java - ModelMapper - 如何从源计算值并将其设置为目标

Question

我正在尝试使用 ModelMapper 将源映射到目标。

在我的具体情况下，在源类中有一个属性(评论列表)，我必须在其中按评级求和并将该值设置为目标类。

所以我尝试使用转换器，但它不起作用。

        Converter<List<Review>, Double> sumReviewsRating = new AbstractConverter<List<Review>, Double>() {
        @Override
        protected Double convert(List<Review> reviews) {
            if(reviews!=null){
                return reviews.stream().mapToDouble(Review::getRating).sum();
                //it doesn't work also with return 1.0 for example;
            }else{
                return 0.0;
            }
        }
    };

 modelMapper.typeMap(MySource.class, MyDestination.class).addMappings(mapper ->{
            mapper.map(MySource::getCoverImageId, MyDestination::setImageUrl); //this works
            mapper.using(sumReviewsRating).map(MySource::getReviews, MyDestination::setRating);
        });

堆栈跟踪:

org.modelmapper.internal.ErrorsException: null
    at org.modelmapper.internal.Errors.toException(Errors.java:254) ~[modelmapper-2.3.6.jar:na]
    at org.modelmapper.internal.ReferenceMapExpressionImpl.map(ReferenceMapExpressionImpl.java:71) ~[modelmapper-2.3.6.jar:na]
    at org.modelmapper.internal.ConfigurableConditionExpressionImpl.map(ConfigurableConditionExpressionImpl.java:65) ~[modelmapper-2.3.6.jar:na]

如果我在转换器中放置断点，它就不会进入。

我的赌注在哪里？

Answer 1

以下内容对我有用:

ModelMapper modelMapper = new ModelMapper();

Converter<List<String>, Double> sumReviewsRating = new AbstractConverter<List<String>, Double>() {
      @Override
      protected Double convert(List<String> reviews) {
        if(reviews!=null){
          return 1.0;
          //it work also with return 1.0 for example;
        }else{
          return 0.0;
        }
      }
    };

    modelMapper.typeMap(MySource.class, MyDestination.class).addMappings(mapper ->{
      mapper.using(sumReviewsRating).map(MySource::getReview, MyDestination::setRating);
    });

    MySource mySource = new MySource();
    mySource.setReview(Arrays.asList(new String[]{"1","2"}));
    MyDestination destination = modelMapper.map(mySource,MyDestination.class);

    System.out.println(destination.getRating());

类(class)

@Getter @Setter
public class MyDestination {
  Double rating;
}


@Getter @Setter
public class MySource {
  List<String> review;
}

上面的代码成功完成了转换。

尝试添加多个这样的映射

**

typeMap.addMappings(mapper -> mapper.<String>map(Src::getA, Dest::setB))
          .addMappings(mapper -> mapper.<String>skip(Dest::setB))

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