title: Conditional maping in mapstruct
body: <p>i have dto from jackson and its update database with orm hibernate :</p>
  
  <pre><code>class dto {
  
  string f1;
  bool isModifiedF1;
  
  string f2;
  bool isModifiedF2;
  
  setF1(str s) {
  this.isModifiedF1 = true;
  this.f1 = s;
  }
  
  setF2(str s) {
  this.isModifiedF2 = true;
  this.f2 = s;
  }
  
  //othre setter like that
  }
  </code></pre>
  
  <p>i like to hava thigs like this :</p>
  
  <pre><code>classMpperImpl {
  
  modify(dto , entity) {
  
  if(dto.isModifedF1){
  entity.setF1(dto.getF1);
  }
  
  if(dto.isModifedF2){
  entity.setF1(dto.getF2);
  }
  
  //and other method
  
  }
  
  
  }
  </code></pre>
  
  <p>how to do that ?
  i locking soulotion to work with all field and for now i just ignore that important field i need and set it manally with @AfterMapping
  i need to avoid any not chaged field in hibernate like casade create field ...</p>
  
  <p>thank you</p>