In this post, we will show you how to configure a Spring Batch job to read data from mysql database and write into XML file.

Project structure

This is a directory structure of the standard gradle project.

Project dependencies

task wrapper(type: Wrapper) {
 gradleVersion = '3.2.1'
}
apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'org.springframework.boot'
sourceCompatibility = 1.8
repositories {
 mavenLocal()
 mavenCentral()
}
dependencies {
 compile 'org.springframework.boot:spring-boot-starter-data-jpa:1.5.2.RELEASE'
 compile 'org.springframework:spring-oxm:4.3.7.RELEASE'
 compileOnly('org.projectlombok:lombok:1.16.12')
 runtime('mysql:mysql-connector-java')
 compile('org.springframework.boot:spring-boot-starter-batch:1.5.2.RELEASE')
 testCompile('org.springframework.boot:spring-boot-starter-test:1.5.2.RELEASE')
}
buildscript {
 repositories {
 mavenLocal()
 jcenter()
 }
 dependencies {
 classpath "org.springframework.boot:spring-boot-gradle-plugin:1.5.2.RELEASE"
 }
}

application.properties file

spring.datasource.url=jdbc:mysql://localhost:3306/spring_batch
spring.datasource.username=root
spring.datasource.password=santosh
spring.jpa.hibernate.ddl-auto=update

(追記) (追記ここまで)

Spring Batch Jobs

Create a job which will read from mysql database using named query on user table and write into XML file.

package com.walking.techie.mysqltoxml.jobs;
import com.walking.techie.mysqltoxml.model.User;
import com.walking.techie.mysqltoxml.orm.JpaQueryProviderImpl;
import java.util.HashMap;
import java.util.Map;
import javax.persistence.EntityManagerFactory;
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.item.database.JpaPagingItemReader;
import org.springframework.batch.item.xml.StaxEventItemWriter;
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 org.springframework.oxm.xstream.XStreamMarshaller;
@Configuration
@EnableBatchProcessing
public class ReadFromDB {
 @Autowired
 private JobBuilderFactory jobBuilderFactory;
 @Autowired
 private StepBuilderFactory stepBuilderFactory;
 @Autowired
 private EntityManagerFactory entityManagerFactory;
 @Bean
 public Job readUser() throws Exception {
 return jobBuilderFactory.get("readUser").flow(step1()).end().build();
 }
 @Bean
 public Step step1() throws Exception {
 return stepBuilderFactory.get("step1").<User, User>chunk(10).reader(reader()).writer(writer())
 .build();
 }
 @Bean
 public JpaPagingItemReader<User> reader() throws Exception {
 JpaPagingItemReader<User> databaseReader = new JpaPagingItemReader<>();
 databaseReader.setEntityManagerFactory(entityManagerFactory);
 JpaQueryProviderImpl<User> jpaQueryProvider = new JpaQueryProviderImpl<>();
 jpaQueryProvider.setQuery("User.findAll");
 databaseReader.setQueryProvider(jpaQueryProvider);
 databaseReader.setPageSize(1000);
 databaseReader.afterPropertiesSet();
 return databaseReader;
 }
 @Bean
 public StaxEventItemWriter<User> writer() {
 StaxEventItemWriter<User> writer = new StaxEventItemWriter<>();
 writer.setResource(new FileSystemResource("xml/user.xml"));
 writer.setMarshaller(userUnmarshaller());
 writer.setRootTagName("users");
 return writer;
 }
 @Bean
 public XStreamMarshaller userUnmarshaller() {
 XStreamMarshaller unMarshaller = new XStreamMarshaller();
 Map<String, Class> aliases = new HashMap<String, Class>();
 aliases.put("user", User.class);
 unMarshaller.setAliases(aliases);
 return unMarshaller;
 }
}

Map record from mysql user table User object and write to XML file.

A Java model class

package com.walking.techie.mysqltoxml.model;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;
import lombok.Data;
@NamedQueries({
 @NamedQuery(name = "User.findAll", query = "select u from User u")
})
@Table(name = "user")
@Data
@Entity
public class User {
 @Id
 int id;
 String username;
 String password;
 int age;
}

JpaQueryProviderImpl provide mothods to create named query using Jpa

package com.walking.techie.mysqltoxml.orm;
import javax.persistence.Query;
import org.springframework.batch.item.database.orm.AbstractJpaQueryProvider;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;
public class JpaQueryProviderImpl<E> extends AbstractJpaQueryProvider {
 private Class<E> entityClass;
 private String query;
 @Override
 public Query createQuery() {
 return getEntityManager().createNamedQuery(query, entityClass);
 }
 public void setQuery(String query) {
 this.query = query;
 }
 public void setEntityClass(Class<E> entityClazz) {
 this.entityClass = entityClazz;
 }
 @Override
 public void afterPropertiesSet() throws Exception {
 Assert.isTrue(StringUtils.hasText(query), "Query cannot be empty");
 Assert.notNull(entityClass, "Entity class cannot be NULL");
 }
}

Run Application

package com.walking.techie;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class Application {
 public static void main(String[] args) {
 SpringApplication.run(Application.class, args);
 }
}

Output

Output of the application will store in xml/user.xml

<?xml version="1.0" encoding="UTF-8"?><users><user><id>1</id><username>santosh</username><password>password</password><age>30</age></user><user><id>2</id><username>santosh</username><password>password</password><age>24</age></user><user><id>3</id><username>santosh</username><password>password</password><age>22</age></user><user><id>4</id><username>santosh</username><password>password</password><age>28</age></user><user><id>5</id><username>santosh</username><password>password</password><age>34</age></user><user><id>6</id><username>santosh</username><password>password</password><age>20</age></user></users>

output on console

2017年03月26日 20:42:44.548 INFO 8027 --- [ main] o.s.b.c.l.support.SimpleJobLauncher : Job: [FlowJob: [name=readUser]] launched with the following parameters: [{}]
2017年03月26日 20:42:44.608 INFO 8027 --- [ main] o.s.batch.core.job.SimpleStepHandler : Executing step: [step1]
2017年03月26日 20:42:44.725 INFO 8027 --- [ main] o.s.b.c.l.support.SimpleJobLauncher : Job: [FlowJob: [name=readUser]] completed with the following parameters: [{}] and the following status: [COMPLETED]

Note : This code has been compiled and run on mac notebook and intellij IDEA.