Generating a CSV file

Write a CSV file as part of a read/process/write step.

Getting ready

We will generate a CSV file from User objects. Make sure that the User class exists:

public class User {
  private String firstName;
  private int age;

How to do it…

Use FlatFileItemWriter provided by Spring Batch:

1. Add a writer() method that will get the fields of a User object, build a comma-separated line with them, and write the line to a CSV file:

   @Bean
   @StepScope
   public FlatFileItemWriter<User> writer(@Value("#{jobParameters[fileOut]}") String csvFilePath) {
       BeanWrapperFieldExtractor<User> fieldExtractor = new BeanWrapperFieldExtractor<User>();
       fieldExtractor.setNames(new String[]{"firstName","age"});
   
       DelimitedLineAggregator<User> lineAggregator = new DelimitedLineAggregator<User>();
       lineAggregator.setDelimiter(",");
       lineAggregator.setFieldExtractor(fieldExtractor);
       
       FlatFileItemWriter<User> writer = new FlatFileItemWriter<User>(...