Mapstruct - Prepare a list from a group of fields from the source object and set it to target object

Question

I am getting the following flat structure from mongo db document as in source object and I need to group a few fields based on a pattern to prepare an arraylist and set it to the target object.

{
   "_id": 1,
   "clientId": "1001",
   "grant1Id": "1",
   "grant1Type" : "A",
   "grant1Amount": "100",
   "grant2Id": "2",
   "grant2Type": "B",
   "grant2Amount": "200",
   "grant3Id": "3",
   "grant3Type": "C",
   "grant3Amount": "300",
   .....so on
}

The grant# can go upto 20 objects. So, I want to combine all grant fields and prepare an array.

The output should look like this:

{
    "_id": 1,
   "clientId": "1001",
   "grants": [
    {
     "grantId": "1",
     "grantType" : "A",
     "grantAmount": "100",
    },
    {      
     "grantId": "2",
     "grantType" : "B",
     "grantAmount": "200",
    },
    {
     "grantId": "3",
     "grantType" : "C",
     "grantAmount": "300",
    }
   ]
}

Source object structure:

public class Source {
      private String id;
      private String clientId;
      private String grant1Id;
      private String grant1Type;
      private String grant1Amount;
      ...so on
}

Target object:

public class Target {
      private String id;
      private String clientId;
      private List<Grant> grants;
}

Any help will be appreciated.

Thanks.

Answer 1

You can have an afterMapping method where you can set your Target object.

    @AfterMapping
    default void convertNameToUpperCase(Source source, @MappingTarget Target target) {
        //set grants from source to target
    }