Table of Contents
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.
Related Posts:
Prerequisites
Gradle 4.10.2, Spring Boot 2.1.4/2.6.7, Java 8+, Maven 3.8.5
Project Setup
Create gradle or maven based project in your favorite IDE or tool and you will see the required project structure gets created.
For maven based project you can use the following pom.xml file:
<?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.roytuts</groupId>
<artifactId>spring-batch-csv-to-xml</artifactId>
<version>0.0.1-SNAPSHOT</version>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>11</maven.compiler.source>
<maven.compiler.target>11</maven.compiler.target>
</properties>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.6.7</version>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-batch</artifactId>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-oxm</artifactId>
</dependency>
<dependency>
<groupId>jakarta.xml.bind</groupId>
<artifactId>jakarta.xml.bind-api</artifactId>
</dependency>
<dependency>
<groupId>org.glassfish.jaxb</groupId>
<artifactId>jaxb-runtime</artifactId>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>For gradle based project, 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 I have added spring-oxm to get benefits of JAXB classes for generating XML file from Java POJO class.
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.
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 + "]";
}
}FieldSetMapper Class
Create below mapper class which will map the CSV file row item to Java object.
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;
}
}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 I write a simple transformer that converts the initial characters of the names to uppercase.
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;
}
}Input CSV File
Create below CSV file under classpath directory – src/main/resources.
1000,soumitra,roy 1001,souvik,sanyal 1002,arup,chatterjee 1003,suman,mukherjee 1004,debina,guha 1005,liton,sarkar 1006,debabrata,poddar
Configuration Class
I have created this Spring Configuration class to define several beans for Spring Batch processing.
I have defined beans, such as, ItemProcessor, TransactionManager, JobRepository, DataSource, JobLauncher, Step, Job etc. for our Spring Batch processing.
I used Jaxb2Marshaller to marshall Java POJO to XML. I write the final output into an XML file (person.xml).
Note I have used (
destroyMethod = "") onStaxEventItemWriter()to resolve the below error:
Destroy method 'close' on bean with name 'staxEventItemWriter' threw an exception: java.lang.NullPointerExceptionimport 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.csvtoxml.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();
}
}I 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 I am 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.
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.
Spring Boot Main Class
Create below class for launching spring batch job.
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class SpringBatch {
public static void main(String[] args) {
SpringApplication.run(SpringBatch.class, args);
}
}Testing Spring Batch CSV to XML Conversion
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.
