HowToDoInJava

Spring Batch FlatFileItemReader – Read CSV Example

By Lokesh Gupta | 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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About Lokesh Gupta

A family guy with fun loving nature. Love computers, programming and solving everyday problems. Find me on Facebook and Twitter.

Feedback, Discussion and Comments

  1. David Fanjkutic

    this does not work for CSV records that are multi-line

    Reply

  2. Amith

    How can the above code be enhanced to validate the inputs. Lets assume firstname and lastname can be of size max 5 length. How can the code be modified to include the constraints along with exception handling

    Reply

  3. Sweety

    Hi I am new to Java can you please tell me what chnages required for Postgres DB

    Reply

  4. chaimae

    when im trying to run the project i got this error :
    PLICATION FAILED TO START
    ***************************

    Description:

    Field jobLauncher in com.example.demo.App required a bean of type ‘org.springframework.batch.core.launch.JobLauncher’ that could not be found.

    The injection point has the following annotations:
    – @org.springframework.beans.factory.annotation.Autowired(required=true)

    Action:

    Consider defining a bean of type ‘org.springframework.batch.core.launch.JobLauncher’ in your configuration.

    Reply

    • Dhruv

      Hi chaimae,
      You got resolved this issue? I am having same issue.

      Thanks

      Reply

  5. govind

    i am not able ad new files in the directory . reader doesn’t read the record from the directory which newly added .

    Reply

  6. Priyanka Sinha

    Hi,

    I am working on spring application. I am reading csv or excel file with very large dataset. Please provide me some reference for this using spring batch and printing to console for Spring application, not SpringBoot app. Above given example is for SpringBoot application.

    I have written BatchConfig and console writer classes. I am not able to test it as App class mentioned above is for springboot application, not for spring. Could you please help me in writing App class for spring application and testing it?

    Thanks in advance.

    Reply

  7. Priyanka Sinha

    Please provide me some reference for reading csv or excel file using spring batch and printing to console for Spring application, not SpringBoot app. Above given example is for SpringBoot application.

    Thanks in advance.

    Reply

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