JsonItemReader Spring Batch Example

March 26, 2022

In this tutorial, we will see JsonItemReader Spring Batch Example. We will see how to read JSON file in the spring batch using JsonItemReader class and store it in the MySql database. The JsonItemReader class uses JsonObjectReader.

Note – The JsonItemReader implementation is not thread safe. It supports the below format.

[ { JSON object }, { JSON object } ]

Consider we have the following JSON file in the resource directory.

[{
  "id": 1,
  "name": "John",
  "rollNumber": "0126CS090"
}, {
  "id": 2,
  "name": "Arya",
  "rollNumber": "0126CS090"
}, {
  "id": 3,
  "name": "Will",
  "rollNumber": "0126CS090"
}, {
  "id": 4,
  "name": "Smith",
  "rollNumber": "0126CS090"
}, {
  "id": 5,
  "name": "Rock",
  "rollNumber": "0126CS090"
}]

We will read these JSON records using JsonItemReader and store them in the MySql database.

Configuring JsonItemReader.

    public JsonItemReader<Student> jsonItemReader() {
        return new JsonItemReaderBuilder<Student>()
                .jsonObjectReader(new JacksonJsonObjectReader<>(Student.class))
                .resource(new ClassPathResource("data.json"))
                .name("studentJsonItemReader")
                .build();
    }

Let’s see Spring Batch JsonItemReader Example from scratch.

Maven dependency

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.javatute.com</groupId>
    <artifactId>springbatchjsonitemreader</artifactId>
    <version>1.0-SNAPSHOT</version>
    <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>
    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

</project>

Directory structure

Define Student.java

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;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getRollNumber() {
        return rollNumber;
    }

    public void setRollNumber(String rollNumber) {
        this.rollNumber = rollNumber;
    }

}

Define StudentItemProcessor

import com.springbatchexample.entity.Student;
import org.springframework.batch.item.ItemProcessor;

public class StudentItemProcessor implements ItemProcessor<Student, Student> {

    @Override
    public Student process(Student student) throws Exception {
        return student;
    }
}

The StudentItemProcessor can be used to perform any transformations or validation that we need on an item(i.e student) before Spring Batch sends it to the ItemWriter. we are not performing transformations or validation for item.

Define SpringBatchConfig file

package com.springbatchexample.config;

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.BeanPropertyItemSqlParameterSourceProvider;
import org.springframework.batch.item.database.JdbcBatchItemWriter;
import org.springframework.batch.item.file.FlatFileItemReader;
import org.springframework.batch.item.file.LineMapper;
import org.springframework.batch.item.file.mapping.BeanWrapperFieldSetMapper;
import org.springframework.batch.item.file.mapping.DefaultLineMapper;
import org.springframework.batch.item.file.transform.DelimitedLineTokenizer;
import org.springframework.batch.item.json.JacksonJsonObjectReader;
import org.springframework.batch.item.json.JsonItemReader;
import org.springframework.batch.item.json.builder.JsonItemReaderBuilder;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.ClassPathResource;

import javax.sql.DataSource;

@EnableBatchProcessing
@Configuration
public class SpringBatchConfig {


    @Autowired
    private DataSource dataSource;

    @Autowired
    private JobBuilderFactory jobBuilderFactory;

    @Autowired
    private StepBuilderFactory stepBuilderFactory;

    public JsonItemReader<Student> jsonItemReader() {
        return new JsonItemReaderBuilder<Student>()
                .jsonObjectReader(new JacksonJsonObjectReader<>(Student.class))
                .resource(new ClassPathResource("data.json"))
                .name("studentJsonItemReader")
                .build();
    }

    @Bean
    public StudentItemProcessor processor() {
        return new StudentItemProcessor();
    }

    @Bean
    public JdbcBatchItemWriter<Student> writer() {
        JdbcBatchItemWriter<Student> writer = new JdbcBatchItemWriter<>();
        writer.setItemSqlParameterSourceProvider(new BeanPropertyItemSqlParameterSourceProvider<>());
        writer.setSql("insert into student(id,roll_number,name) values (:id,:rollNumber,:name)");
        writer.setDataSource(dataSource);
        return writer;
    }


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

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

}

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

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);
    }
}

Once we run the application we should be able to see data in the database.