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Java - how to read CSV file into java object using Jackson CSV library?

5 points
Created by:
AnnLen
1777

1. Overview

In this post we will read CSV file into java pojo object using Jackson CSV processor.

To use Jackson CSV library we need to add jackson-dataformat-csv dependency to pom.xml.

<dependency>
    <groupId>com.fasterxml.jackson.dataformat</groupId>
    <artifactId>jackson-dataformat-csv</artifactId>
    <version>2.9.9</version>
</dependency>

2. Read CSV file into java object

Below we have all classes we need to read csv file. Ensure to create csv file on your disc and set correct path in UserCsvReader class.

To run this example copy to your project those 3 files:

  1. UserCsvReader
  2. UserDto
  3. users.csv

2.1 Logic

Logic which reads CSV file into java UserDto pojo object with Jackson CSV library.

Usage of classes:

  • CsvMapper + CsvSchema from jackson CSV library
  • MappingIterator from jackson databind library
import com.fasterxml.jackson.databind.MappingIterator;
import com.fasterxml.jackson.dataformat.csv.CsvMapper;
import com.fasterxml.jackson.dataformat.csv.CsvSchema;

import java.io.File;
import java.io.IOException;
import java.util.List;

public class UserCsvReader {

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

        // set correct path to csv file on your disc
        File csvFile = new File("C:\\csv_tests\\users.csv");

        CsvMapper csvMapper = new CsvMapper();

        CsvSchema csvSchema = csvMapper
                .typedSchemaFor(UserDto.class)
                .withHeader()
                .withColumnSeparator(',')
                .withComments();

        MappingIterator<UserDto> usersIter = csvMapper
                .readerWithTypedSchemaFor(UserDto.class)
                .with(csvSchema)
                .readValues(csvFile);

        List<UserDto> users = usersIter.readAll();

        users.forEach(System.out::println);
    }
}

Output:

UserDto{id=1, name='Ann', age=30}
UserDto{id=2, name='Seth', age=25}
UserDto{id=3, name='Tom', age=27}

2.2 User Pojo object - UserDto

import com.fasterxml.jackson.annotation.JsonPropertyOrder;

@JsonPropertyOrder({"id", "name", "age"})
public class UserDto {

    private Long id;
    private String name;
    private Integer age;

    public UserDto() {

    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "UserDto{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

2.3 User CSV file

Save this file on disc as 'users.csv' and change location in UserCsvReader class.

id,name,age
1,Ann,30
2,Seth,25
3,Tom,27

References

  1. jackson-dataformat-csv - maven
  2. Comma-separated values (CSV) - wiki
  3. CsvMapper - JavaDoc
  4. CsvSchema - JavaDoc
  5. MappingIterator - JavaDoc
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