Support for collection fields

[eximius313]

I have a class:

public class Person {
    @CsvColumn(columnName = "name")
    private String name;
    
    @CsvColumn(columnName = "phones")
    private List<String> phones;
}

where phones could have 0...* elements;

I'd expect that such data (in JSON for readability):

[{ name: "Foo", phones: ["11"] }, { name: "Foo", phones: ["22", "23"] }, { name: "Foo", phones: [] }]

transformed by this code:

CsvProcessor<Person > csvProcessor = new CsvProcessor<>(Person .class);
File csvFile = new File("people.csv");
csvProcessor.writeAll(csvFile, list, true);

should output something like this:

name,phones/0,phones/1
Foo,11,
Foo,22,23
Foo,,

exactly like this tool https://konklone.io/json/ does it

but it throws:

java.lang.IllegalArgumentException: No converter available for type: interface java.util.List
	at com.j256.simplecsv.processor.ColumnInfo.fromAnnoation(ColumnInfo.java:242)
	at com.j256.simplecsv.processor.ColumnInfo.fromAnnotation(ColumnInfo.java:219)
	at com.j256.simplecsv.processor.CsvProcessor.addColumnInfo(CsvProcessor.java:1183)
	at com.j256.simplecsv.processor.CsvProcessor.configureEntityClass(CsvProcessor.java:1017)
	at com.j256.simplecsv.processor.CsvProcessor.checkEntityConfig(CsvProcessor.java:997)
	at com.j256.simplecsv.processor.CsvProcessor.writeAll(CsvProcessor.java:414)
	at com.j256.simplecsv.processor.CsvProcessor.writeAll(CsvProcessor.java:398)

Could you please support collections in SimpleCSV?
One solution is that @CsvColumn could have boolean parameter collectionValues (because names can be generated using name as a base)

Kind regards

[j256]

Hrmm. Interesting idea. Thanks for it.

So would this list/array enabled field be just for the last one? So the last one can be effectively a ... field or something? name,phones... or something?

[eximius313]

I think that it could be in any order.
While writing - it does not matter - you just need to reserve constant quantity of columns equal to max(row1.list.size, row2.list.size, ...).

While reading - you can constrain column name pattern like name/N and then collect N columns as Set

[hatim-heffoudhi]

Hello,
I like the idea, maybe the output can be specified by a delimiter in the annotation :

@CsvColumn(columnName = "phones", delimiter ="-")
 private List<String> phones;

name,phones
Foo,11
Foo,22-23
Foo,11-99-88
Foo,

[j256]

Pretty nice solution @hatim-heffoudhi ! Thanks.