如何使用Spring数据从Mongo中的数组文档字段中仅获取匹配结果 [英] How to Get Only Matched Result from An Array Field of Document in Mongo Using Spring Data
问题描述
我正在使用 spring boot 1.5.1 和 MongoDB版本3.4.6 。
我有一个mongo文件酒店，里面有一份评论清单。
I have a mongo document Hotel which has a list of Review .
评论 class有属性 userName 。
The Review class has property userName.
@Document
public class Hotel {
@Id
private String id;
private List<Review> reviews;
我想通过评论userName搜索所有酒店。
I want to search all the hotel by Review userName.
我的 HotelRepository 有公开列表< Hotel> findByReviewsUserName（String userName）;
当我与用户'Salman'打电话时 -
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
}
]
}
]
我想要的是什么只评论'Salman'，但它也会返回给其他人。
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？
我注意到的是，如果单个评论用户匹配，则会返回我不想要的评论列表，我希望我按名称搜索评论。
推荐答案
命名查询的工作原理应该如此。您并未明确表示只需要文档的一部分，因此查询将返回整个文档。要实现，您不能使用命名查询 （请参阅@alexefimov使用 @Query 注释帮助使用命名查询的答案）但您可以在 MongoRepository 旁边使用 MongoTemplate 。要做到这一点你必须做出一些改变：
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:
首先你的存储库应该是这样的：
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);
}
用于实现 MongoTemplateRepository 方法，你会写一个新类。 重要的事情是，您应该将此类命名为您的存储库类名+ Impl 。否则，spring-data无法找到您的方法实现 MongoTemplateRepository 中定义的方法。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那样我们可以 .include（）或 .exclude 查询字段。虽然您想要包含数组字段的匹配部分，但我们使用 $ 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：您仍然可以使用弹性数据支持良好的命名查询，此外，如果您需要聚合或子文档的某些复杂查询，则无法通过spring构建命名查询，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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