@AllArgsConstructor
@NoArgsConstructor
@Data
@Builder
public class Employee {
    private String empId;
    private String firstName;
    private String lastName;
    private String role;
	@Override
	public String toString() {
		return empId + ","+ firstName+ ","+ lastName+ ","+ role;
	}
}

package com.example;

import org.springframework.batch.item.ItemWriter;
import org.springframework.classify.Classifier;

import lombok.Setter;


@Setter
public class EmployeeClassifier implements Classifier<Employee, ItemWriter<? super Employee>> {
    private static final long serialVersionUID = 1L;
    private ItemWriter<Employee> javaDeveloperFileItemWriter;
    private ItemWriter<Employee> pythonDeveloperFileItemWriter;
    private ItemWriter<Employee> cloudDeveloperFileItemWriter;
    
    public EmployeeClassifier() {
    	
    }

    public EmployeeClassifier(ItemWriter<Employee> javaDeveloperFileItemWriter,
                              ItemWriter<Employee> pythonDeveloperFileItemWriter,
                              ItemWriter<Employee> cloudDeveloperFileItemWriter) {
        this.javaDeveloperFileItemWriter = javaDeveloperFileItemWriter;
        this.pythonDeveloperFileItemWriter = pythonDeveloperFileItemWriter;
        this.cloudDeveloperFileItemWriter = cloudDeveloperFileItemWriter;
    }

    @Override
    public ItemWriter<? super Employee> classify(Employee employee) {
        if(employee.getRole().equals("Java Developer")){
            return javaDeveloperFileItemWriter;
        }
        else if(employee.getRole().equals("Python Developer")){
            return pythonDeveloperFileItemWriter;
        }
        return cloudDeveloperFileItemWriter;
    }
}

package com.example;

import org.springframework.batch.item.file.mapping.FieldSetMapper;
import org.springframework.batch.item.file.transform.FieldSet;
import org.springframework.validation.BindException;

public class EmployeeFieldSetMapper implements FieldSetMapper<Employee> {
    @Override
    public Employee mapFieldSet(FieldSet fieldSet) throws BindException {
        return Employee.builder()
                .empId(fieldSet.readRawString("empId"))
                .firstName(fieldSet.readRawString("firstName"))
                .lastName(fieldSet.readRawString("lastName"))
                .role(fieldSet.readRawString("role"))
                .build();
    }
}

package com.example;

import org.springframework.batch.core.Job;
import org.springframework.batch.core.Step;
import org.springframework.batch.core.configuration.annotation.JobBuilderFactory;
import org.springframework.batch.core.configuration.annotation.StepBuilderFactory;
import org.springframework.batch.item.ItemWriter;
import org.springframework.batch.item.file.FlatFileItemReader;
import org.springframework.batch.item.file.FlatFileItemWriter;
import org.springframework.batch.item.file.builder.FlatFileItemReaderBuilder;
import org.springframework.batch.item.file.builder.FlatFileItemWriterBuilder;
import org.springframework.batch.item.file.builder.MultiResourceItemWriterBuilder;
import org.springframework.batch.item.file.mapping.DefaultLineMapper;
import org.springframework.batch.item.file.transform.DelimitedLineTokenizer;
import org.springframework.batch.item.file.transform.PassThroughLineAggregator;
import org.springframework.batch.item.support.ClassifierCompositeItemWriter;
import org.springframework.batch.item.support.builder.ClassifierCompositeItemWriterBuilder;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.classify.Classifier;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.FileSystemResource;

@Configuration
public class MyJobConfig {

	@Autowired
	private JobBuilderFactory jobBuilderFactory;
	@Autowired
	private StepBuilderFactory stepBuilderFactory;
	
	@Bean
    public FlatFileItemReader<Employee> itemReader() {
        DelimitedLineTokenizer tokenizer = new DelimitedLineTokenizer();
        tokenizer.setNames("empId", "firstName", "lastName", "role");

        DefaultLineMapper<Employee> employeeLineMapper = new DefaultLineMapper<>();
        employeeLineMapper.setLineTokenizer(tokenizer);
        employeeLineMapper.setFieldSetMapper(new EmployeeFieldSetMapper());
        employeeLineMapper.afterPropertiesSet();

        return new FlatFileItemReaderBuilder<Employee>()
                .name("flatFileReader")
                .linesToSkip(1)
                .resource(new ClassPathResource("employee.csv"))
                .lineMapper(employeeLineMapper)
                .build();
    }

    @Bean
    public ClassifierCompositeItemWriter<Employee> classifierCompositeItemWriter() throws Exception {
        Classifier<Employee, ItemWriter<? super Employee>> classifier =
                new EmployeeClassifier(javaDeveloperItemWriter(), pythonDeveloperItemWriter(), cloudDeveloperItemWriter());
        return new ClassifierCompositeItemWriterBuilder<Employee>()
                .classifier(classifier)
                .build();
    }

    @Bean
    public ItemWriter<Employee> javaDeveloperItemWriter() {
        FlatFileItemWriter<Employee> itemWriter = new FlatFileItemWriterBuilder<Employee>()
                .lineAggregator(new PassThroughLineAggregator<>())
                .name("itemsWriter")
                .build();

        return new MultiResourceItemWriterBuilder<Employee>()
                .name("javaDeveloperItemWriter")
                .delegate(itemWriter)
                .resource(new FileSystemResource("javaDeveloper-employee.csv"))
                .itemCountLimitPerResource(2)
                .resourceSuffixCreator(index -> "-" + index)
                .build();
    }

    @Bean
    public ItemWriter<Employee> pythonDeveloperItemWriter() {
        FlatFileItemWriter<Employee> itemWriter = new FlatFileItemWriterBuilder<Employee>()
                .lineAggregator(new PassThroughLineAggregator<>())
                .name("itemsWriter")
                .build();

        return new MultiResourceItemWriterBuilder<Employee>()
                .name("pythonDeveloperItemWriter")
                .delegate(itemWriter)
                .resource(new FileSystemResource("pythonDeveloper-employee.csv"))
                .itemCountLimitPerResource(2)
                .resourceSuffixCreator(index -> "-" + index)
                .build();
    }

    @Bean
    public ItemWriter<Employee> cloudDeveloperItemWriter() {
        FlatFileItemWriter<Employee> itemWriter = new FlatFileItemWriterBuilder<Employee>()
                .lineAggregator(new PassThroughLineAggregator<>())
                .name("itemsWriter")
                .build();

        return new MultiResourceItemWriterBuilder<Employee>()
                .name("cloudDeveloperItemWriter")
                .delegate(itemWriter)
                .resource(new FileSystemResource("cloudDeveloper-employee.csv"))
                .itemCountLimitPerResource(2)
                .resourceSuffixCreator(index -> "-" + index)
                .build();
    }

    @Bean
    public Step step() throws Exception {
        return stepBuilderFactory.get("step")
                .<Employee, Employee>chunk(1)
                .reader(itemReader())
                .writer(classifierCompositeItemWriter())
                .build();
    }

    @Bean
    public Job job() throws Exception {
        return jobBuilderFactory.get("job")
                .start(step())
                .build();
    }
}

package com.example;

import org.springframework.batch.core.configuration.annotation.EnableBatchProcessing;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;

@EnableBatchProcessing
@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})
public class SpringBatchMultipleFilesWithCompositeApplication {

	public static void main(String[] args) {
		SpringApplication.run(SpringBatchMultipleFilesWithCompositeApplication.class, args);
	}
}