Bean Mapping

Many CSV libraries come with built-in support for mapping CSV records to Java beans. While this is a convenient feature, the reflection-based approach used by most libraries comes with a heavy performance penalty, which contradicts FastCSV’s design goal of being fast.

Thanks to Java stream mapping, FastCSV can provide similar functionality without sacrificing performance.

Example

The following example demonstrates how to map CSV records to Java beans using FastCSV.

import java.io.IOException;
import java.util.stream.Stream;

import de.siegmar.fastcsv.reader.CsvReader;
import de.siegmar.fastcsv.reader.NamedCsvRecord;

/// Example for reading CSV data with a mapping function.
///
/// FastCSV supports Java 17 and later, but this code uses Java 25
/// for brevity, leveraging newer language features.
void main() throws IOException {
    try (var persons = readPersons()) {
        persons.forEach(IO::println);
    }
}

Stream<Person> readPersons() throws IOException {
    final String data = """
        ID,firstName,lastName
        1,John,Doe
        2,Jane,Smith
        """;

    try (var csv = CsvReader.builder().ofNamedCsvRecord(data)) {
        return csv.stream().map(this::mapPerson);
    }
}

Person mapPerson(final NamedCsvRecord rec) {
    return new Person(
        Long.parseLong(rec.getField("ID")),
        rec.getField("firstName"),
        rec.getField("lastName")
    );
}

record Person(long id, String firstName, String lastName) {
}

You also find this source code example in the FastCSV GitHub repository.