Introduction

This tutorial will show you how to read a csv file data and write to xml file with some modification. We’ll build a service that imports data from a CSV file, transforms it with custom code, and stores the final results in XML file.

You can read the tutorial Spring Batch to read what is Spring Batch and what are the usages of Spring Batch.

Prerequisites

Eclipse, Gradle 4.10.2, Spring Boot 2.1.4, Java 8

Spring Batch

Example with Source Code

Creating Project

Create gradle based project in Eclipse IDE and you will see the required project structure gets created.

Related Posts:

Updating Build Script

Modify build.gradle file to include all required dependencies so that it looks like below. It downloads all the required jars from maven repository.

buildscript {
	ext {
		springBootVersion = '2.1.4.RELEASE'
	}
    repositories {
    	mavenLocal()
    	mavenCentral()
    }
    dependencies {
    	classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
    }
}
apply plugin: 'java'
apply plugin: 'org.springframework.boot'
sourceCompatibility = 1.8
targetCompatibility = 1.8
repositories {
	mavenLocal()
    mavenCentral()
}
dependencies {
	compile("org.springframework.boot:spring-boot-starter-batch:${springBootVersion}")
	compile("org.springframework:spring-oxm:5.1.7.RELEASE")
	runtime("com.h2database:h2:1.4.197")
}

In the above build script we have added spring-oxm to get benefits of JAXB classes for generating XML file from Java POJO class.

Creating VO Class

Create a model class Person.java which will represent a row of data for inputs and outputs. I have made the below class JAXB annotation enabled for converting Java object to XML file directly.

package com.roytuts.spring.batch.vo;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
@XmlRootElement(name = "person")
public class Person {
	private int id;
	private String firstName;
	private String lastName;
	@XmlAttribute(name = "id")
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	@XmlElement(name = "firstName")
	public String getFirstName() {
		return firstName;
	}
	public void setFirstName(String firstName) {
		this.firstName = firstName;
	}
	@XmlElement(name = "lastName")
	public String getLastName() {
		return lastName;
	}
	public void setLastName(String lastName) {
		this.lastName = lastName;
	}
	@Override
	public String toString() {
		return "Person [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + "]";
	}
}

Creating FieldSetMapper Class

Create below mapper class which will map the CSV file row item to Java object.

package com.roytuts.spring.batch.fieldset.mapper;
import org.springframework.batch.item.file.mapping.FieldSetMapper;
import org.springframework.batch.item.file.transform.FieldSet;
import com.roytuts.spring.batch.vo.Person;
public class PersonFieldSetMapper implements FieldSetMapper<Person> {
	@Override
	public Person mapFieldSet(FieldSet fieldSet) {
		Person person = new Person();
		person.setId(fieldSet.readInt(0));
		person.setFirstName(fieldSet.readString(1));
		person.setLastName(fieldSet.readString(2));
		return person;
	}
}

Creating ItemProcessor Class

Create an intermediate processor. A common paradigm in batch processing is to ingest data, transform it, and then pipe it out somewhere else. Here we write a simple transformer that converts the initial characters of the names to uppercase.

package com.roytuts.spring.batch.itemprocessor;
import org.springframework.batch.item.ItemProcessor;
import com.roytuts.spring.batch.vo.Person;
public class PersonItemProcessor implements ItemProcessor<Person, Person> {
	@Override
	public Person process(Person person) throws Exception {
		System.out.println("Processing: " + person);
		final String initCapFirstName = person.getFirstName().substring(0, 1).toUpperCase()
				+ person.getFirstName().substring(1);
		final String initCapLastName = person.getLastName().substring(0, 1).toUpperCase()
				+ person.getLastName().substring(1);
		Person transformedPerson = new Person();
		transformedPerson.setId(person.getId());
		transformedPerson.setFirstName(initCapFirstName);
		transformedPerson.setLastName(initCapLastName);
		return transformedPerson;
	}
}

Creating CSV File

Create below CSV file under src/main/resources directory.

1000,soumitra,roy
1001,souvik,sanyal
1002,arup,chatterjee
1003,suman,mukherjee
1004,debina,guha
1005,liton,sarkar
1006,debabrata,poddar

Creating Configuration Class

We have created this Spring Configuration class to define several beans for Spring Batch processing.

We have defined beans, such as, ItemProcessor, TransactionManager, JobRepository, DataSource, JobLauncher, Step, Job etc. for our Spring Batch processing.

We used Jaxb2Marshaller to marshall Java POJO to XML. We write the final output into an XML file (person.xml) under C:/workspace directory.

Note we have used (destroyMethod = “”) on StaxEventItemWriter to resolve the below error:

Attention
Destroy method 'close' on bean with name 'staxEventItemWriter' threw an exception: java.lang.NullPointerException
package com.roytuts.spring.batch.config;
import javax.sql.DataSource;
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.launch.JobLauncher;
import org.springframework.batch.core.launch.support.RunIdIncrementer;
import org.springframework.batch.core.launch.support.SimpleJobLauncher;
import org.springframework.batch.core.repository.JobRepository;
import org.springframework.batch.core.repository.support.JobRepositoryFactoryBean;
import org.springframework.batch.item.ItemProcessor;
import org.springframework.batch.item.ItemReader;
import org.springframework.batch.item.ItemWriter;
import org.springframework.batch.item.file.FlatFileItemReader;
import org.springframework.batch.item.file.mapping.DefaultLineMapper;
import org.springframework.batch.item.file.transform.DelimitedLineTokenizer;
import org.springframework.batch.item.xml.StaxEventItemWriter;
import org.springframework.batch.support.DatabaseType;
import org.springframework.batch.support.transaction.ResourcelessTransactionManager;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Scope;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.FileSystemResource;
import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseBuilder;
import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseType;
import org.springframework.oxm.jaxb.Jaxb2Marshaller;
import com.roytuts.spring.batch.fieldset.mapper.PersonFieldSetMapper;
import com.roytuts.spring.batch.itemprocessor.PersonItemProcessor;
import com.roytuts.spring.batch.vo.Person;
@Configuration
@EnableBatchProcessing
public class SpringBatchConfig {
	@Bean
	@Scope(value = BeanDefinition.SCOPE_PROTOTYPE)
	public Person person() {
		return new Person();
	}
	@Bean
	@Scope(value = BeanDefinition.SCOPE_PROTOTYPE)
	public ItemProcessor<Person, Person> itemProcessor() {
		return new PersonItemProcessor();
	}
	@Bean
	public DataSource dataSource() {
		EmbeddedDatabaseBuilder embeddedDatabaseBuilder = new EmbeddedDatabaseBuilder();
		return embeddedDatabaseBuilder.addScript("classpath:org/springframework/batch/core/schema-drop-h2.sql")
				.addScript("classpath:org/springframework/batch/core/schema-h2.sql").setType(EmbeddedDatabaseType.H2)
				.build();
	}
	@Bean
	public ResourcelessTransactionManager txManager() {
		return new ResourcelessTransactionManager();
	}
	@Bean
	public JobRepository jbRepository(DataSource dataSource, ResourcelessTransactionManager transactionManager)
			throws Exception {
		JobRepositoryFactoryBean factory = new JobRepositoryFactoryBean();
		factory.setDatabaseType(DatabaseType.H2.getProductName());
		factory.setDataSource(dataSource);
		factory.setTransactionManager(transactionManager);
		return factory.getObject();
	}
	@Bean
	public JobLauncher jbLauncher(JobRepository jobRepository) {
		SimpleJobLauncher jobLauncher = new SimpleJobLauncher();
		jobLauncher.setJobRepository(jobRepository);
		return jobLauncher;
	}
	@Bean
	public Jaxb2Marshaller jaxb2Marshaller() {
		Jaxb2Marshaller jaxb2Marshaller = new Jaxb2Marshaller();
		jaxb2Marshaller.setClassesToBeBound(Person.class);
		return jaxb2Marshaller;
	}
	@Bean
	public FlatFileItemReader<Person> fileItemReader() {
		FlatFileItemReader<Person> fileItemReader = new FlatFileItemReader<>();
		fileItemReader.setResource(new ClassPathResource("person.csv"));
		DelimitedLineTokenizer delimitedLineTokenizer = new DelimitedLineTokenizer();
		delimitedLineTokenizer.setNames("id", "firstName", "lastName");
		DefaultLineMapper<Person> defaultLineMapper = new DefaultLineMapper<>();
		defaultLineMapper.setLineTokenizer(delimitedLineTokenizer);
		defaultLineMapper.setFieldSetMapper(new PersonFieldSetMapper());
		fileItemReader.setLineMapper(defaultLineMapper);
		return fileItemReader;
	}
	@Bean(destroyMethod = "")
	public StaxEventItemWriter<Person> staxEventItemWriter(Jaxb2Marshaller marshaller) {
		StaxEventItemWriter<Person> staxEventItemWriter = new StaxEventItemWriter<>();
		staxEventItemWriter.setResource(new FileSystemResource("C:/workspace/person.xml"));
		staxEventItemWriter.setMarshaller(marshaller);
		staxEventItemWriter.setRootTagName("personInfo");
		return staxEventItemWriter;
	}
	@Bean
	public Job jobCsvXml(JobBuilderFactory jobBuilderFactory, Step step) {
		return jobBuilderFactory.get("jobCsvXml").incrementer(new RunIdIncrementer()).flow(step).end().build();
	}
	@Bean
	public Step step1(StepBuilderFactory stepBuilderFactory, ResourcelessTransactionManager transactionManager,
			ItemReader<Person> reader, ItemWriter<Person> writer, ItemProcessor<Person, Person> processor) {
		return stepBuilderFactory.get("step1").transactionManager(transactionManager).<Person, Person>chunk(2)
				.reader(reader).processor(processor).writer(writer).build();
	}
}

We have used here in-memory H2 database for our Spring Batch processing. It initializes the database for automatically creating spring batch job meta tables in H2 database.

You can also use other database, such as, MySQL, Oracle etc.

Note here we are including SQL scripts while configuring datasource for H2 database but these SQL scripts are loaded from Spring API. So you don’t need to create any SQL scripts here.

Attention

A default simple implementation of the Job interface is provided by Spring Batch in the form of the SimpleJob class which creates some standard functionality on top of Job, however the batch namespace abstracts away the need to instantiate it directly.

A Step is a domain object that encapsulates an independent, sequential phase of a batch job. Therefore, every Job is composed entirely of one or more steps. A Step contains all of the information necessary to define and control the actual batch processing.

ItemReader is an abstraction that represents the retrieval of input for a Step, one item at a time.

ItemWriter is an abstraction that represents the output of a Step, one batch or chunk of items at a time. Generally, an item writer has no knowledge of the input it will receive next, only the item that was passed in its current invocation.

ItemProcessor is an abstraction that represents the business processing of an item. While the ItemReader reads one item, and the ItemWriter writes them, the ItemProcessor provides access to transform or apply other business processing. If, while processing the item, it is determined that the item is not valid, returning null indicates that the item should not be written out.

TransactionManager – Spring’s that will be used to begin and commit transactions during processing.

Chunk – The number of items that will be processed before the transaction is committed.

JobRepository is the persistence mechanism. It provides CRUD operations for JobLauncher, Job and Step implementations. When a Job is first launched, a JobExecution is obtained from the repository, and during the course of execution StepExecution and JobExecution implementations are persisted by passing them to the repository.

JonLauncher represents a simple interface for launching a Job with a given set of JobParameters.

Creating Main Class

Create below class for launching spring batch job.

package com.roytuts.spring.batch;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication(scanBasePackages = "com.roytuts.spring.batch")
public class SpringBatch {
	public static void main(String[] args) {
		SpringApplication.run(SpringBatch.class, args);
	}
}

Testing the Application

Run the above class, you will see the below output.

Processing: Person [id=1000, firstName=soumitra, lastName=roy]
Processing: Person [id=1001, firstName=souvik, lastName=sanyal]
Processing: Person [id=1002, firstName=arup, lastName=chatterjee]
Processing: Person [id=1003, firstName=suman, lastName=mukherjee]
Processing: Person [id=1004, firstName=debina, lastName=guha]
Processing: Person [id=1005, firstName=liton, lastName=sarkar]
Processing: Person [id=1006, firstName=debabrata, lastName=poddar]

In the above output you see the job name, step name and also which row item from csv file is being processed.

If you use other than in-memory database, such as, MySQL, Oracle etc. then you can also see the SQL scripts have been executed and below tables have been created in the MySQL database with job details.

spring batch tables

Source Code

Thanks for reading.

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