基于java程序的mongodb随机查询的一个解决方案（二）

绝地灬酷狼 2023-05-31 06:44 45阅读 0赞

在上次的   [基于java程序的mongodb随机查询的一个解决方案（一）][java_mongodb]  之后，又发现一种方法，在此记录

### mongoTemplate Aggregation ###

使用聚合查询提供的抽样方法来做随机查询，没有做性能测试。速度应该可以

package com.mongo.demo.aggregation;
    
    import com.mongo.demo.model.Person;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.data.mongodb.core.MongoTemplate;
    import org.springframework.data.mongodb.core.aggregation.Aggregation;
    import org.springframework.data.mongodb.core.aggregation.AggregationResults;
    import org.springframework.data.mongodb.core.aggregation.TypedAggregation;
    import org.springframework.stereotype.Service;
    
    import java.util.ArrayList;
    import java.util.List;
    
    /**
     * @author Tan
     * @version V1.0
     * @description: Sample  使用聚合操作随机查询
     * @date 2019/10/23
     */
    @Service
    public class Sample {
    
        @Autowired
        private MongoTemplate mongoTemplate;
    
        public List<Person> findPerson() {
    
            List<Person> personList = new ArrayList<>();
    
            // 构造随机条件，sample是聚合操作提供的随机抽样方法，此处抽样2个
            // 有两种方式 对应两个构造方法
            // 1、public static <T> TypedAggregation<T> newAggregation(Class<T> type, AggregationOperation... operations)
            Aggregation agg = Aggregation.newAggregation(Person.class, Aggregation.sample(2));
            AggregationResults<Person> peoples = mongoTemplate.aggregate(agg, Person.class, Person.class);
            peoples.forEach((person)->{
                System.out.println(peoples);
                personList.add(person);
            });
    
            //2、public static <T> TypedAggregation<T> newAggregation(Class<T> type, List<? extends AggregationOperation> operations)
            TypedAggregation<Person> aggu = Aggregation.newAggregation(Person.class, Aggregation.sample(2));
            AggregationResults<Person> aggregate = mongoTemplate.aggregate(aggu, Person.class);
            aggregate.forEach((aggr)->{
                System.out.println(aggr);
                personList.add(aggr);
            });
    
            return personList;
    
        }
    
        public void savePerson() {
            mongoTemplate.save(new Person("zhan1", "男", 23));
            mongoTemplate.save(new Person("zhan2", "男", 25));
            mongoTemplate.save(new Person("zhan3", "男", 18));
            mongoTemplate.save(new Person("zhan4", "男", 29));
            mongoTemplate.save(new Person("zhan5", "男", 56));
        }
    
    }

[java_mongodb]: https://blog.csdn.net/zhan107876/article/details/102603482