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spring data mongodb中投影中int数组字段求和的方法

spring-mongodb spring-data-mongodb aggregation-framework spring-data mongodb

4

Adarsh Patel · 技术社区 · 7 年前

收集的样本文件

{
    "_id" : 2,
    "student" : "Ryan",
    "homework" : [
        5,
        6,
        5
    ],
    "quiz" : [
        8,
        8
    ],
    "extraCredit" : 8
}

mongodb中的聚合查询

db.scores.aggregate([
     {
        $project : {
            _id:"$_id",
            hSum : { $sum: "$homework" },
            qSum : { $sum: "$quiz"},
        }
     }])

上述聚合查询的输出

{
    "_id" : 2,
    "hSum" : 16,
    "qSum" : 16
}

我想将上面的mongo查询转换为spring数据格式。我想在spring数据中使用projectionOperations进行聚合。如何使用projectionOperation编写?

1 回复 | 直到 7 年前

1

4

pvpkiran 7 年前

这应该行得通

MatchOperation matchOperation = match(Criteria.where("_id").is(2));

AggregationExpression homeworkExpression = AccumulatorOperators.Sum.sumOf("homework");
AggregationExpression quizExpression = AccumulatorOperators.Sum.sumOf("quiz");
ProjectionOperation projectionOperation = project("someId").and(homeworkExpression).as("hSum")
        .and(quizExpression).as("qSum");

Aggregation aggregation = newAggregation( matchOperation, projectionOperation);
AggregationResults<Result> results = mongoTemplate.aggregate(aggregation, "ScoresColletionName", Result.class);

您可以像这样创建一个名为Result的类来获取值

@Getter
@Setter
class Result {
    private int someId;
    private int hSum;
    private int qSum;
}