Default intermediate instances for "multi dot delimited" paths? #3669
Replies: 7 comments · 6 replies
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Can you please provide the mapper that have as well? The problem here is that MapStruct has no way of knowing that You might be able to solve it by changing your mapper, but would need to see your existing mapping to be able to help more there |
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Yes, that is the problem. And a pretty general situation. I'd use whatever mapper configuration solves the problem. But I currently use an interface for the Mapping and Mapstruct instantiation: @Mapper(
config = CommonMappingConfig.class,
builder = @Builder(disableBuilder = true),
uses = { CommonMapping.class, DateMapping.class, DimensionedUnitsMapping.class, EnumMapping.class })
public interface LocationMapping {
LocationMapping INSTANCE = newMapper();
static LocationMapping newMapper() {
LocationMapping mapper = Mappers.getMapper(LocationMapping.class);
return mapper;
}
@Mapping(target = "currentLocation.time", source = "createdAt", qualifiedBy = DateTimeGroup.class)
@Mapping(target = "currentLocation.lat", source = "latitude")
@Mapping(target = "currentLocation.lng", source = "longitude")
void fromPojo(PojoLocation pojo, @MappingTarget ModelWithLocation model, @Context LocationMapping_Ctx ctx);
} |
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Thanks for sharing this. Seems like you are doing update mappings and we would try to set some values if the value was null. What you could try (not sure if it'll work) is to add a method like: @Mapping(target = "currentLocation.lng", source = "pojo")
void fromPojo(PojoLocation pojo, @MappingTarget ModelWithLocation model, @Context LocationMapping_Ctx ctx);
@BeanMapping(resultType = PointLocation.class)
@Mapping(target = "time", source = "createdAt", qualifiedBy = DateTimeGroup.class)
@Mapping(target = "lat", source = "latitude")
@Mapping(target = "lng", source = "longitude")
GeoLocation mapToLocation(PojoLocation pojo, @Context LocationMapping_Ctx ctx);This can perhaps avoid the if ( myInstance.currentLocation == null ) {
myInstance.currentLocation = new GeoLocation();
}part of the generated code. |
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Eyeballing that, did you mean to write: @Mapping(target = "currentLocation", source = "pojo")Nice idea. And I can see it working for new instances. However, GeoLocation mapToLocation(PojoLocation pojo, ModelWithLocation model, @Context LocationMapping_Ctx ctx);With handwritten code to check for new or existing GeopLocation instances. And I don't see how that works. Luckily, my LocationMapping_Ctx implementation always stores the current pojo and model instance. And it also can provide all the mapping pairs the pojo and model instances., So I have a "trick" in place that maybe could make this work. But this is quite a bit harder to follow. I'll keep this option in my backpocket. For now, I prefer the ObjectFactory approach as that is simpler. By the way, the reason I use update mapping instead of newInstance mapping is that all my use cases are between networks of connected objects: A list of Pojos becomes a list of Models and vice-versa. We populate both primitive fields and "foreign key" fields ("id" fields to other instances). So all mappings are two-pass: Pass-one instantiates everything, then Pass-two populates all fields and "foreign keys". Synching between pojo and model happens many times, we are always creating and/or updating (also deleting). |
Yes indeed, that's what I meant. Made a typo.
Indeed you are right. It won't fully work for what you need. If the approach with the |
@AfterMapping
default void fromPojo_currentLocation(PojoLocation pojo, @MappingTarget ModelWithLocation model, @Context LocationMapping_Ctx ctx){
if (pojo.createdAt == null && pojo.lat == null && pojo.lng == null){
return;
}
GeoLocation loc = model.getCurrentLocation();
if (loc == null){
loc = new PointLocation(); //can use the subclass because I know the context of the code. Could also delegate to the ctx instance.
model.setCurrentLocation(loc);
}
loc.time = pojo.createdAt;
loc.lat = pojo.lat;
loc.lng = pojo.lng;
} |
class ModelWithLocation{
public GeoLocation getGeoLocationEnsured(){
if (currentLocation == null){
currentLocation = newCurrentLocation(); //internal method. May not know the current context, though
}
return currentLocation;
}
///make the java bean specification happy with a matching setter
public void setGeoLocationEnsured(GeoLocation loc){
setGeoLocation(loc);
}
}And the mapping becomes: Note that this will still create a compile error in I could write a |
Still have the compile error in the LocationMappingImpl class but it will never execute. Disadvantage is that we have to instantiate a PointLocation even if all the pojo fields are null. If that is a real concern then add an AfterMapping method to check for nulls and remove the PointLocation if it has null field values. @BeforeMapping
default void fromPojo_location(PojoLocation pojo, @MappingTarget ModelWithLocation model, @Context LocationMapping_Ctx ctx) {
GeoLocation geo = model.getCurrentLocation();
if (geo == null) {
geo = ctx.newGeoLocation(pojo, model); //let the context decide which subclass to instantiate
model.setCurrentLocation(geo);
}
} |
Add a field to @Mapping(target = "currentLocation.time", source = "createdAt", qualifiedBy = DateTimeGroup.class, pathPopulateBy= CurrentLocationPopulateAnnot.class)
@Mapping(target = "currentLocation.lat", source = "latitude", pathPopulateBy= CurrentLocationPopulateAnnot.class)
@Mapping(target = "currentLocation.lng", source = "longitude", pathPopulateBy= CurrentLocationPopulateAnnot.class)
@Qualifier
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.CLASS)
@interface CurrentLocationPopulateAnnot {}
@CurrentLocationPopulateAnnot
default void currentLocationPopulate(PojoLocation pojo, @MappingTarget ModelWithLocation model, @Context LocationMapping_Ctx ctx){
if (pojo.createdAt == null && pojo.lat == null && pojo.lng == null){
//Aside: This is wishful thinking because even though I use a @Condition method to check for nulls in my standard mapping, will Mapstruct use it for each step along the path?
return;
}
GeoLocation geo = model.getCurrentLocation();
if (geo == null){
geo = ctx.newGeoLocation(pojo, model); //let the context decide which subclass to instantiate
model.setCurrentLocation(geo);
}
} |
Maybe you can try the new (from 1.6)
I haven't tried, but try adding that method with |
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Nice! Had not seen In the meantime, @ObjectFactory
default GeoLocation createGeoLocation(@Context LocationMapping_Ctx ctx) {
// Let the context decide which subclass to instantiate
// Cannot add the PojoLocation or the ModelWithLocation instance to this method, however.
// But luckily, my ctx instance keeps track of the current pojo and model instances so it does not need them.
return ctx.newGeoLocation();
}And the generated LocationMappingImpl changes to: if ( model.getCurrentLocation() == null ) {
model.setCurrentLocation( createGeoLocation( ctx ) );
}This moves me forward. Thank you very much for your help, Filip. Great tool! |
Use a method convention. Add the prefix "new" to the name of the path and write a new method in the LocationMapper interface. MapStruct calls this instead of instantiating GeoLocation itself. GeoLocation newCurrentLocation(PojoLocation pojo, @MappingTarget ModelWithLocation model, @Context LocationMapping_Ctx ctx){
return ctx.newGeoLocation(pojo, model); //let the context decide which subclass to instantiate
} |
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See my previous comment about this with the |
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I am trying to map a source value to a target that "walks" multiple instances. For example, say I am receiving a latitude/longitude from a source and wish to map it to the path
myInstance.currentLocation.latitude. ThecurrentLocationis an intermediate object that may already exist but will have to be instantiated if not.So the java domain classes are:
Mapstruct maps this as follows (roughly; I am simplifying the actual code):
The fatal problem is that it is trying to instantiate the abstract class
GeoLocationinstead of the correct classPointLocation.I know how to solve this by writing my own custom code mapping method, but I wonder if there is a convenient way in mapstruct to control the instantiation of these "intermediate" instances? I cannot find anything in the manual.
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