I did endup doing my own AbstractConverter please find it below:
It has some constraints which are suitable for me (possibly not for you).
- will update based on "sameId" implementation
- will remove orphans (element from destination not in the source).
- Only works on List (enough for my needs).
- While the converter will manage the decision to update the mapping of objects are delegated back to Dozer so you don't need to implement the mapping of the elements in your list
Sample use
public class MyConverter extends AbstractListConverter<ClassX,ClassY>{
public MyConverter(){ super(ClassX.class, ClassY.class);}
@Override
protected boolean sameId(ClassX o1, ClassY o2) {
return // your custom comparison here... true means the o2 and o1 can update each other.
}
}
Declaration in mapper.xml
<mapping>
<class-a>x.y.z.AClass</class-a>
<class-b>a.b.c.AnotherClass</class-b>
<field custom-converter="g.e.MyConverter">
<a>ListField</a>
<b>OtherListField</b>
</field>
</mapping>
public abstract class AbstractListConverter<A, B> implements MapperAware, CustomConverter {
private Mapper mapper;
private Class<A> prototypeA;
private Class<B> prototypeB;
@Override
public void setMapper(Mapper mapper) {
this.mapper = mapper;
}
AbstractListConverter(Class<A> prototypeA, Class<B> prototypeB) {
this.prototypeA = prototypeA;
this.prototypeB = prototypeB;
}
@Override
public Object convert(Object destination, Object source, Class<?> destinationClass, Class<?> sourceClass) {
if (destinationClass == null || sourceClass == null || source == null) {
return null;
}
if (List.class.isAssignableFrom(sourceClass) && List.class.isAssignableFrom(destinationClass)) {
if (destination == null || ((List) destination).size() == 0) {
return produceNewList((List) source, destinationClass);
}
return mergeList((List) source, (List) destination, destinationClass);
}
throw new Error("This specific mapper is only to be used when both source and destination are of type java.util.List");
}
private boolean same(Object o1, Object o2) {
if (prototypeA.isAssignableFrom(o1.getClass()) && prototypeB.isAssignableFrom(o2.getClass())) {
return sameId((A) o1, (B) o2);
}
if (prototypeB.isAssignableFrom(o1.getClass()) && prototypeA.isAssignableFrom(o2.getClass())) {
return sameId((A) o2, (B) o1);
}
return false;
}
abstract protected boolean sameId(A o, B t);
private List mergeList(List source, List destination, Class<?> destinationClass) {
return (List)
source.stream().map(from -> {
Optional to = destination.stream().filter(search -> same(from, search)).findFirst();
if (to.isPresent()) {
Object ret = to.get();
mapper.map(from, ret);
return ret;
} else {
return create(from);
}
}
).collect(Collectors.toList());
}
private List produceNewList(List source, Class<?> destinationClass) {
if (source.size() == 0) return source;
return (List) source.stream().map(o -> create(o)).collect(Collectors.toList());
}
private Object create(Object o) {
if (prototypeA.isAssignableFrom(o.getClass())) {
return mapper.map(o, prototypeB);
}
if (prototypeB.isAssignableFrom(o.getClass())) {
return mapper.map(o, prototypeA);
}
return null;
}
}