HowToDoInJava

Spring Batch FlatFileItemReader – Read CSV Example

By | Filed Under: Spring Batch

Learn to read CSV file from filesystem or resources folder using FlatFileItemReader class.

Table of Contents

Project Structure
Read CSV with FlatFileItemReader
Write read rows to console
Maven Dependency
Demo

Project Structure

In this project, we will learn to –

  1. Read CSV file from input/inputData.csv.
  2. Write data to console.
Project Structure
Project Structure

Read CSV with FlatFileItemReader

You need to use FlatFileItemReader to read lines from CSV file.

@Bean
public FlatFileItemReader<Employee> reader() 
{
	//Create reader instance
	FlatFileItemReader<Employee> reader = new FlatFileItemReader<Employee>();
	
	//Set input file location
	reader.setResource(new FileSystemResource("input/inputData.csv"));
	
	//Set number of lines to skips. Use it if file has header rows.
	reader.setLinesToSkip(1); 	
	
	//Configure how each line will be parsed and mapped to different values
	reader.setLineMapper(new DefaultLineMapper() {
		{
			//3 columns in each row
			setLineTokenizer(new DelimitedLineTokenizer() {
				{
					setNames(new String[] { "id", "firstName", "lastName" });
				}
			});
			//Set values in Employee class
			setFieldSetMapper(new BeanWrapperFieldSetMapper<Employee>() {
				{
					setTargetType(Employee.class);
				}
			});
		}
	});
	return reader;
}

id,firstName,lastName
1,Lokesh,Gupta
2,Amit,Mishra
3,Pankaj,Kumar
4,David,Miller

Write read rows to console

Create ConsoleItemWriter class implementing ItemWriter interface.

import java.util.List;

import org.springframework.batch.item.ItemWriter;

public class ConsoleItemWriter<T> implements ItemWriter<T> { 
    @Override 
    public void write(List<? extends T> items) throws Exception { 
        for (T item : items) { 
            System.out.println(item); 
        } 
    } 
}

Use ConsoleItemWriter as writer.

@Bean
public ConsoleItemWriter<Employee> writer() 
{
	return new ConsoleItemWriter<Employee>();
}

Maven Dependency

Look at project dependencies.

<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.howtodoinjava</groupId>
	<artifactId>App</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>App</name>
	<url>http://maven.apache.org</url>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.0.3.RELEASE</version>
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-batch</artifactId>
		</dependency>
		<dependency>
			<groupId>com.h2database</groupId>
			<artifactId>h2</artifactId>
			<scope>runtime</scope>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

	<repositories>
		<repository>
			<id>repository.spring.release</id>
			<name>Spring GA Repository</name>
			<url>http://repo.spring.io/release</url>
		</repository>
	</repositories>
</project>

Demo

Before running the application, look at complete code of BatchConfig.java.

package com.howtodoinjava.demo.config;

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.support.RunIdIncrementer;
import org.springframework.batch.item.file.FlatFileItemReader;
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.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.FileSystemResource;

import com.howtodoinjava.demo.model.Employee;

@Configuration
@EnableBatchProcessing
public class BatchConfig 
{
	@Autowired
	private JobBuilderFactory jobBuilderFactory;
	
	@Autowired
	private StepBuilderFactory stepBuilderFactory;

	@Bean
	public Job readCSVFilesJob() {
		return jobBuilderFactory
				.get("readCSVFilesJob")
				.incrementer(new RunIdIncrementer())
				.start(step1())
				.build();
	}

	@Bean
	public Step step1() {
		return stepBuilderFactory.get("step1").<Employee, Employee>chunk(5)
				.reader(reader())
				.writer(writer())
				.build();
	}

	@SuppressWarnings({ "rawtypes", "unchecked" })
	@Bean
	public FlatFileItemReader<Employee> reader() 
	{
		//Create reader instance
		FlatFileItemReader<Employee> reader = new FlatFileItemReader<Employee>();
		
		//Set input file location
		reader.setResource(new FileSystemResource("input/inputData.csv"));
		
		//Set number of lines to skips. Use it if file has header rows.
		reader.setLinesToSkip(1); 	
		
		//Configure how each line will be parsed and mapped to different values
		reader.setLineMapper(new DefaultLineMapper() {
			{
				//3 columns in each row
				setLineTokenizer(new DelimitedLineTokenizer() {
					{
						setNames(new String[] { "id", "firstName", "lastName" });
					}
				});
				//Set values in Employee class
				setFieldSetMapper(new BeanWrapperFieldSetMapper<Employee>() {
					{
						setTargetType(Employee.class);
					}
				});
			}
		});
		return reader;
	}
	
	@Bean
	public ConsoleItemWriter<Employee> writer() 
	{
		return new ConsoleItemWriter<Employee>();
	}
}

public class Employee {

	String id;
	String firstName;
	String lastName;

	//public setter and getter methods
}

package com.howtodoinjava.demo;

import org.springframework.batch.core.Job;
import org.springframework.batch.core.JobParameters;
import org.springframework.batch.core.JobParametersBuilder;
import org.springframework.batch.core.launch.JobLauncher;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.Scheduled;

@SpringBootApplication
@EnableScheduling
public class App
{
    @Autowired
    JobLauncher jobLauncher;
     
    @Autowired
    Job job;
     
    public static void main(String[] args)
    {
        SpringApplication.run(App.class, args);
    }
     
    @Scheduled(cron = "0 */1 * * * ?")
    public void perform() throws Exception
    {
        JobParameters params = new JobParametersBuilder()
                .addString("JobID", String.valueOf(System.currentTimeMillis()))
                .toJobParameters();
        jobLauncher.run(job, params);
    }
}

#Disable batch job's auto start 
spring.batch.job.enabled=false

spring.main.banner-mode=off

Run the application

Run the application as Spring boot application, and watch the console. Batch job will start at start of each minute. It will read the input file, and print the read values in console.

2018-07-10 13:28:35 INFO  - Starting App on FFC15B4E9C5AA with PID 12060 (C:\Users\user\app\App\target\classes started by zkpkhua in C:\Users\user\app\App)
2018-07-10 13:28:35 INFO  - No active profile set, falling back to default profiles: default
2018-07-10 13:28:35 INFO  - Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@75329a49: startup date [Tue Jul 10 13:28:35 IST 2018]; root of context hierarchy
2018-07-10 13:28:37 INFO  - HikariPool-1 - Starting...
2018-07-10 13:28:38 INFO  - HikariPool-1 - Start completed.
2018-07-10 13:28:38 INFO  - No database type set, using meta data indicating: H2
2018-07-10 13:28:38 INFO  - No TaskExecutor has been set, defaulting to synchronous executor.
2018-07-10 13:28:39 INFO  - Executing SQL script from class path resource [org/springframework/batch/core/schema-h2.sql]
2018-07-10 13:28:39 INFO  - Executed SQL script from class path resource [org/springframework/batch/core/schema-h2.sql] in 74 ms.
2018-07-10 13:28:39 INFO  - Registering beans for JMX exposure on startup
2018-07-10 13:28:39 INFO  - Bean with name 'dataSource' has been autodetected for JMX exposure
2018-07-10 13:28:39 INFO  - Located MBean 'dataSource': registering with JMX server as MBean [com.zaxxer.hikari:name=dataSource,type=HikariDataSource]
2018-07-10 13:28:39 INFO  - No TaskScheduler/ScheduledExecutorService bean found for scheduled processing
2018-07-10 13:28:39 INFO  - Started App in 4.485 seconds (JVM running for 5.33)

2018-07-10 13:29:00 INFO  - Job: [SimpleJob: [name=readCSVFilesJob]] launched with the following parameters: [{JobID=1531209540004}]

2018-07-10 13:29:00 INFO  - Executing step: [step1]

Employee [id=1, firstName=Lokesh, lastName=Gupta]
Employee [id=2, firstName=Amit, lastName=Mishra]
Employee [id=3, firstName=Pankaj, lastName=Kumar]
Employee [id=4, firstName=David, lastName=Miller]

2018-07-10 13:29:00 INFO  - Job: [SimpleJob: [name=readCSVFilesJob]] completed with the following parameters: [{JobID=1531209540004}] and the following status: [COMPLETED]

Drop me your questions in comments section.

Happy Learning !!

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