Spring Data Mongodb:QueryDsl Predicate 和 Criteria API 互操作性 [英] Spring data Mongodb: QueryDsl Predicate and Criteria API interoperability

问题描述

我在 Spring Data Mongodb 中使用 QueryDSL 谓词.但是，我面临着必须将 Query API 与 MongoTemplate 一起使用的情况(例如，过滤要从 Mongo 获取的字段).这是一个简单的例子:

I'm using QueryDSL predicates with Spring Data Mongodb. However, I'm facing situations where I have to use the Query API with MongoTemplate (for instance to filter fields to fetch from Mongo). Here is a simple example:

public Stream<MyModel> findSummary(Predicate predicate){
    Query query = new Query();
    query.fields.include("field1").include("field2");
    return mongoTemplate.stream(query, MyModel.class);
}

我想将谓词转换为标准，以便我可以执行以下操作:

I would like to transform my Predicate into a Criteria so that I could do something like:

Query query = new Query();
query.addCriteria(XXXXX.toCriteria(predicate));

但是我找不到这样的实用程序类.

However I cannot find such utility class.

我发现可以访问 QueryDSL 谓词，因此我开始实现自定义访问者 (com.mysema.query.types.Visitor)，但 Criteria API 并非为此目的而设计:例如实现简单的"and" QueryDSL (com.mysema.query.types.Ops#AND) 的操作符必须变成类似

I've found that a QueryDSL Predicate can be visited and so I started implementing a custom Visitor (com.mysema.query.types.Visitor) but the Criteria API was not designed for this purpose: for example implementing the simple "and" operator of QueryDSL (com.mysema.query.types.Ops#AND) has to be turned into something like

<result of left argument visit assumed to be a Criteria>.and("<path of right argument>").<operator of right argument>(<result of right argument visit>);

有人可以建议一种使 QueryDSL Predicates 和 Spring Data Mongodb Query 互操作的方法吗?

Can someone suggest an approach to make QueryDSL Predicates and Spring Data Mongodb Query interoperate ?

谢谢

贝努瓦

推荐答案

我遇到了同样的问题，但在 Internet 上没有找到针对此问题的任何解决方案.经过多次试验&错误，我已经实施了一个在我的项目中运行良好的自定义解决方案，它可能会帮助其他人.

I ran into same problem and did not find any solution on internet for this problem. After many trial & errors, I have implemented a custom solution that works well in my project and it may help others.

注意

使用的版本:

• spring-data-mongodb - 3.0.2.RELEASE
• querydsl - 4.3.1

实现

首先创建一个扩展的类 org.springframework.data.mongodb.repository.support.SpringDataMongodbQuery &使用 public 修饰符覆盖 createQuery(Predicate predicate) 方法.

first create a class that extends org.springframework.data.mongodb.repository.support.SpringDataMongodbQuery & override createQuery(Predicate predicate) method with public modifier.

public class CustomSpringDataMongodbQuery<T> extends SpringDataMongodbQuery<T> {

    public CustomSpringDataMongodbQuery(MongoOperations operations, Class<? extends T> type) {
        super(operations, type);
    }

    @Override
    public Document createQuery(Predicate predicate) {
        return super.createQuery(predicate);
    }
}

现在创建一个实现org.springframework.data.mongodb.core.query.CriteriaDefinition的类.

public class DocumentCriteria implements CriteriaDefinition {

    private final Document criteriaObject;

    public DocumentCriteria(Document criteriaObject) {
        this.criteriaObject = criteriaObject;
    }

    @Override
    public Document getCriteriaObject() {
        return criteriaObject;
    }

    @Override
    public String getKey() {
        return null;
    }
}

现在您可以使用这两个类从谓词中获取查询.

now you can obtain query from predicate using these two classes.

Document document = new CustomSpringDataMongodbQuery<>(mongoTemplate, MyModel.class).createQuery(predicate);
Query query = Query.query(new DocumentCriteria(document));

投影查询

如果你想使用QClass字段进行投影，那也是可以的.

If you want to use QClass fields for projection, then it's also possible.

在 CustomSpringDataMongodbQuery 类中，添加方法

In CustomSpringDataMongodbQuery class, add method

public Query createQuery(Predicate filter, List<Path<?>> fields) {
    QTuple qTuple = Projections.tuple(fields.toArray(new Path[0]));
    return createQuery(filter, qTuple, QueryModifiers.EMPTY, Collections.emptyList());
}

并传递路径列表(QClass 字段)以及谓词

and pass list of Path(QClass fields) along with predicate

使用投影和查询进行查询分页

您可以使用

public Query createQuery(Predicate filter, List<Path<?>> fields, int page, int size, List<OrderSpecifier<?>> orderSpecifiers) {
    QTuple qTuple = Projections.tuple(fields.toArray(new Path[0]));
    QueryModifiers queryModifiers = new QueryModifiers((long) size, (long) (page - 1) * size);
    return createQuery(filter, qTuple, queryModifiers, orderSpecifiers);
}

希望这对所有想要使 QueryDSL Predicates 和 Spring Data Mongodb Query 互操作的人有所帮助.

Hope this helps everyone who wants to make QueryDSL Predicates and Spring Data Mongodb Query interoperate.

欢迎提出任何建议！！

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