Java API to make an object from a CSV file

Question

I'm looking for a library that allows me to map a .csv contents to an object.

Something like:

public class Person {

    private String name;
    private int age;

    @CsvField("name")
    public String getName() {
        return this.name;
    }

    @CsvField("age")
    public int getAge() {
        return this.age;
    }
}

and then say something like:

final Person filledWithDataFromCsv = csvApi.load(csvFilepath, Person.class);

from the given CSV:

#name, age
tom, 11
jim, 32

Does anyone know of such an API, or one that does something similar. I don't want it to use annotations as a must, I just want to be able to load the file with one line of code and a predefined class.

It should be pretty easy to write one, however something which does it already would be better. I wouldn't use annotations either, I would just use the field names. ;) — Peter Lawrey, Jun 20 '11 at 12:50
@Peter why do you prefer field names over annotations ? I always tend to turn away from the reflection based approaches. — Simeon, Jun 20 '11 at 12:56
@Simeon, You would have to use reflections to get the annotations. Do the annotations add value, otherwise they just make your code more verbose? — Peter Lawrey, Jun 20 '11 at 12:57
@Peter well they decouple your field names from the csv, so you can rename freely. Otherwise if you decide that a new name better fits a given field, but you have already given your CSV format to a client you can no longer change your object member names (not without savage hacking anyway ...) :) — Simeon, Jun 20 '11 at 13:02
@simeon With annotations won't you need to tag your setter fields as well as your getter fields? — Atreys, Jun 20 '11 at 13:02
@Simeon, If you make that change you are better off defining the mapping externally, other wise you can only have one mapping for all versions of a file type ever. — Peter Lawrey, Jun 20 '11 at 13:04
@Atreys no, you can either tag setters, getters or fields depending on preference. Hibernate/JPA uses the getters. — Simeon, Jun 20 '11 at 13:06

score 26 · Accepted Answer · answered Jun 20 '11 at 12:56

JSefa allow you to annotate Java classes that can be used in a serialization and de-serialization process. The tutorial demonstrates how this works with the CsvIOFactory class.

(From the tutorial) Annotating a bean is as simple as specifying the locations of the items in the list of values, and if necessary, you'll need to specify the conversion format:

@CsvDataType()
public class Person {
    @CsvField(pos = 1)
    String name;

    @CsvField(pos = 2, format = "dd.MM.yyyy")
    Date   birthDate;
}

@VineetReynolds can we use it without postion, i mean with the help of columnName? — Govind Singh, Aug 24 '15 at 09:55

score 12 · Answer 2 · answered Jun 20 '11 at 12:52

12

I prefer opencsv, it is ultra simple and very clean.

http://opencsv.sourceforge.net/

For example reading:

CSVReader reader = new CSVReader(new FileReader("yourfile.csv"));
String [] nextLine;
while ((nextLine = reader.readNext()) != null) {
    // nextLine[] is an array of values from the line
    System.out.println(nextLine[0] + nextLine[1] + "etc...");
}

answered Jun 20 '11 at 12:52

Thomas Jungblut

20,854
6
68
91

2

Your example does not map to a java bean with annotations. – Jeronimo Backes May 05 '15 at 09:56
1

See here for how to do it with open csv http://stackoverflow.com/a/14976689/1000011 – opticyclic Oct 30 '15 at 18:03
2

+ one to this, opencsv is more up to date as of 2020 – Mehdi LAMRANI May 23 '20 at 22:23

score 11 · Answer 3 · edited Dec 10 '15 at 05:30

11

You can't go wrong with uniVocity-parsers. It supports all sorts of powerful operations and it is much faster than any other CSV parser for Java.

Here's a class with some examples:

class TestBean {

    // if the value parsed in the quantity column is "?" or "-", it will be replaced by null.
    @NullString(nulls = { "?", "-" })
    // if a value resolves to null, it will be converted to the String "0".
    @Parsed(defaultNullRead = "0")
    private Integer quantity;   // The attribute type defines which conversion will be executed when processing the value.

    @Trim
    @LowerCase
    // the value for the comments attribute is in the column at index 4 (0 is the first column, so this means fifth column in the file)
    @Parsed(index = 4)
    private String comments;

    // you can also explicitly give the name of a column in the file.
    @Parsed(field = "amount")
    private BigDecimal amount;

    @Trim
    @LowerCase
    // values "no", "n" and "null" will be converted to false; values "yes" and "y" will be converted to true
    @BooleanString(falseStrings = { "no", "n", "null" }, trueStrings = { "yes", "y" })
    @Parsed
    private Boolean pending;
}

Here's how to get a list of TestBean

BeanListProcessor<TestBean> rowProcessor = new BeanListProcessor<TestBean>(TestBean.class);

CsvParserSettings parserSettings = new CsvParserSettings();
parserSettings.setRowProcessor(rowProcessor);
parserSettings.setHeaderExtractionEnabled(true);

CsvParser parser = new CsvParser(parserSettings);
parser.parse(getReader("/examples/bean_test.csv"));

List<TestBean> beans = rowProcessor.getBeans();

Disclosure: I am the author of this library. It's open-source and free (Apache V2.0 license).

edited Dec 10 '15 at 05:30

josliber

43,891
12
98
133

answered May 05 '15 at 09:57

Jeronimo Backes

6,141
2
25
29

`getReader` is not defined? – Govind Singh Aug 24 '15 at 11:27
Just use new FileReader(new File("path/to/file.csv")); – Jeronimo Backes Aug 24 '15 at 15:15
Can JeronimoBackes or @josliber answer this one please: http://stackoverflow.com/questions/36647873/need-to-map-multiple-columnames-to-a-single-field-in-univocity – Koustav Ray Apr 15 '16 at 16:00
I see an Apache License version of the project at https://github.com/uniVocity/univocity-parsers/# but see an entirely different site that talks about it being free for non-commerical use http://www.univocity.com/products/license Can you clarify the differences between the Apache version and the version on the univocity.com site? – Sanjiv Jivan May 16 '16 at 16:16
Univocity-parsers is free. The univocity framework is commercial. – Jeronimo Backes May 16 '16 at 19:23
@JeronimoBackes i was trying to use it but readOrder was null for me at BeanConversionProcessor - and rowProcessor.getBeans() came back as null. what can i do to fix it ? – 2Big2BeSmall Jun 14 '17 at 09:39
1

This answer should be accepted as the best answer, especially the `map field by header name` feature. I can't find the same feature in other CSV parser. – min Mar 28 '18 at 07:53
1

This seriously needs to be voted up. I spent all day trying to use JSEFA pulling my hair out trying to get it to work, and then I found this and had it running like clockwork within 10 minutes! Thank you for your great work! – Daryn May 16 '18 at 06:46

score 4 · Answer 4 · answered Jun 20 '11 at 12:54

4

There are pretty good JDBC implementations for CSV. So you can make use of such a driver, configure a datasource to use it and then use JPA (or whatever) for object-relational mapping on top of that data source.

answered Jun 20 '11 at 12:54

Costi Ciudatu

37,042
7
56
92

user3996996 · Answer 5 · 2019-09-12T13:03:14.930

3

SimpleFlatMapper can do that easily see Getting Started csv using the headers of the csv or by manually specifying which columns map to what property.

CsvParser
    .mapTo(MyObject.class)
    .forEach(file, System.out::println);

edited Sep 12 '19 at 13:03

answered Sep 26 '14 at 09:27

user3996996

342
3
5

Java API to make an object from a CSV file

5 Answers5

Linked

Related