在Mapstruct中使用Vavr列表:没有为返回类型io.vavr.collection.List注册实现类型。

Question

我试图在一个具有Vavr列表的对象上使用Mapstruct。

但是我得到了错误java: No implementation type is registered for return type io.vavr.collection.List，但是在java.util.List上工作得很好。

几年前，我看到了关于"Page“数据类型Mapstruct return type的另一个问题，它有类似的错误，但我没有看到任何更新。

没有解决办法吗？在调用对象上的mapstruct mapper时，我可以将vavr列表更改为Java列表，反之亦然，但是如果对象有具有vavr列表的子对象，那么我不确定可以做什么，因为在mapstruct mapper文件中，我什么都不能做。

我正在使用最新的mapstruct版本：

      <dependency>
            <groupId>org.mapstruct</groupId>
            <artifactId>mapstruct</artifactId>
            <version>1.4.2.Final</version>
        </dependency>
        <dependency>
            <groupId>org.mapstruct</groupId>
            <artifactId>mapstruct-processor</artifactId>
            <version>1.4.2.Final</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok-mapstruct-binding</artifactId>
            <version>0.2.0</version>
        </dependency>

ParentObject：

import io.vavr.collection.List;
import lombok.Builder;
import lombok.Data;

@Data
@Builder
public class ParentObject {
    private String parentField;

    private List<ParentInnerObject> parentInnerObjectList;

ParentInnerObject：

@Data
@Builder
public class ParentInnerObject {
    private String parentInnerField;

ChildObject：

import io.vavr.collection.List;
import lombok.Builder;
import lombok.Data;

@Data
@Builder
public class ChildObject {
    private String childField;

    private List<ChildInnerObject> childInnerObjectList;

ChildInnerObject：

@Data
@Builder
public class ChildInnerObject {
    private String childInnerField;

示例映射器将ParentObject映射到ChildObject：

@Mapper(componentModel = "spring", unmappedTargetPolicy = ReportingPolicy.WARN)
public abstract class TestMapper {

    @Mapping(source = "parentField", target = "childField")
    @Mapping(source = "parentInnerObjectList", target = "childInnerObjectList")
    public abstract ChildObject toChildObject(final ParentObject parentObject);

    public abstract List<ChildInnerObject> toChildObjects(
            final List<ParentInnerObject> parentInnerObjectList);

    @Mapping(source = "parentInnerField", target = "childInnerField")
    public abstract ChildInnerObject toChildInnerObject(final ParentInnerObject parentInnerObject);

测试类以测试映射程序代码：

import io.vavr.collection.List;

@ExtendWith(MockitoExtension.class)
class TestMapperTest {
  //https://stackoverflow.com/questions/34067956/how-to-use-injectmocks-along-with-autowired-annotation-in-junit
  @Autowired
  @InjectMocks
  private TestMapperImpl testMapper;

  @Test
  @DisplayName("Check if the value is returned correctly")
  void testMapperCode(){
    ParentObject pa = ParentObject.builder()
            .parentField("parent field")
            .parentInnerObjectList(List.of(ParentInnerObject.builder()
                    .parentInnerField("parent inner field")
                    .build()))
            .build();
    /*ParentObject pa = ParentObject.builder()
            .parentField("parent field")
            .parentInnerObjectList(Collections.singletonList(ParentInnerObject.builder()
                    .parentInnerField("parent inner field")
                    .build()))
            .build();*/
    ChildObject childObject = testMapper.toChildObject(pa);
    System.out.println(childObject);
  }

}

编辑：-现在使用自定义映射程序，直到mapstruct中支持vavr列表。

import io.vavr.collection.Iterator;
import io.vavr.collection.List;

@Mapper(componentModel = "spring", unmappedTargetPolicy = ReportingPolicy.WARN)
public abstract class TestMapper {
    @Mapping(source = "parentField", target = "childField")
    //@Mapping(source = "parentInnerObjectList", target = "childInnerObjectList") //This does not work as Mapstruct does not support Vavr list yet
    @Mapping(target = "childInnerObjectList", expression = "java(vavrListSetter(parentObject.parentInnerObjectList))") //custom mapper
    public abstract ChildObject toChildObject(final ParentObject parentObject);

    @Mapping(source = "parentInnerField", target = "childInnerField")
    public abstract ChildInnerObject toChildInnerObject(final ParentInnerObject parentInnerObject);

    public List<ChildInnerObject> vavrListSetter(final List<ParentInnerObject> parentInnerObjectList) {
        if (parentInnerObjectList == null) {
            return null;
        }
        return Iterator.ofAll(parentInnerObjectList)
                .map(this::toChildInnerObject)
                .collect(List.collector());
    }

Answer 1

Spring数据页数据类型与Vavr列表不同。需要将Page数据类型视为bean而不是可迭代的，这将在即将发布的1.5版中得到修正。

至于Vavr列表，MapStruct现在不支持使用它。您可以提出一个特性请求，这样我们就可以讨论潜在的解决方案。

目前，唯一的方法是编写自定义映射方法，以便在这些列表之间进行映射。