如何使用 Spring Data 从 Mongo 中的文档数组字段中仅获取匹配的结果

问题描述

我正在使用 spring boot 1.5.1 和 MongoDB 3.4.6 版.

我有一个 mongo 文档 Hotel ，其中包含 Review 列表.

I have a mongo document Hotel which has a list of Review .

Review 类具有属性userName.

@Document
public class Hotel {

    @Id
    private String id;
    private List<Review> reviews;

我想通过 Review userName 搜索所有酒店.

I want to search all the hotel by Review userName.

我的 HotelRepository 有 public ListfindByReviewsUserName(String userName);

当我与用户Salman"通话时 -

When I am calling with user 'Salman' -

List<Hotel> list = this.hotelRepository.findByReviewsUserName(user);

此方法返回如下结果:

[
    {
        "id": "59b23c39c70ff63135f76b14",
        "name": "Signature",
        "reviews": [
            {
                "id": 1,
                "userName": "Salman",
                "rating": 8,
                "approved": true
            },
            {
                "id": 2,
                "userName": "Shahrukh",
                "rating": 5,
                "approved": false
            }
        ]
    }
]

我只想要Salman"的评论，但它也为其他人返回.

What I want the reviews only of 'Salman' but it's also returning for others also.

我缺少什么或怎么做?

我注意到，如果单个评论用户匹配它会返回我不想要的评论的整个列表，我想要按名称搜索的评论.

推荐答案

命名查询按原样工作.您并没有明确说您只想要文档的一部分，因此查询返回整个文档.要实现这一点您不能使用命名查询 (请参阅@alexefimov 答案，了解在 @Query 注释的帮助下使用命名查询)，但您可以使用 <MongoRepository 旁边的代码>MongoTemplate.为此，您必须进行一些更改:

The named query works as it should be. You are not explicitly saying that you want only a portion of document so query returns whole document. To achieve that you cannot use named queries (see @alexefimov answer for using named queries with help of @Query annotation) but you can use MongoTemplatebeside of MongoRepository. to do that you have to make some changes:

首先你的仓库应该是这样的:

First your repository should be like this:

public interface HotelRepository extends MongoRepository<Hotel, String>, MongoTemplateRepository {
    // You can continue to write your named queries here. Spring will create that.
}

MongoTemplateRepository:

MongoTemplateRepository:

public interface MongoTemplateRepository {
    // You will write your queries which will use mongoTemplate here. 
    List<Hotel> findByReviewsUserName(String userName);
}

为了实现 MongoTemplateRepository 方法，您将编写一个新类.重要的是你应该将这个类命名为你的存储库类名+Impl.否则 spring-data 无法找到 MongoTemplateRepository 中定义的方法实现的位置.所以你的实现类的名字应该是 HotelRepositoryImpl

For implementation of MongoTemplateRepository methods, you will write a new class. The important thing here is that you should named this class your repository class name + Impl. Otherwise spring-data cannot find where your methods implementation those defined in MongoTemplateRepository. So your implementation class's name should be HotelRepositoryImpl

public class HotelRepositoryImpl implements MongoTemplateRepository {

    @Autowired
    private MongoTemplate mongoTemplate; // we will use this to query mongoDb

    @Override
    public List<Hotel> findByReviewsUserName(String userName) {
        Query query = new Query();
        query.addCriteria(Criteria.where("reviews.username").is(userName));
        query.fields().include("reviews.$");
        return mongoTemplate.find(query, Hotel.class);
    }
}

用法:

hotelRepository.findByReviewsUserName("userName");

正如您在代码中看到的，我们可以为查询添加 .include() 或 .exclude 字段.当您想包含数组字段的匹配部分时，我们使用 $ 运算符和数组字段名称.

As you can see in codes we can .include() or .excludefields for the query. While you want to include just matched part of an array field, we use $operator with array field name.

结论:您仍然可以使用 spring-data 支持良好的命名查询，此外，如果您需要 聚合 或对无法构建命名查询的子文档进行一些复杂查询到春天，您可以在新创建的 mongoTemplate 存储库类中执行此操作.您可以从 HotelRepository 访问所有存储库方法.

Conclusion: You can still use spring-data well supported named queries and additionally if you need aggregation or some complex queries for sub documents that a named query cannot be built by spring, you can do it in your newly created mongoTemplate repository class. And you can access all of your repository methods from HotelRepository.

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