使用 spring mongotemplate 的条件查询

Question

我想使用条件查询。

这是我的查询

db.projects.aggregate([
{
    "$group": {
        "_id": "$iecode",
        "treatmentArms": { "$first": "$evaluationDTOList" }
    }
},
{ "$unwind": "$treatmentArms" },
{
    "$group": {
        "_id": null,
        "Package": { 
            "$sum": { 
               "$cond": [ 
                   { "$eq": [ "$treatmentArms.mechanismOrPkg", "Package" ] }, 
                   1, 0
                ] 
            }
        },
        "Constraint-relaxing mechanisms": { 
            "$sum": { 
               "$cond": [ 
                    { 
                        "$and": [
                            { "$eq": [ "$treatmentArms.mechanismOrPkg", "Mechanism" ] },
                            { "$eq": [ "$treatmentArms.mechanismTested1", "Constraint-relaxing mechanisms" ] }
                        ]
                    }, 
                    1, 
                    0 ]
            }
        },
        "Delivery mechanisms": { 
            "$sum": { 
               "$cond": [ 
                    { 
                        "$and": [
                            { "$eq": [ "$treatmentArms.mechanismOrPkg", "Mechanism" ] },
                            { "$eq": [ "$treatmentArms.mechanismTested1", "Delivery mechanisms" ] }
                        ]
                    }, 
                    1, 
                    0 ]
            }
        },
        "Other": { 
            "$sum": { 
               "$cond": [ 
                    { 
                        "$and": [
                            { "$eq": [ "$treatmentArms.mechanismOrPkg", "Mechanism" ] },
                            { "$eq": [ "$treatmentArms.mechanismTested1", "Other" ] }
                        ]
                    }, 
                    1, 
                    0 ]
            }
        }
    }
}
])

这是我的java代码

DBObject groupByIECode = new BasicDBObject("$group",
                new BasicDBObject("_id", new BasicDBObject("iecode","$iecode")).append("treatmentArms",new BasicDBObject("$first","$evaluationDTOList")));
        System.out.println("groupByIECode: "+groupByIECode.toString());

        DBObject unwind = new BasicDBObject("$unwind","$treatmentArms");
        System.out.println("unwind: "+unwind.toString());


        DBObject finalCalculation = new BasicDBObject("$group",new BasicDBObject("_id",null))
                                    .append(
                                            "Package", new BasicDBObject(
                                                "$sum", new BasicDBObject(
                                                    "$cond", new Object[]{
                                                        new BasicDBObject(
                                                            "$eq", new Object[]{ "$treatmentArms.mechanismOrPkg", "Package"}
                                                        ),
                                                        1,
                                                        0
                                                    }
                                                )
                                            )
                                        );

        System.out.println("finalCalculation: "+finalCalculation);
        final AggregationOutput output = projects.aggregate(match,groupByIECode,unwind,finalCalculation);

它给了我MongoException$DuplicateKey

后来发现spring mongotemplate不支持$cond运算符。那么我该如何使用 spring mongotemplate.

来实现这个条件查询呢？

This link 有一些解释，但没有显示完整的实现

Answer 1

来自 documentation，使用 Spring 数据 MongoDB 支持 MongoDB 聚合框架的规范示例如下所示：

import static org.springframework.data.mongodb.core.aggregation.Aggregation.*;

Aggregation agg = newAggregation(
    pipelineOP1(),
    pipelineOP2(),
    pipelineOPn()
);

AggregationResults<OutputType> results = mongoTemplate.aggregate(agg,
    "INPUT_COLLECTION_NAME", OutputType.class);
List<OutputType> mappedResult = results.getMappedResults();

Note that if you provide an input class as the first parameter to the newAggregation method the MongoTemplate will derive the name of the input collection from this class. Otherwise if you don’t specify an input class you must provide the name of the input collection explicitly. If an input-class and an input-collection is provided the latter takes precedence.

对于您的查询，创建一个实现 AggregationOperation 接口的变通方法，以接收表示聚合管道中单个组操作的 DBObject使用 $cond 运算符：

public class GroupAggregationOperation implements AggregationOperation {
    private DBObject operation;

    public GroupAggregationOperation (DBObject operation) {
        this.operation = operation;
    }

    @Override
    public DBObject toDBObject(AggregationOperationContext context) {
        return context.getMappedObject(operation);
    }
}

然后将 $group 操作作为聚合管道中的 DBObject 实现，与您拥有的相同：

DBObject operation = (DBObject) new BasicDBObject("$group", new BasicDBObject("_id", null))
    .append(
        "Package", new BasicDBObject(
            "$sum", new BasicDBObject(
                "$cond", new Object[]{
                    new BasicDBObject(
                        "$eq", new Object[]{ "$treatmentArms.mechanismOrPkg", "Package"}
                    ),
                    1,
                    0
                }
            )
        )
    );

然后您可以将其用作：

import static org.springframework.data.mongodb.core.aggregation.Aggregation.*;

GroupAggregationOperation groupOp = new GroupAggregationOperation(operation);
Aggregation agg = newAggregation(
    group("iecode").first("treatmentArms").as("treatmentArms"),
    unwind("treatmentArms"),
    groupOp 
);
AggregationResults<Entity> results = mongoTemplate.aggregate(agg, Entity.class); 
List<Entity> entities = results.getMappedResults();

使用 spring mongotemplate 的条件查询

Conditional query with spring mongotemplate

spring

mongodb

aggregation-framework

spring-mongodb