Ho to use a custom mapper with mapstruct with nested values and conditional values - mapping

Question

I am trying to map one object to another using mapstrut and currently facing some challenges on how to use it for some cases.
public class TargetOrderDto {
String id;
String preferedItem;
List<Item> items;
String status;
Address address;
}
public class Item {
String id;
String name;
}
public abstract class TargetOrderMapper {
#Autowired
private StatusRepository statusRepository;
#Mappings({
#Mapping(target = "id", source = "reference"),
#Mapping(target = "preferedItem", source = ""), // Here I need to loop through these values checking for a single value with a specific tag
#Mapping(target = "items", source = "items"), // List of objects to another list of different data types.
#Mapping(target = "status", source = "remoteStatus") // may need to extract a value from a repository
})
abstract OrderDto toTargetOrderDto(RemoteOrder remoteOrder);
}
// Remote Data
public class RemoteOrder {
String reference;
List<Item> items;
String remoteStatus;
}
public class RemoteItem {
String id;
String flag;
String description;
}
These are the current scenarios that I have failed to get my head around (maybe I am mapping a complex object).
preferedItem :
for this, I need to loop though the items in the order and identify the item with a specific flag. (if it matches then I take that value else I use null)
items :
I need to convert this to a list of 2 different lists; List from List, all have different mapping rules of their own.
remoteStatus :
This one is abit more tricky, I need to extract the status from remoteOrder then lookit up in the db using the statusRepository for an alternate mapped value in db.
any help is highly appreciated.

Answer 1

You can't do business logic with MapStruct. So keep mappings simple and define your own methods were it comes to conditional mappings in list. Note: you can write your own method and MapStruct will select it. Also, from this own implementation you can refer to MapStruct methods again.
public abstract class TargetOrderMapper {
#Autowired
private StatusRepository statusRepository;
#Mappings({
#Mapping(target = "id", source = "reference"),
#Mapping(target = "preferedItem", source = ""), // Here I need to loop through these values checking for a single value with a specific tag
#Mapping(target = "items", source = "items"), // List of objects to another list of different data types.
#Mapping(target = "status", source = "remoteStatus") // may need to extract a value from a repository
})
abstract OrderDto toTargetOrderDto(RemoteOrder remoteOrder);
protected List<Item> toItemList(List<Item> items) {
// do what ever you want..
// and call toItem during iterating.
}
protected abstract Item toItem(Item item);
}
The same goes for status. I added a FAQ entry some time ago about list (mainly about updating, but I guess the same applies here).
About lookups, you can use #MappingContext to pass down a context that contains the logic to access a DB. See here