title: MapStruct: Fields from Different Entities mapping to Same Entity Different fields
body: <p>I have Class A, B and C. Class A has three variables and it gets populated based on different fields of Class B and C. When I use mapper to populate object only last used mapper values are retained. How can I make sure that all values are populated.
      I am using MapStruct mapper(version 1.2.0) with Spring Boot version 2.0.3</p>
  
  <pre><code>Sample code below:
  Class A{
  
    String a;
    String b;
    String c;
  
    }
  
  Class B{
   String b1;
  }
  
  Class C{
      String c1;
  }
  
  public interface AtoCmapper{
    @Mappings({
        @Mapping(target="c", source="source.c1")
    })
    A CtoA(C source);
  
    @Mappings({
        @Mapping(target="c1", source="source.c")
    })
    C AtoC(A source);
  }
  
  public interface AtoBmapper{
    @Mappings({
        @Mapping(target="b", source="source.b1")
    })
    A BtoA(B source);
  
    @Mappings({
        @Mapping(target="b1", source="source.b")
    })
    B AtoB(A source);
  }
  
  Class DAO{
  
   @Autowired
   AtoBmapper aToBMapper;
  
   @Autowired
   AtoCmapper aToCMapper;
  
   public void testMapping(){
    A aObject = new A();
  
    aObject = aToBMapper(bObject); // Assume bObject is object to Type B and it is initialized properly
  
    aObject = aToCMapper(cObject); // Assume cObject is object to Type B and it is initialized properly
   }
  
   //Now when I call testMapping() resulting A object only has value set for variable c, value of b is lost.
   How can I make sure that Values from B and C are set properly to Class A
  }
  </code></pre>