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这是我的示例设置：

interface EnumMessage {
  boolean carrier(String message);

  String getValue();

  default String getMessage() {
    return getValue().toUpperCase();
  }
}

enum EnumMessageA implements EnumMessage {
  GREAT("You are doing great"),
  GOOD("You are doing good"),
  OK("You are doing ok");

  private String value;

  EnumMessageA(final String value) {
    this.value = value;
  }

  @Override
  public String getValue() {
    return value;
  }

  @Override
  public boolean carrier(final String message) {
    return this.value.equals(message);
  }
}

class SourceX {
  public String name;
  public String message;
}

class TargetX {
  public String name;
  public EnumMessageA messageA;
}

@Mapper
interface EnumMapper {
  EnumMapper INSTANCE = Mappers.getMapper(EnumMapper.class);

  @Mapping(source = "message", target = "messageA", qualifiedByName = "stringToEnum")
  TargetX toTarget(SourceX source);

  @Mapping(source = "messageA", target = "message", qualifiedByName = "enumToString")
  SourceX toSource(TargetX target);

  @Named("stringToEnum")
  default <T extends EnumMessage> T mapStringToEnum(
      final String message, @TargetType final Class<T> enumClass) {
    final T[] values = enumClass.getEnumConstants();
    return Arrays.stream(values)
        .filter(enumValue -> enumValue.carrier(message))
        .findFirst()
        .orElse(null);
  }

  @Named("enumToString")
  default <T extends EnumMessage> String mapEnumToString(final T enumValue) {
    return enumValue.getMessage();
  }
}

我无法通过考试。

 public class EnumMapperTest {
    
      @Test
      void checkMapping() {
        TargetX target = new TargetX();
        target.name = "MapStructTesting";
        target.messageA = EnumMessageA.GREAT;
        Assertions.assertEquals(
            "You are doing great".toUpperCase(), EnumMapper.INSTANCE.toSource(target).message);
    
        SourceX source = new SourceX();
        source.name = "MapStructTesting";
        source.message = "You are doing ok";
        Assertions.assertEquals(EnumMessageA.OK, EnumMapper.INSTANCE.toTarget(source).messageA);
      }
    }

我尝试使用或不使用qualifiedByName，但无法让 MapStruct 使用该mapStringToEnum方法。

我不确定这是否是 MapStruct 中的一个错误，在使用时无法使用 Enum 继承，@TargetType或者我遗漏了一些东西。

  • 使用@Mapping(source = "message", target = "messageA", qualifiedByName = "stringToEnum")时，会出现编译时错误：
    error: Qualifier error. No method found annotated with @Named#value: [ stringToEnum ]. See https://mapstruct.org/faq/#qualifier for more info.
      @Mapping(source = "message", target = "messageA", qualifiedByName = "stringToEnum")
     error: Can't map property "String message" to "EnumMessageA messageA". Consider to declare/implement a mapping method: "EnumMessageA map(String value)".
      @Mapping(source = "message", target = "messageA", qualifiedByName = "stringToEnum")
  • 当使用@Mapping(source = "message", target = "messageA")或与 resultType 一起使用时@Mapping(source = "message", target = "messageA", resultType = EnumMessage.class，生成的实现会忽略提供的方法。
class EnumMapperImpl implements EnumMapper {

    @Override
    public TargetX toTarget(SourceX source) {
        if ( source == null ) {
            return null;
        }

        TargetX targetX = new TargetX();

        if ( source.message != null ) {
            targetX.messageA = Enum.valueOf( EnumMessageA.class, source.message );
        }
        targetX.name = source.name;

        return targetX;
    }

    @Override
    public SourceX toSource(TargetX target) {
        if ( target == null ) {
            return null;
        }

        SourceX sourceX = new SourceX();

        sourceX.message = mapEnumToString( target.messageA );
        sourceX.name = target.name;

        return sourceX;
    }
}

如果有更优雅的方法来概括映射，我愿意接受建议。注意：我不能使用 ，@BeforeMapping / @AfterMapping因为我有许多要映射的枚举类型，因此寻找隐式或通用的解决方案。

4

1 回答 1

2

想通了，并在GitHub 上向 MapStruct 团队提出了一个错误。

要使其正常工作，必须满足以下条件：

  1. 映射器方法必须是static
  2. qualifiedByName属性当然是必需的，即使我将通用签名更改为<T extends Enum<T> & EnumMessage>

所以我修改后的代码是这样的：

@Mapper
public class EnumMapperHelper {

  @Named("stringToEnum")
  public static <T extends EnumMessage> T mapStringToEnum(
      final String message, @TargetType final Class<T> enumClass) {
    final T[] values = enumClass.getEnumConstants();
    return Arrays.stream(values)
        .filter(enumValue -> enumValue.carrier(message))
        .findFirst()
        .orElse(null);
  }

  @Named("enumToString")
  //this doesn't have to be static but yes the @Qualifier is required
  public static <T extends EnumMessage> String mapEnumToString(final T enumValue) {
    return enumValue.getMessage();
  }
}


@Mapper(uses = EnumMapperHelper.class) 
interface EnumMapper {
  EnumMapper INSTANCE = Mappers.getMapper(EnumMapper.class);

  @Mapping(source = "message", target = "messageA", qualifiedByName = "stringToEnum")
  TargetX toTarget(SourceX source);

  @Mapping(source = "messageA", target = "message", qualifiedByName = "enumToString")
  SourceX toSource(TargetX target);
}
于 2021-05-28T05:38:28.957 回答