OpenCSV, how to write into csv with custom processing?

Question

I am trying to write List of POJO objects into a csv. I use opencsv and the code is very minimal:

 StatefulBeanToCsv sbc = new StatefulBeanToCsvBuilder(writer)
                    .withSeparator(CSVWriter.DEFAULT_SEPARATOR)
                    .build();

I use Custom converters while reading, can I do something similar for write also? For e.g.:

1. if field is of type List, it gets written as "[a,b]". But I would like to do something like this: "a,b".
2. A field is of type LocalDataTime, I would like to write it in the format "MM/dd/yyyy" and discard time completely in the output csv.

I want output to be something like this:

date of issue,items
"02/22/2020","a,b"

Instead of:

date of issue,items
"2020-02-22T00:00","[a,b]"

Thank you so much, appreciate any help :)

Answer 1

You can use the annotations @CsvDate for set custom date format and @CsvBindAndSplitByName for the conversion of the list to string. Please find below example:

import static java.time.temporal.ChronoUnit.MONTHS;

import com.opencsv.CSVWriter;
import com.opencsv.bean.CsvBindAndSplitByName;
import com.opencsv.bean.CsvBindByName;
import com.opencsv.bean.CsvDate;
import com.opencsv.bean.StatefulBeanToCsv;
import com.opencsv.bean.StatefulBeanToCsvBuilder;


import java.io.FileWriter;
import java.io.Writer;
import java.time.LocalDateTime;
import java.util.List;

public class Main {

    public static void main(String[] args) throws Exception {

        Writer writer = new FileWriter("example.csv");

        StatefulBeanToCsv<Item> sbc = new StatefulBeanToCsvBuilder<Item>(writer)
                .withSeparator(CSVWriter.DEFAULT_SEPARATOR)
                .build();

        List<Item> items = List.of(
                new Item(LocalDateTime.now().minus(4, MONTHS), List.of("1", "s")),
                new Item(LocalDateTime.now().minus(1, MONTHS), List.of("1", "d")),
                new Item(LocalDateTime.now().minus(3, MONTHS), List.of("1", "2", "3"))
        );
        sbc.write(items);

        writer.close();


    }

    public static class Item {

        @CsvBindByName(column = "date")
        @CsvDate(value = "yyyy-MM-dd'T'hh:mm")
        private LocalDateTime date;

        @CsvBindAndSplitByName(column = "list", elementType = String.class, writeDelimiter = ",")
        private List<String> array;

        Item(LocalDateTime date, List<String> array) {
            this.date = date;
            this.array = array;
        }

        public LocalDateTime getDate() {
            return date;
        }

        public void setDate(LocalDateTime date) {
            this.date = date;
        }

        public List<String> getArray() {
            return array;
        }

        public void setArray(List<String> array) {
            this.array = array;
        }
    }
}

The output of example.csv:

"DATE","LIST"
"2020-03-10T02:37","1,s"
"2020-06-10T02:37","1,d"
"2020-04-10T02:37","1,2,3"