@Document
public class Goods implements Serializable {

    @Id
    private String id;
    private String name;
    private String price;
    private String description;
    private String max;
    private String num;
    private String[] pictures;
    private String subMchId;

    private String tag;

    private List<Info> infos;

    public Goods(String id, String name, String price, String description, String max, String num, String[] pictures, String subMchId, String tag, List<Info> infos) {
        this.id = id;
        this.name = name;
        this.price = price;
        this.description = description;
        this.max = max;
        this.num = num;
        this.pictures = pictures;
        this.subMchId = subMchId;
        this.tag = tag;
        this.infos = infos;
    }
}

import lombok.extern.log4j.Log4j2;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.data.mongodb.core.mapreduce.GroupBy;
import org.springframework.data.mongodb.core.mapreduce.GroupByResults;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@Log4j2
@RestController
public class GoodsController {
    
    @Autowired
    private MongoTemplate mongoTemplate;
    
    @GetMapping(value = {"module"})
    public ResponseEntity<GroupByResults> module() throws Exception {
        GroupBy groupBy = new GroupBy("tag").initialDocument("{ collection: [] }").reduceFunction("function (doc,pre){pre.collection.push({id:doc._id.str,name:doc.name,pictures:doc.pictures});}");
        GroupByResults groupByResults = mongoTemplate.group("goods", groupBy, Goods.class);
        return new ResponseEntity<GroupByResults>(groupByResults, HttpStatus.OK);
    }

}

[
    {
        "id":"5cd392bbb53ac62ba8e8593f",
        "name":"蘋果",
        "price":"12.99",
        "description":"蘋果家庭的低調(diào)皇室",
        "max":"5",
        "num":"5",
        "pictures":[],
        "subMchId":"S0000001",
        "tag":"精選水果",
        "infos":null
    },
    {
        "id":"5cd393dcb53ac61810a67b8e",
        "name":"蘋果",
        "price":"12.99",
        "description":"蘋果家庭的低調(diào)皇室",
        "max":"5",
        "num":"5",
        "pictures":[],
        "subMchId":"S0000001",
        "tag":"精選水果",
        "infos":null
    },
    {
        "id":"5cd39512b53ac60b905d8602",
        "name":"蘋果",
        "price":"12.99",
        "description":"蘋果家庭的低調(diào)皇室",
        "max":"5",
        "num":"5",
        "pictures":[],
        "subMchId":"S0000001",
        "tag":"新鮮蔬菜",
        "infos":null
    }
]

{
    "rawResults":{
        "retval":[
            {
                "tag":"精選水果",
                "collection":[
                    {
                        "id":"5cd392bbb53ac62ba8e8593f",
                        "name":"蘋果",
                        "pictures":[]
                    },
                    {
                        "id":"5cd393dcb53ac61810a67b8e",
                        "name":"蘋果",
                        "pictures":[]
                    }
                ]
            },
            {
                "tag":"新鮮蔬菜",
                "collection":[
                    {
                        "id":"5cd39512b53ac60b905d8602",
                        "name":"蘋果",
                        "pictures":[]
                    }
                ]
            }
        ],
        "count":3,
        "keys":2,
        "ok":1
    },
    "count":3,
    "keys":2,
    "serverUsed":null
}