Remove boilerplates codes when using builder pattern of lombok

Question

I'm using Builder pattern of lombok in my Spring boot project.

@Getters
@SuperBuilder(toBuilder = true)
@NoArgsConstructor
class Parent{
    private String _id;
    private String name;
}

@Getters
@SuperBuilder(toBuilder = true)
@NoArgsConstructor
class child_1 extends Parent{
    private String address;
}   

@Getters
@SuperBuilder(toBuilder = true)
@NoArgsConstructor
class child_2 extends Parent{
    private String gender;
}

When I get the instance of Parent

if(parent instanceof Child_1){
    Child_1 c1=(Child_1) parent;
    
    Parent p=Child_1.builder()._id(c1.get_id()).name(c1.getName()).address(c1.getAddress()).build();
}

else if(parent instanceof Child_2){
    Child_2 c2=(Child_2) parent;
    
    Parent p=Child_2.builder()._id(c2.get_id()).name(c2.getName()).gender(c1.getGender()).build();
}

This is perfectly working. But there are some boilerplate codes like _id(c1.get_id()).name(c1.getName()) . I showed here only _id and name as an example. But I have more than 20 fields in Parent and more than 10 child classes with many fields. So the parent variables are again and again repeating. Is there any way to cut these boilerplate codes?

I tried something like following when I get Parent object. Here p is a Parent object

Parent parent=Parent.builder()._id(p.get_id()).name(p.getName()).build();

if(p instanceof Child_1){
    Child_1 c1=(Child_1) parent;
    
    parent=Child_1.builder().address(c1.getAddress()).build();
}

else if(p instanceof Child_2){
    Child_2 c2=(Child_2) parent;
    
    parent=Child_2.builder().gender(c1.getGender()).build();
}

But this assigning null to parent variables since I assign again to parent object from child classes. Any approaches will be appreciated. thanks in advance

Answer 1

You can use BeanUtils.copyProperties(<Source>, <Target>);

Parent fromChild=null;

if(p instanceof Child_1){
    Child_1 c1=(Child_1) parent;
    
    fromChild=Child_1.builder().address(c1.getAddress()).build();
}

Parent parent=Parent.builder()._id(p.get_id()).name(p.getName()).build();

BeanUtils.copyProperties(parent, fromChild);

fromChild has null values of _id and name . So when we create parent , we can easily overwrite null values