Spring Batch MultiResourceItemReader example(八)

In this tutorial, we will show you how to read items from multiple resources (multiple csv files), and write the items into a single csv file.

Tools and libraries used

1. Maven 3
2. Eclipse 4.2
3. JDK 1.6
4. Spring Core 3.2.2.RELEASE
5. Spring Batch 2.2.0.RELEASE

P.S This example – 3 CSV files (reader) – combine into a single CSV file (writer).

1. Project Directory Structure

Review the final project structure, a standard Maven project.

2. Multiple CSV Files

There are 3 csv files, later we will use MultiResourceItemReader to read it one by one.

csv/inputs/domain-1-3-2013.csv

1,facebook.com
2,yahoo.com
3,google.com

csv/inputs/domain-2-3-2013.csv

200,mkyong.com
300,stackoverflow.com
400,oracle.com

csv/inputs/domain-3-3-2013.csv

999,eclipse.org
888,baidu.com

3. Spring Batch Jobs

A job to read resources that matches this pattern csv/inputs/domain-*.csv, and write it into a single cvs filedomain.all.csv.

resources/spring/batch/jobs/job-read-files.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
        xmlns:batch="http://www.springframework.org/schema/batch" 
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://www.springframework.org/schema/batch 
	http://www.springframework.org/schema/batch/spring-batch-2.2.xsd
	http://www.springframework.org/schema/beans 
	http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
	">

  <import resource="../config/context.xml" />

  <bean id="domain" class="com.mkyong.Domain" />

  <job id="readMultiFileJob" xmlns="http://www.springframework.org/schema/batch">
    <step id="step1">
	<tasklet>
		<chunk reader="multiResourceReader" writer="flatFileItemWriter"
			commit-interval="1" />
	</tasklet>
    </step>
  </job>

  <bean id="multiResourceReader"
	class=" org.springframework.batch.item.file.MultiResourceItemReader">
	<property name="resources" value="file:csv/inputs/domain-*.csv" />
	<property name="delegate" ref="flatFileItemReader" />
  </bean>

  <bean id="flatFileItemReader" 
        class="org.springframework.batch.item.file.FlatFileItemReader">
	<property name="lineMapper">
	  <bean class="org.springframework.batch.item.file.mapping.DefaultLineMapper">
		<property name="lineTokenizer">
		    <bean 
                    class="org.springframework.batch.item.file.transform.DelimitedLineTokenizer">
				<property name="names" value="id, domain" />
		    </bean>
		</property>
		<property name="fieldSetMapper">
		    <bean
		    class="org.springframework.batch.item.file.mapping.BeanWrapperFieldSetMapper">
				<property name="prototypeBeanName" value="domain" />
		    </bean>
		</property>
	  </bean>
	</property>
  </bean>

  <bean id="flatFileItemWriter" 
          class="org.springframework.batch.item.file.FlatFileItemWriter">
	<property name="resource" value="file:csv/outputs/domain.all.csv" />
	<property name="appendAllowed" value="true" />
	<property name="lineAggregator">
	  <bean
	  class="org.springframework.batch.item.file.transform.DelimitedLineAggregator">
		<property name="delimiter" value="," />
		<property name="fieldExtractor">
		  <bean	
                  class="org.springframework.batch.item.file.transform.BeanWrapperFieldExtractor">
			<property name="names" value="id, domain" />
		  </bean>
		</property>
	  </bean>
	</property>
  </bean>

</beans>

resources/spring/batch/config/context.xml

<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="
	http://www.springframework.org/schema/beans 
	http://www.springframework.org/schema/beans/spring-beans-3.2.xsd">

    <!-- stored job-meta in memory --> 
    <bean id="jobRepository"
	class="org.springframework.batch.core.repository.support.MapJobRepositoryFactoryBean">
	<property name="transactionManager" ref="transactionManager" />
    </bean>
 	
    <bean id="transactionManager"
	class="org.springframework.batch.support.transaction.ResourcelessTransactionManager" />
	 
    <bean id="jobLauncher"
	class="org.springframework.batch.core.launch.support.SimpleJobLauncher">
	<property name="jobRepository" ref="jobRepository" />
    </bean>

</beans>

4. Run It

Create a Java class and run the batch job.

App.java

package com.mkyong;

import org.springframework.batch.core.Job;
import org.springframework.batch.core.JobExecution;
import org.springframework.batch.core.JobParameters;
import org.springframework.batch.core.launch.JobLauncher;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class App {

  public static void main(String[] args) {
	App obj = new App();
	obj.run();
  }

  private void run() {

	String[] springConfig = { "spring/batch/jobs/job-read-files.xml" };

	ApplicationContext context = new ClassPathXmlApplicationContext(springConfig);

	JobLauncher jobLauncher = (JobLauncher) context.getBean("jobLauncher");
	Job job = (Job) context.getBean("readMultiFileJob");

	try {

		JobExecution execution = jobLauncher.run(job, new JobParameters());
		System.out.println("Exit Status : " + execution.getStatus());

	} catch (Exception e) {
		e.printStackTrace();
	}

	System.out.println("Done");

  }

}

Output. The content of three csv files is read and combine into a single csv file.

csv/outputs/domain.all.csv

1,facebook.com
2,yahoo.com
3,google.coms
200,mkyong.com
300,stackoverflow.com
400,oracle.com
999,eclipse.org
888,baidu.com