Map custom method mapper to Mapstruct

Question

I'm creating a poc for using Mapstruct in my future projects.

Now I have one question how to map custom methods to a special target.

For example I have following interface mapper:

@Mapper public interface ItemMapper {      static ItemMapper INSTANCE = Mappers.getMapper(ItemMapper.class);      @Mappings({ @Mapping(source = "number", target = "itemnumber"),             @Mapping(source = "description", target = "description"),             @Mapping(source = "itemClass.name", target = "ic"), @Mapping(source = "optionPart", target = "option"),             @Mapping(source = "plannerCode.code", target = "plannercode"),             @Mapping(source = "plannerCode.name", target = "planner"),             @Mapping(source = "vendor.buyerCode.name", target = "buyer"),             @Mapping(source = "vendor.buyerCode.code", target = "buyerCode"),             @Mapping(source = "vendor.number", target = "vendor"),             @Mapping(source = "vendor.name", target = "vendorName"), @Mapping(source = "pcsItem", target = "pcs"),             @Mapping(source = "specialColourVariant", target = "specialColors"),             @Mapping(source = "qtyBufferGreen", target = "greenLine"),             @Mapping(source = "qtyBufferRed", target = "redine"), @Mapping(source = "leadtime", target = "leadTime"),             @Mapping(source = "qtyStock", target = "stockAC"),             @Mapping(source = "qtyStockSupplier", target = "stockSupplier"),             @Mapping(source = "qtyPurchaseOrder", target = "qtyPo"),             @Mapping(source = "qtyShopOrder", target = "qtySo"),             @Mapping(source = "qtyFirmPlannedOrder", target = "qtyFpo"),             @Mapping(source = "qtyForecast", target = "qtyForecast"),             @Mapping(source = "standardCost", target = "stdCost"),             @Mapping(source = "itemCategory.name", target = "category") })     ItemViewModel itemToDto(Item item);      default String locationToLocationDto(Item item) {         return item.getItemsOnDetailedLocations().iterator().next().getLocation().getLocation();     }      default double locationToBinType(Item item) {         return item.getItemsOnDetailedLocations().iterator().next().getBinType();     }      default double itemToLotsize(Item item) {         double lotSize = 0;         if (item.getLotsize() != null) {             lotSize = item.getLotsize();         } else if (item.getItemsOnDetailedLocations() != null && !item.getItemsOnDetailedLocations().isEmpty()) {             ItemsOnDetailedLocation location = item.getItemsOnDetailedLocations().iterator().next();             lotSize = location.getLotSize();         } else {             lotSize = 0.0;         }         return lotSize;     }      default double stockRails(Item item) {         double value = 0;         for (ItemsOnDetailedLocation detailedLocation : item.getItemsOnDetailedLocations()) {              if (detailedLocation.getId().getSource().equals("RAILS")) {                  long lotSize2 = detailedLocation.getLotSize();                 long binInStock = detailedLocation.getBinInStock();                  if (binInStock != 0) {                      value += lotSize2 * (binInStock - 0.5);                 }             }          }          return value;     }  } 

In the code you can see the mapping and some default methods with other mapping in it. How can I use those methods in the Mapstruct mappings so that mapstruct uses those methods to fillin values in the fields?

Answer 1

As you have multiple default methods that return the same type. You would need to use Mapping method selection based on qualifiers.

What this means is that you would need to write your mapper in the following format:

@Mapper public interface ItemMapper {      // Omitting other mappings for clarity     @Mapping(source = "item", target = "locationDto", qualifiedByName = "locationDto")     @Mapping(source = "item", target = "binType", qualifiedByName = "binType")     @Mapping(source = "item", target = "lotSize", qualifiedByName = "lotSize")     @Mapping(source = "item", target = "stockRails", qualifiedByName = "stockRails")     ItemViewModel itemToDto(Item item);      @Named("locationDto")     default String locationToLocationDto(Item item) {         //Omitting implementation     }      @Named("binType")     default double locationToBinType(Item item) {         //Omitting implementation     }      @Named("lotSize")     default double itemToLotsize(Item item) {         //Omitting implementation     }      @Named("stockRails")     default double stockRails(Item item) {         //Omitting implementation     } } 

Some important notes:

• You need to use @Named from the MapStruct package
• In source you can also specify the name of the parameter of the method
• In qualifiedByName you need to specify the value that you have written in @Named

I would strongly advise against using expressions for such complicated things. It is much more difficult to get it correct and it is more difficult for maintaining

Answer 2

Simplest way is using powerfull mapstruct @AfterMapping annotation. E.g.

@AfterMapping public void treatAdditional(User user, @MappingTarget StudentSkillsTo studentSkillsTo) {     System.out.println("After mapping!"); }