Spring Batch ValidatingItemProcessor Example

By
Rakesh
-

Use case – Consider we are reading thousands of records from the database and writing those in CSV files. We want to perform some validation for items before writing those to the CSV file.

Spring batch provides ValidatingItemProcessor class that can be used to perform validation on items.

The ValidatingItemProcessor class implements ItemProcess which is used to validate input and returns it without any modifications.

It contains the below methods.

public T process(T item)
public void setFilter(boolean filter)
public void afterPropertiesSet()
public void setValidator(Validator<? super T> validator)

Define Validator class i.e StudentValidator.java

In this example, we are going to perform very basic validation. If records from the database don’t contain an id or name throw a validation exception.

package com.springbatchexample.component;

import com.springbatchexample.entity.Student;
import org.springframework.batch.item.validator.ValidationException;
import org.springframework.batch.item.validator.Validator;

public class StudentValidator implements Validator<Student> {

    @Override
    public void validate(Student student) throws ValidationException {

        if (student.getId() == null) {

            throw new ValidationException("id must not be null");
        }
        if (student.getName() == null) {
            throw new ValidationException("name must not be null");
        }
    }
}

Configure ValidatingItemProcessor class

    @Bean
    public ValidatingItemProcessor<Student> itemProcessor() {
        ValidatingItemProcessor<Student> validatingItemProcessor = new ValidatingItemProcessor<>();
        validatingItemProcessor.setValidator(new StudentValidator());
        validatingItemProcessor.setFilter(true);
        return validatingItemProcessor;
    }

Call this ValidatingItemProcessor.

    @Bean
    public Step getDbToCsvStep() {
        StepBuilder stepBuilder = stepBuilderFactory.get("getDbToCsvStep");
        SimpleStepBuilder<Student, Student> simpleStepBuilder = stepBuilder.chunk(1);
        return simpleStepBuilder.reader(reader()).processor(itemProcessor()).writer(writer()).build();
    }

We need to call ValidatingItemProcessor using reader.processor() method.

Let’s see the complete Spring Batch ValidatingItemProcessor Example using Spring boot

maven dependency

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.1.RELEASE</version>
    </parent>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.batch</groupId>
            <artifactId>spring-batch-core</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-batch</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
    </dependencies>

package structure

Spring Batch ValidatingItemProcessor example

Model class

package com.springbatchexample.entity;

public class Student {

    private Long id;
    private String name;
    private String rollNumber;
    public Student() {

    }
    public Student(Long id, String name, String rollNumber) {
        this.id = id;
        this.name = name;
        this.rollNumber = rollNumber;
    }
    //getter & setter
}

Define RowMapper

package com.springbatchexample.component;

import com.springbatchexample.entity.Student;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.stereotype.Component;

import java.sql.ResultSet;
import java.sql.SQLException;

@Component
public class StudentResultRowMapper implements RowMapper<Student> {
    @Override
    public Student mapRow(ResultSet rs, int i) throws SQLException {
        Student student = new Student();
        student.setId(rs.getLong("id"));
        student.setRollNumber(rs.getString("roll_number"));
        student.setName(rs.getString("name"));
        return student;
    }
}

This StudentResultRowMapper will get used while creating reader using JdbcCursorItemReader.

Define SpringBatchConfig file

package com.springbatchexample.config;

import com.springbatchexample.component.StudentResultRowMapper;
import com.springbatchexample.component.StudentValidator;
import com.springbatchexample.entity.Student;
import org.springframework.batch.core.Job;
import org.springframework.batch.core.Step;
import org.springframework.batch.core.configuration.annotation.EnableBatchProcessing;
import org.springframework.batch.core.configuration.annotation.JobBuilderFactory;
import org.springframework.batch.core.configuration.annotation.StepBuilderFactory;
import org.springframework.batch.core.job.builder.FlowJobBuilder;
import org.springframework.batch.core.job.builder.JobBuilder;
import org.springframework.batch.core.launch.support.RunIdIncrementer;
import org.springframework.batch.core.step.builder.SimpleStepBuilder;
import org.springframework.batch.core.step.builder.StepBuilder;
import org.springframework.batch.item.database.JdbcCursorItemReader;
import org.springframework.batch.item.file.FlatFileItemWriter;
import org.springframework.batch.item.file.transform.BeanWrapperFieldExtractor;
import org.springframework.batch.item.file.transform.DelimitedLineAggregator;
import org.springframework.batch.item.validator.ValidatingItemProcessor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.FileSystemResource;

import javax.sql.DataSource;

@EnableBatchProcessing
@Configuration
public class SpringBatchConfig {


    @Autowired
    private DataSource dataSource;

    @Autowired
    private JobBuilderFactory jobBuilderFactory;

    @Autowired
    private StepBuilderFactory stepBuilderFactory;


    @Bean
    public JdbcCursorItemReader<Student> reader() {
        JdbcCursorItemReader<Student> reader = new JdbcCursorItemReader<>();
        reader.setDataSource(dataSource);
        reader.setSql("select id, roll_number, name from student");
        reader.setRowMapper(new StudentResultRowMapper());
        return reader;
    }

    @Bean
    public FlatFileItemWriter<Student> writer() {
        FlatFileItemWriter<Student> writer = new FlatFileItemWriter<>();
        writer.setResource(new FileSystemResource("C://data/batch/data.csv"));
        writer.setLineAggregator(getDelimitedLineAggregator());
        return writer;
    }

    private DelimitedLineAggregator<Student> getDelimitedLineAggregator() {
        BeanWrapperFieldExtractor<Student> beanWrapperFieldExtractor = new BeanWrapperFieldExtractor<Student>();
        beanWrapperFieldExtractor.setNames(new String[]{"id", "rollNumber", "name"});

        DelimitedLineAggregator<Student> aggregator = new DelimitedLineAggregator<Student>();
        aggregator.setDelimiter(",");
        aggregator.setFieldExtractor(beanWrapperFieldExtractor);
        return aggregator;

    }

    @Bean
    public Step getDbToCsvStep() {
        StepBuilder stepBuilder = stepBuilderFactory.get("getDbToCsvStep");
        SimpleStepBuilder<Student, Student> simpleStepBuilder = stepBuilder.chunk(1);
        return simpleStepBuilder.reader(reader()).processor(itemProcessor()).writer(writer()).build();
    }

    @Bean
    public Job dbToCsvJob() {
        JobBuilder jobBuilder = jobBuilderFactory.get("dbToCsvJob");
        jobBuilder.incrementer(new RunIdIncrementer());
        FlowJobBuilder flowJobBuilder = jobBuilder.flow(getDbToCsvStep()).end();
        Job job = flowJobBuilder.build();
        return job;
    }

    @Bean
    public ValidatingItemProcessor<Student> itemProcessor() {
        ValidatingItemProcessor<Student> validatingItemProcessor = new ValidatingItemProcessor<>();
        validatingItemProcessor.setValidator(new StudentValidator());
        validatingItemProcessor.setFilter(true);
        return validatingItemProcessor;
    }
}

Define SpringMain class

package com.springbatchexample.main;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;

@SpringBootApplication
@ComponentScan(basePackages = "com.springbatchexample.*")
public class SpringMain {
    public static void main(String[] args) {

        SpringApplication.run(SpringMain.class, args);
    }
}

application.properties

spring.datasource.url=jdbc:mysql://localhost:3306/springbootcrudexample
spring.datasource.username=root
spring.datasource.password=root
spring.jpa.hibernate.ddl-auto=create
spring.jpa.show-sql=true
spring.jpa.properties.hibernate.format_sql=true
server.port = 9091
spring.batch.initialize-schema=always

Note – For more details about the ValidatingItemProcessor spring batch see docs.

Other Spring Batch Tutorials.

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