Spring Data Mongo - 如何通过@DBRef字段的id进行查询 [英] Spring Data Mongo - How to query by @DBRef field's id

问题描述

我是Spring Data Mongo的新手，所以我必须做错事，因为我无法设法执行这么简单的查询。这是我的模特：

I am new to Spring Data Mongo so I must be doing something wrong because I can't manage to execute such a simple query. This is my model:

@Document(collection="brands")
public class Brand{
    @Id
    private int id;

    private String name;
    ...
    //getters-setters
}

@Document(collection="models")
public class Model{
    @Id
    private int id;
    private String name;
    @DBRef
    private Brand brand;
    ...
    //getters-setters
}

我想从一个品牌获得所有模型，所以我按如下方式实现DAO：

I would like to get all models from a brand, so I implement the DAO as follows:

@Repository
public interface IModelDAO extends MongoRepository<Model, Integer>{
    @Query(value="{ 'brand.$id' : ?0 }")
    public List<Model> findByBrandId(Integer id);   
}

如果我在shell中执行这个mongodb查询它可以工作： db.modelss.find（{'brand。$ id'：1}）

If I execute this mongodb query in the shell it works: db.modelss.find({ 'brand.$id' : 1 })

但是，Java应用程序抛出以下异常：

But, the Java application throws the following exception:

Caused by: java.lang.IllegalAccessError
at org.springframework.data.mapping.PropertyReferenceException.detectPotentialMatches(PropertyReferenceException.java:134)

显然它正在寻找Brand类中的字段$ id，因为它不存在它失败了。所以我将查询更改为以下内容，以便导航到id字段：

Apparently it is looking for a field $id in Brand class, and since it doesn't exist it fails. So I change the query to the following, so that it navigates to the id field:

@Query(value="{ 'brand.id' : ?0 }")

现在，它不会抛出异常，但它在DB中找不到任何内容。

Now, it doesn't throw an exception but it doesn't find anything in the DB.

调试MongoTemplate.executeFindMultiInternal（）方法可以看到

Debugging the MongoTemplate.executeFindMultiInternal() method in can see that in

DBCursor cursor = null;
    try {
        cursor = collectionCallback.doInCollection(getAndPrepareCollection(getDb(), collectionName));

光标的查询是 query = {brand：134} 。所以它没有找到任何东西是有道理的。在调试期间将查询值更改为query = {brand。$ id：134}它可以正常工作。

cursor's query is query={ "brand" : 134}. So it makes sense it doesn't find anything. Changing the query value during debugging to query={ "brand.$id" : 134} it works.

那么，为什么查询没有正确翻译？

So, why isn't the query correctly translated?

推荐答案

问题是由 @Id int 类型。将其更改为整数解决了它：

The problem was caused by the @Id int type. Changing it to Integer solved it:

@Document(collection="brands")
public class Brand{
    @Id
    private Integer id;

    private String name;
    ...
    //getters-setters
}

@Document(collection="models")
public class Model{
    @Id
    private Integer id;
    private String name;
    @DBRef
    private Brand brand;
    ...
    //getters-setters
}

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