业务需求及设计见前文：基于 MongoDB 动态字段设计的探索

根据专业计算各科平均分 (总分、最高分、最低分)

public Object avg(String major){

    Aggregation aggregation = Aggregation.newAggregation(
            Aggregation.unwind("courseList"),
            Aggregation.match(Criteria.where("major").is(major)),
            Aggregation.group("courseList.name").avg("courseList.score").as("avg")
    ); // avg 可以替换成 sum, max, min 分别求各科总分、最高分、最低分

    AggregationResults<BasicDBObject> aggregationResults = mongoTemplate.aggregate(aggregation, Student.class, BasicDBObject.class);

    List<BasicDBObject> result = new ArrayList<>();
    for(Iterator<BasicDBObject> iterator = aggregationResults.iterator(); iterator.hasNext();){
        result.add(iterator.next());
    }

    return result;
}

计算个人总分数

public Object sum(String name){

    Aggregation aggregation = Aggregation.newAggregation(
            Aggregation.unwind("courseList"),
            Aggregation.match(Criteria.where("name").is(name)),
            Aggregation.group("name").sum("courseList.score").as("sum")
    );

    AggregationResults<BasicDBObject> aggregationResults = mongoTemplate.aggregate(aggregation, Student.class, BasicDBObject.class);

    List<BasicDBObject> result = new ArrayList<>();
    for(Iterator<BasicDBObject> iterator = aggregationResults.iterator(); iterator.hasNext();){
        result.add(iterator.next());
    }

    return result;
}

完整代码：GitHub

参考：MongoTemplate 聚合操作

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原文地址：https://www.cnblogs.com/victorbu/p/11293743.html