如何在 Spring Data Rest 中添加特定字段? [英] How to add a specific field in Spring Data Rest?

问题描述

我正在使用 Spring Data Rest 开发 Web 服务.

I am developing a web service using Spring Data Rest.

public interface BookRepository extends PagingAndSortingRepository<Book, Long> {

    @Override
    @Query("select avg(rl.rating) as rating, b from ReadingList rl join rl.book b group by rl.book order by rating desc")
    Page<Book> findAll(Pageable pageable);
}

当我在 JPQL 中选择如上时，'avg (rl.rating) as rating' 列没有如下图所示的名称.

When I select in JPQL as above, 'avg (rl.rating) as rating' column does not have the name like the image below.

在此处输入图片描述

评分:4.0
我想做这项服务.

rating: 4.0
I would like to do this service.

另外，完整源码在github.https://github.com/ohgamja3/readinglist-rest-server/

In addition, the full source is in github. https://github.com/ohgamja3/readinglist-rest-server/

我需要有关此问题的帮助.感谢阅读.

I would like help with this issue. Thanks for reading.

推荐答案

您可以使用 projection 在您的 repo 方法的输出中.

You can use projection in the output of your repo method.

1. 因此，在您的情况下，您可以设置投影，例如:

@Projection(name = "BookWithRating", types = { Book.class }) 
interface BookWithRating { 

  Float getRating(); 

  Book getBook(); 
}

1. 然后设置查询方法:

@Query("select avg(rl.rating) as rating, b as book from ReadingList rl join rl.book b group by rl.book order by rating desc")
Page<BookWithRating> findAllWithRating(Pageable pageable);

注意输出参数的别名 - 它们的名称必须与投影 getter 匹配.

Pay attention to the alias of the output parameters - their names must match the projection getters.

您也可以尝试使用 this 用于丰富数据模型的技术(请参阅如何使用 SpEL 表达式使用 @Value 注释公开的属性以公开合成属性").

Also you can try to use this technics for enriching a data model (see how to 'annotate exposed properties with @Value using SpEL expressions to expose synthetic properties').

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