MongoRepository 动态查询 [英] MongoRepository dynamic queries

问题描述

我有以下问题.假设我有以下模型对象:

I have the following problem. Lets say I have the following model object:

class Person {
    String id;
    String firstName;
    String lastName;
    Map<String, String> properties;
}

在属性图中，您可以插入任何类型的属性，没有限制.

In the properties map, you can insert any kind of property, there are no constrains.

上述对象保存在一个 MongoDB 中，如下所示:

The above object is saved in a MongoDB which looks like this:

public interface PersonRepo extends MongoRepository<Person, String> {
}

当一个人被保存到存储库中时，Mapproperties 变平了.例如，如果我们有以下对象:

When a person is saved into the repository the Map<String, String> properties is flatten up. As an example, if we have the following object:

Person: {
    id := 1;
    firstName := John,
    lastName  := Doe,
    properties := {
        age: 42
    }
}

保存在 MongoRepository 中的文档如下:

the document saved in the MongoRepository will be the following:

Person: {
    id := 1;
    firstName := John,
    lastName  := Doe,
    age := 42
}

现在我的问题是我必须根据(例如)寻找对象，如果它们具有特定的属性.假设我想要定义了年龄属性的所有人员.一个重要的附加要求是我应该返回一个分页结果.

Now my problem is that I have to look for objects based on (for example), if they have a specific property or not. Lets say I want all Persons for which an age property has been defined. One important additional requirement is that I should return a paged result.

我试过使用

findAll(Example<Person> example, Pageable pageable)

但是由于某种原因这不起作用.我怀疑这是因为我的模型对象和 MongoDB 文档具有不同的结构.

But this does not work for some reason. I suspect that it's the fact that my model object and the MongoDB Document have different structures.

我也尝试过使用 QueryDsl(这里有一个例子:http://www.baeldung.com/queries-in-spring-data-mongodb)但也没有成功，而且对我来说这个解决方案也不是很优雅(必须维护生成的类等.另外我有一种感觉，因为我的 Map properties 对象成员，它不会工作.

I've also tried with the QueryDsl (here you have an example: http://www.baeldung.com/queries-in-spring-data-mongodb) but with no success either, and also to me this solution is not to elegant (having to mantain generated classes and alike. Also I have a feeling it will not work because of my Map<String, String> properties object member).

我想到的另一个足够优雅的解决方案是具有以下功能:

Another solution that came to my mind and would be elegant enough, is to have the following function:

@Query(value = "?0")
Page<Query> findByQuery(String query, Pageable pageable)

在这种情况下，我将能够手动构建查询，而不必对运行搜索所用的键进行硬编码.我现在的问题是，如何将查询值设置为我的第一个参数?使用上面显示的示例，我收到以下错误

In this case I would be able to manually construct the query and I wouldn't have to hardcode the key by which I run the search. My question now is, how can set the query value to be exactly my first parameter? With the example showned above I get the following error

java.lang.ClassCastException: java.lang.String cannot be cast to com.mongodb.DBObject

另一种解决方案是使用 mongoTemplate 并在给定一些 Criteria 的情况下进行查询，如下例所示:

One other solution would be to use mongoTemplate and query given some Criteria as in the following example:

    final Query query = new Query();
    query.addCriteria(Criteria.where("age").regex(".*"));

    mongoTemplate. find(query, Person.class);

这个解决方案的问题在于它返回一个对象列表而不是分页结果.如果我添加 query.with(new PageRequest(3, 2)); ，它也会返回一个特定的页面，但在这种情况下，我无法手动构建分页"结果，因为我不知道总数元素数量.

The problem with this solution is that it returns a list of objects instead for a paged result. It cal also return a specific page if I add query.with(new PageRequest(3, 2)); but in this case I cannot manually construct the "paged" result because I do not know the total number of elements.

你还有什么其他想法可以帮助我吗?

Do you have any other ideas that could help me?

提前致谢！

推荐答案

Bellow 是我想出的解决方案.所以简单回顾一下，我遇到的问题是，我无法在给定 Query 对象作为输入的情况下执行查询，以提高过滤条件的灵活性.结果证明解决方案很简单，我只需要仔细阅读文档:)

Bellow is the solution I've come up with. So just to recap, the problem that I had, was that I wan't able to execute a query given an Query object as input to have increased flexibility over the filtering criterias. The solution turned out to be quite simple, I just had to carefully read the documentation :).

1. 步骤

扩展 MongoRepository 并添加您的自定义函数:

Extends MongoRepository and add your custom functions:

@NoRepositoryBean
public interface ResourceRepository<T, I extends Serializable> extends MongoRepository<T, I> {

    Page<T> findAll(Query query, Pageable pageable);
}

1. 步骤

为此接口创建一个实现:

Create an implementation for this interface:

public class ResourceRepositoryImpl<T, I extends Serializable> extends SimpleMongoRepository<T, I> implements ResourceRepository<T, I> {

    private MongoOperations mongoOperations;
    private MongoEntityInformation entityInformation;

    public ResourceRepositoryImpl(final MongoEntityInformation entityInformation, final MongoOperations mongoOperations) {
        super(entityInformation, mongoOperations);

        this.entityInformation = entityInformation;
        this.mongoOperations = mongoOperations;
    }

    @Override
    public Page<T> findAll(final Query query, final Pageable pageable) {
        Assert.notNull(query, "Query must not be null!");

        return new PageImpl<T>(
                mongoOperations.find(query.with(pageable), entityInformation.getJavaType(), entityInformation.getCollectionName()),
                pageable,
                mongoOperations.count(query, entityInformation.getJavaType(), entityInformation.getCollectionName())
        );
    }
}

1. 步骤

将您的实现设置为默认的 MongoRepository 实现:

Set your implementation as the default MongoRepository implementation:

@EnableMongoRepositories(repositoryBaseClass = ResourceRepositoryImpl.class)
public class MySpringApplication {
    public static void main(final String[] args) {
        SpringApplication.run(MySpringApplication.class, args);
    }
}

1. 步骤

为您的自定义对象创建一个存储库:

Create a repository for your custom object:

public interface CustomObjectRepo extends ResourceRepository<CustomObject, String> {
}

现在，如果您有多个对象想要保存在 mongo 文档存储中，那么定义一个扩展您的 ResourceRepository 的接口就足够了(如步骤 4 中所示)，您将拥有可用 Page;findAll(Query query, Pageable pageable) 自定义查询方法.我发现这个解决方案是我尝试过的最优雅的解决方案.

Now if you have multiple objects which you want to save in a mongo document store, it is enough to define an interface which extends your ResourceRepository (as seen in step 4), and you will have available the Page<T> findAll(Query query, Pageable pageable) custom query method. I have found this solution to be the most elegant of the solution I've tried.

如果您有任何改进建议，请与社区分享.

If you have any suggestions for improvements, please share them with the community.

问候，克里斯蒂安

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