Learn to read multiple CSV files from filesystem or resources folder using MultiResourceItemReader class. These files may have first rows as header, so do not forget to skip first line.
Table of Contents Project Structure Read CSV files with MultiResourceItemReader Write rows to console Maven Dependency Demo
Project Structure
In this project, we will –
- Read 3 CSV files from
input/*.csv. - Write data to console.
Read CSV files with MultiResourceItemReader
You need to use MultiResourceItemReader to read lines from CSV file. It reads items from multiple resources sequentially.
@Value("input/inputData*.csv")
private Resource[] inputResources;
@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(multiResourceItemReader())
.writer(writer())
.build();
}
@Bean
public MultiResourceItemReader<Employee> multiResourceItemReader()
{
MultiResourceItemReader<Employee> resourceItemReader = new MultiResourceItemReader<Employee>();
resourceItemReader.setResources(inputResources);
resourceItemReader.setDelegate(reader());
return resourceItemReader;
}
@Bean
public FlatFileItemReader<Employee> reader()
{
//Create reader instance
FlatFileItemReader<Employee> reader = new FlatFileItemReader<Employee>();
//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;
}
public class Employee {
String id;
String firstName;
String lastName;
//public setter and getter methods
}
id,firstName,lastName 1,Lokesh,Gupta 2,Amit,Mishra 3,Pankaj,Kumar 4,David,Miller
id,firstName,lastName 5,Ramesh,Gupta 6,Vineet,Mishra 7,Amit,Kumar 8,Dav,Miller
id,firstName,lastName 9,Vikas,Kumar 10,Pratek,Mishra 11,Brian,Kumar 12,David,Cena
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 https://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.MultiResourceItemReader;
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.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.Resource;
import com.howtodoinjava.demo.model.Employee;
@Configuration
@EnableBatchProcessing
public class BatchConfig
{
@Autowired
private JobBuilderFactory jobBuilderFactory;
@Autowired
private StepBuilderFactory stepBuilderFactory;
@Value("input/inputData*.csv")
private Resource[] inputResources;
@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(multiResourceItemReader())
.writer(writer())
.build();
}
@Bean
public MultiResourceItemReader<Employee> multiResourceItemReader()
{
MultiResourceItemReader<Employee> resourceItemReader = new MultiResourceItemReader<Employee>();
resourceItemReader.setResources(inputResources);
resourceItemReader.setDelegate(reader());
return resourceItemReader;
}
@SuppressWarnings({ "rawtypes", "unchecked" })
@Bean
public FlatFileItemReader<Employee> reader()
{
//Create reader instance
FlatFileItemReader<Employee> reader = new FlatFileItemReader<Employee>();
//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>();
}
}
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 15:32:26 INFO - Starting App on XYZ with PID 4596 (C:\Users\user\workspace\App\target\classes started by zkpkhua in C:\Users\user\workspace\App)
2018-07-10 15:32:26 INFO - No active profile set, falling back to default profiles: default
2018-07-10 15:32:27 INFO - Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@3c9d0b9d: startup date [Tue Jul 10 15:32:27 IST 2018]; root of context hierarchy
2018-07-10 15:32:28 INFO - HikariPool-1 - Starting...
2018-07-10 15:32:29 INFO - HikariPool-1 - Start completed.
2018-07-10 15:32:29 INFO - No database type set, using meta data indicating: H2
2018-07-10 15:32:29 INFO - No TaskExecutor has been set, defaulting to synchronous executor.
2018-07-10 15:32:29 INFO - Executing SQL script from class path resource [org/springframework/batch/core/schema-h2.sql]
2018-07-10 15:32:29 INFO - Executed SQL script from class path resource [org/springframework/batch/core/schema-h2.sql] in 68 ms.
2018-07-10 15:32:30 INFO - Registering beans for JMX exposure on startup
2018-07-10 15:32:30 INFO - Bean with name 'dataSource' has been autodetected for JMX exposure
2018-07-10 15:32:30 INFO - Located MBean 'dataSource': registering with JMX server as MBean [com.zaxxer.hikari:name=dataSource,type=HikariDataSource]
2018-07-10 15:32:30 INFO - No TaskScheduler/ScheduledExecutorService bean found for scheduled processing
2018-07-10 15:32:30 INFO - Started App in 4.036 seconds (JVM running for 4.827)
2018-07-10 15:33:00 INFO - Job: [SimpleJob: [name=readCSVFilesJob]] launched with the following parameters: [{JobID=1531216980005}]
2018-07-10 15:33:00 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]
Employee [id=5, firstName=Ramesh, lastName=Gupta]
Employee [id=6, firstName=Vineet, lastName=Mishra]
Employee [id=7, firstName=Amit, lastName=Kumar]
Employee [id=8, firstName=Dav, lastName=Miller]
Employee [id=9, firstName=Vikas, lastName=Kumar]
Employee [id=10, firstName=Pratek, lastName=Mishra]
Employee [id=11, firstName=Brian, lastName=Kumar]
Employee [id=12, firstName=David, lastName=Cena]
2018-07-10 15:33:00 INFO - Job: [SimpleJob: [name=readCSVFilesJob]] completed with the following parameters: [{JobID=1531216980005}] and the following status: [COMPLETED]
Drop me your questions in comments section.
Happy Learning !!
Leave a Reply