MapStruct-在复杂对象上下文中可迭代到不可迭代

Question

我目前正在面对mapstruct和它的初学者问题，其中一个是以下问题。

我知道示例方案：https://github.com/mapstruct/mapstruct-examples/tree/master/mapstruct-iterable-to-non-iterable

    @Mapping(target = "employee.mainAddress.address", source = "employee.registeredAddresses[0].privateAddresses[0].address")
    abstract EmployeeDto map(Employee employee);

希望对象结构清晰。在源代码中有两个列表，应该为每个列表选择第一个元素。MapStruct如何做到这一点？

Answer 1

只需自己指定一个映射方法。MapStruct可以承担大部分映射代码的负担，但对于某些代码，您只需要稍微帮忙。这就是该示例试图演示的内容。

@Mapper
public abstract class MyMapper{

    @Mapping(target = "employee.mainAddress.address", source = "employee.registeredAddresses")
    abstract EmployeeDto map(Employee employee);
 
    // implement a concrete method yourself that MapStruct can recognise and call in its generated code
    AddressDto map(List<PrivateAddress> source) {

     // perhaps do some NPE checking, call MapStruct generated method below
     return map( source.get(0).get(0) );
  }

  // continue letting MapStruct do the bulk of the work
  abstract AddressDto map(Address source);

}