4.1.3.2. Create Batch to Derive Data (Chunk Step)¶

4.1.3.2.1.1. Reads data from the input data source¶

Implements the process to fetch the data required for calculation.

1. Create a form
2. Create an ItemReader

Create a form

In the Chunk step, use form to link data with ItemReader and ItemProcessor.

EmployeeForm.java

public class EmployeeForm {

    //Partial excerpt

    /** Employee ID */
    private Long employeeId;

    /**
     *Returns employee ID.
     *
     * @return Employee ID
     */
    public Long getEmployeeId() {
        return employeeId;
    }

    /**
     * Sets the employee ID.
     *
     * @param employeeId Employee ID
     */
    public void setEmployeeId(Long employeeId) {
        this.employeeId = employeeId;
    }
}

Create an ItemReader

Inherits AbstractItemReader and reads data.

Interface Name	Obligation
ItemReader	Reads data. Inherits AbstractItemReader, which provides a empty implementation. ItemReader#open ItemReader#readItem ItemReader#close

EmployeeSearchReader.java

@Dependent
@Named
public class EmployeeSearchReader extends AbstractItemReader {

    /** List of employee information */
    private DeferredEntityList<EmployeeForm> list;

    /** Iterator holding employee information */
    private Iterator<EmployeeForm> iterator;

    @Override
    public void open(Serializable checkpoint) throws Exception {
        list = (DeferredEntityList<EmployeeForm>) UniversalDao.defer()
                .findAllBySqlFile(EmployeeForm.class, "SELECT_EMPLOYEE");
        iterator = list.iterator();
    }

    @Override
    public Object readItem() {
        if (iterator.hasNext()) {
            return iterator.next();
        }
        return null;
    }

    @Override
    public void close() throws Exception {
        list.close();
    }
}

EmployeeForm.sql

SELECT_EMPLOYEE=
SELECT
    EMPLOYEE.EMPLOYEE_ID,
    EMPLOYEE.FULL_NAME,
    EMPLOYEE.BASIC_SALARY,
    EMPLOYEE.GRADE_CODE,
    GRADE.BONUS_MAGNIFICATION,
    GRADE.FIXED_BONUS
FROM
    EMPLOYEE
INNER JOIN GRADE ON EMPLOYEE.GRADE_CODE = GRADE.GRADE_CODE

Key points of this implementation

• Named and Dependent are assigned to the class. For details, see Explanation of named and dependent of batchlet.
• Read the data to be processed with open method.
• For the location and how to create the SQL file, see Search with any SQL (SQL file).
• When reading a large amount of data, to prevent straining of the memory, use UniversalDao#defer to defer the loading of the search results.
• Returns one line of data from the data read by readItem method. The object returned by this method is given as an argument of processItem method of ItemProcessor that follows.

4.1.3.2.1.2. Execute business logic¶

Implements the business logic of bonus calculation.

Create ItemProcessor

Implements ItemProcessor and carries out the business logic (since the persistence process is a duty of ItemWriter, it is not executed).

Interface Name	Obligation
ItemProcessor	Performs the business process on one line of data. ItemProcessor#processItem

BonusCalculateProcessor.java

@Dependent
@Named
public class BonusCalculateProcessor implements ItemProcessor {

    @Override
    public Object processItem(Object item) {

        EmployeeForm form = (EmployeeForm) item;
        Bonus bonus = new Bonus();
        bonus.setEmployeeId(form.getEmployeeId());
        bonus.setPayments(calculateBonus(form));

        return bonus;
    }

    /**
     * Calculate bonus based on employee information.
     *
     * @param form Employee Information Form
     * @return Bonus
     */
    private static Long calculateBonus(EmployeeForm form) {
        if (form.getFixedBonus() == null) {
            return form.getBasicSalary() * form.getBonusMagnification() / 100;
        } else {
            return form.getFixedBonus();
        }
    }
}

Key points of this implementation

• At the timing when a certain number of entities (how to configure is described in Create a configuration file for JOB) are returned by the processItem method, the writeItems method of ItemWriter that follows is executed.

4.1.3.2.1.3. Persistence process¶

Implements the persistence process for DB update, etc.

Create ItemWriter

Implements ItemWriter and makes data persistence.

Interface Name	Obligation
ItemWriter	Persistence of data ItemWriter#writeItems

BonusWriter.java

@Dependent
@Named
public class BonusWriter extends AbstractItemWriter {

    @Override
    public void writeItems(List<Object> items) {
        UniversalDao.batchInsert(items);
    }
}

Key points of this implementation

• Uses UniversalDao#batchInsert to batch register entity list.
• The transaction is committed after execution of the writeItems method and a new transaction is started.
• After execution of the writeItems method, the batch process is repeated from the execution of readItem method.

4.1.3.2.1.4. Create a configuration file for JOB¶

Create a file with the job execution configuration.

bonus-calculate.xml

<job id="bonus-calculate" xmlns="http://xmlns.jcp.org/xml/ns/javaee" version="1.0">
  <listeners>
    <listener ref="nablarchJobListenerExecutor" />
  </listeners>

  <step id="step1">
    <listeners>
      <listener ref="nablarchStepListenerExecutor" />
      <listener ref="nablarchItemWriteListenerExecutor" />
    </listeners>

    <chunk item-count="1000">
      <reader ref="employeeSearchReader" />
      <processor ref="bonusCalculateProcessor" />
      <writer ref="bonusWriter" />
    </chunk>
  </step>
</job>

Key points of this implementation

• The job definition file is located under /src/main/resources/META-INF/batch-jobs/.
• Specify the job name in the id attribute of the job element.
• Configure the number of writeItems processed each time by the item-count attribute of the chunk element.
• Refer to JSR352 specification (external site) for detailed description method of the configuration file.