Dozer can be used as an Assembler . Martin Fowler has a great explanation of why and when you would use an Assembler . Basically, it is a way to take multiple fine grain objects and create one coarse grain object used for data transfer. As long as you have mappings defined for each of your fine grained objects to your coarse grain object you can call the mapper multiple times to achieve the desired assembler pattern.
Let's say that ClassA, ClassB, and ClassC all map to ClassD. First create these individual mappings in the mapping file. Next, call the mapper once for each mapping. Note that this would also work in a bi-directinonal manner.
ClassD d = new ClassD(); mapper.map(sourceA, d); mapper.map(sourceB, d); mapper.map(sourceC, d);