java – Spring Data MongoDb是否支持$filter数组聚合运算符？

我正在尝试使用MongoTemplate在Spring Data中实现以下工作mongoDb查询：

db.answers.aggregate([
        { "$match" : { "object_id" : "1" } },
        { "$project": { 'answer_list': 1, 'profile': { $filter : { input: '$answer_list', as: 'answer', cond: { $eq: [ '$$answer.question', 2 ] } } } } },
        { "$unwind" : "$profile"},
        { "$unwind" : "$answer_list"},
        { "$group" : { "_id" : { "question" : "$answer_list.question", "answer" : "$answer_list.answer", "criteria" : "$profile.answer"}, "count" : { "$sum" : 1 } } },
        { "$sort" : { "_id.question" : 1, "_id.answer" : 1 } }
]);

该集合具有以下结构：

{
"_id" : ObjectId("..."),
"object_id" : ObjectId("..."),
"answer_list" : [ 
    {
        "question" : NumberLong(0),
        "answer" : NumberLong(0)
    }, 
    {
        "question" : NumberLong(1),
        "answer" : NumberLong(2)
    }, 
    {
        "question" : NumberLong(2),
        "answer" : NumberLong(2)
    }
]}

我在这里要做的是关于简单调查提交数据的报告.问题是“对第一个问题回答0的用户如何回答第二个问题？”
我花了一整天时间搜索SpringData Mongo Db文档,但我什么也没找到.
有人可以帮忙吗？

TIA

解决方法:

您可以通过提供自己的AggregationExpression来解决此问题.

ProjectionOperation agg = Aggregation.project() //

      .and(new AggregationExpression() {

        @Override
        public DBObject toDbObject(AggregationOperationContext context) {

          DBObject filterExpression = new BasicDBObject();
          filterExpression.put("input", "$answer_list");
          filterExpression.put("as", "answer");
          filterExpression.put("cond", new BasicDBObject("$eq2", Arrays.<Object> asList("$$answer.question", 2)));

          return new BasicDBObject("$filter", filterExpression);
        }
      }).as("profile");

标签：java,spring,mongodb,spring-data-mongodb
来源： https://codeday.me/bug/20191003/1849647.html