问题描述

我正在尝试从 Spring Framework 项目的 MongoDB 中的数组中获取元素.

I am trying to fetch an element from an array in the MongoDB in my Spring Framework project.

我找到了MongoDB shell的解决方案，但我不知道如何通过Spring.data.core.aggregation实现它，Spring不支持聚合运算符@addFields之一.

I have find the solution for MongoDB shell, but I do not know how to implement it by Spring.data.core.aggregation, one of aggregation operator @addFields is not supported by Spring.

谁能告诉我如何替换这个@addField 或如何以另一种方式实现它?非常感谢！！！

Could anyone tell me how to replace this @addField or how to implement in it another way? Thank you so much!!!

MongoDB 示例数据:

MongoDB sample data:

{
    "_id" : 15,
    "items" : [
            {
                    "columns" : [
                            {
                                    "title" : "hhh",
                                    "value" : 10
                            },
                            {
                                    "title" : "hahaha",
                                    "value" : 20
                            }
                    ]
            },
            {
                    "columns" : [
                            {
                                    "title" : "hiii",
                                    "value" : 50
                            }
                    ]
            }
    ]
}

预期结果:

{
"_id" : 15,
"items" : [
        {
                "columns" : [
                        {
                                "title" : "hahaha",
                                "value" : 20
                        }
                ]
        },
        {
                "columns" : []
        }
]

}

MongoDB Shell的解决方案:

The solution for MongoDB Shell:

let value = "hahaha";

db.coll.aggregate([
    {
        "$addFields": { 
            "items": { 
                "$map": { 
                    "input": "$items", 
                    "as": "item", 
                    "in": { 
                        "columns": { 
                            "$filter": { 
                                "input": "$$item.columns", 
                                "as": "elt", 
                                "cond": { "$eq": [ "$$elt.title", value ] } 
                            } 
                        }
                    }
                } 
            } 
        } 
    } 
])

MongoDB 版本:3.4.1
春季版:1.4.3

MongoDB version: 3.4.1
Spring version: 1.4.3

推荐答案

您可以尝试以下方法，但您需要使用 1.8.5 版本.

You can try the following but you'll need to use 1.8.5 version.

Aggregation aggregation = newAggregation(
            project("_id").and(new AggregationExpression() {
                @Override
                public DBObject toDbObject(AggregationOperationContext aggregationOperationContext) {
                    DBObject filter = new BasicDBObject("input", "$$item.columns").append("as", "elt").append("cond",
                            new BasicDBObject("$eq", Arrays.<Object>asList("$$elt.title", "hahaha")));
                    DBObject map = new BasicDBObject("input", "$items").append("as", "item").append("in", filter);
                    return new BasicDBObject("$map", map);
                }
            }).as("items")
  );

在 1.10.0.RC1 中添加了对一些 Mongo3.2 聚合运算符的支持.如果您可以更新到发布候选版本，您可以使用以下版本.我在 RC 中找不到 $addFields 阶段，所以保留了 $project 阶段.

The support for some of Mongo3.2 aggregation operators were added in 1.10.0.RC1. If you are okay with updating to release candidate version you can use the below version. I couldn't find $addFields stage in the RC so kept the $project stage.

Aggregation aggregation = newAggregation(
            project("_id")
                    .and(mapItemsOf("items").as("item").andApply(filter("item.columns")
                            .as("elt")
                            .by(valueOf("elt.title").equalToValue("hahaha"))
                    )).as("items")
);

静态导入:

import static org.springframework.data.mongodb.core.aggregation.Aggregation.*;
import static org.springframework.data.mongodb.core.aggregation.ArrayOperators.Filter.filter;
import static org.springframework.data.mongodb.core.aggregation.ComparisonOperators.Eq.valueOf;
import static org.springframework.data.mongodb.core.aggregation.VariableOperators.mapItemsOf;

这篇关于Spring框架中子文档数组字段中的过滤数组的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持跟版网！