent="s2">
    <fail on="FAILED" exit-code="EARLY TERMINATION"/>
    <next on="*" to="step3"/>
</step>

<step id="step3" parent="s3">

<step id="step1" parent="s1">
    <stop on="COMPLETED" restart="step2"/>
</step>

<step id="step2" parent="s2"/>

In some situations, more information than the ExitStatus may be required to decide which step to execute next. In this case, a JobExecutionDecider can be used to assist in the decision.

public class MyDecider implements JobExecutionDecider {
    public FlowExecutionStatus decide(JobExecution jobExecution, StepExecution stepExecution) {
        if (someCondition) {
            return "FAILED";
        }
        else {
            return "COMPLETED";
        }
    }
}

In the job configuration, a "decision" tag will specify the decider to use as well as all of the transitions.

<job id="job">
    <step id="step1" parent="s1" next="decision" />
    
    <decision id="decision" decider="decider">
        <next on="FAILED" to="step2" />
        <next on="COMPLETED" to="step3" />
    </decision>

    <step id="step2" parent="s2" next="step3"/>
    <step id="step3" parent="s3" />
</job>

<beans:bean id="decider" class="com.MyDecider"/>

Every scenario described so far has involved a Job that executes its Steps one at a time in a linear fashion. In addition to this typical style, the Spring Batch namespace also allows for a job to be configured with parallel flows using the 'split' element. As is seen below, the 'split' element contains one or more 'flow' elements, where entire separate flows can be defined. A 'split' element may also contain any of the previously discussed transition elements such as the 'next' attribute or the 'next', 'end', 'fail', or 'pause' elements.

<split id="split1" next="step4">
    <flow>
        <step id="step1" parent="s1" next="step2"/>
        <step id="step2" parent="s2"/>
    </flow>
    <flow>
        <step id="step3" parent="s3"/>
    </flow>
</split>
<step id="step4" parent="s4"/>

Part of the flow in a job can be externalized as a separate bean definition, and then re-used. There are two ways to do this, and the first is to simply declare the flow as a reference to one defined elsewhere:

<job id="job">
    <flow id="job1.flow1" parent="flow1" next="step3"/>
    <step id="step3" parent="s3"/>
</job>

<flow id="flow1">
    <step id="step1" parent="s1" next="step2"/>
    <step id="step2" parent="s2"/>
</flow>

The effect of defining an external flow like this is simply to insert the steps from the external flow into the job as if they had been declared inline. In this way many jobs can refer to the same template flow and compose such templates into different logical flows. This is also a good way to separate the integration testing of the individual flows.

The other form of an externalized flow is to use a JobStep. A JobStep is similar to a FlowStep, but actually creates and launches a separate job execution for the steps in the flow specified. Here is an example:

<job id="jobStepJob" restartable="true">
   <step id="jobStepJob.step1">
      <job ref="job" job-launcher="jobLauncher" 
          job-parameters-extractor="jobParametersExtractor"/>
   </step>
</job>

<job id="job" restartable="true">...</job>

<bean id="jobParametersExtractor" class="org.spr...DefaultJobParametersExtractor">
   <property name="keys" value="input.file"/>
</bean>

The job parameters extractor is a strategy that determines how a the ExecutionContext for the Step is converted into JobParameters for the Job that is executed. The JobStep is useful when you want to have some more granular options for monitoring and reporting on jobs and steps. Using JobStep is also often a good answer to the question: "How do I create dependencies between jobs?". It is a good way to break up a large system into smaller modules and control the flow of jobs.

All of the late binding examples from above have a scope of "step" declared on the bean definition:

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

Using a scope of Step is required in order to use late binding since the bean cannot actually be instantiated until the Step starts, which allows the attributes to be found. Because it is not part of the Spring container by default, the scope must be added explicitly, either by using the batch namespace:

<beans xmlns="http://www.springframework.org/schema/beans" 
       xmlns:batch="http://www.springframework.org/schema/batch" 
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="...">
<batch:job .../>
...
</beans>

or by including a bean definition explicitly for the StepScope (but not both):

<bean class="org.springframework.batch.core.scope.StepScope" />