MongoTemplate聚合 - 按日期分组 [英] MongoTemplate aggregate - group by date

问题描述

我正在尝试使用mongotemplate创建聚合查询，其中按日期分组（即2016-03-01）而不是datetime（即2016-03-01 16:40:12）。
mongodb文档中存在 dateToString 操作，它可用于使用格式化从日期时间中提取日期：
https://docs.mongodb.org/manual/reference/operator/aggregation/dateToString/
但我得到它与mongotemplate一起工作 - 我得到一个NullPointerException。
（我的db版本是3.2）

I'm trying to create an aggregate query using mongotemplate where there's a grouping by date (i.e 2016-03-01) instead of datetime (i.e 2016-03-01 16:40:12). The dateToString operation exists in the mongodb documentation it can be used to extract the date from the datetime using formatting: https://docs.mongodb.org/manual/reference/operator/aggregation/dateToString/ but I get get it to work with mongotemplate - I get a NullPointerException. (my db version is 3.2)

List<AggregationOperation> aggregationOperations = new ArrayList<AggregationOperation>();

aggregationOperations.add(
          Aggregation.project("blabla", ...).
          andExpression("dateToString('%Y-%m-%d',timeCreated).as("date"));

aggregationOperations.add(Aggregation.group("date").sum("blabla").as("blabla"));

AggregationResults<?> aggregationResults = this.mongoTemplate.aggregate(
                        Aggregation.newAggregation(aggregationOperations),
                                    collectionName,
                                    resultClass);

当我使用 dayOfMonth（timeCreated）来提取日期时，没有例外，但是我找不到如何使用 dateToString 进行此操作的示例。我没有使用''作为日期格式，它也没有用...

When I use dayOfMonth(timeCreated) to extract the day, there's no exception, but I couldn't find and example of how to make this work with dateToString. I tried without '' for the date format, and it also didn't work...

这是我得到的例外：

java.lang.NullPointerException
    at org.bson.BasicBSONEncoder._putObjectField(BasicBSONEncoder.java:226)
    at org.bson.BasicBSONEncoder.putObject(BasicBSONEncoder.java:194)
    at org.bson.BasicBSONEncoder._putObjectField(BasicBSONEncoder.java:255)
    at org.bson.BasicBSONEncoder.putObject(BasicBSONEncoder.java:194)
    at org.bson.BasicBSONEncoder._putObjectField(BasicBSONEncoder.java:255)
    at org.bson.BasicBSONEncoder.putObject(BasicBSONEncoder.java:194)
    at org.bson.BasicBSONEncoder._putObjectField(BasicBSONEncoder.java:255)
    at org.bson.BasicBSONEncoder.putIterable(BasicBSONEncoder.java:324)
    at org.bson.BasicBSONEncoder._putObjectField(BasicBSONEncoder.java:263)
    at org.bson.BasicBSONEncoder.putObject(BasicBSONEncoder.java:194)
    at org.bson.BasicBSONEncoder.putObject(BasicBSONEncoder.java:136)
    at com.mongodb.DefaultDBEncoder.writeObject(DefaultDBEncoder.java:36)
    at com.mongodb.OutMessage.putObject(OutMessage.java:289)
    at com.mongodb.OutMessage.writeQuery(OutMessage.java:211)
    at com.mongodb.OutMessage.query(OutMessage.java:86)
    at com.mongodb.DBCollectionImpl.find(DBCollectionImpl.java:81)
    at com.mongodb.DB.command(DB.java:320)
    at com.mongodb.DB.command(DB.java:299)
    at com.mongodb.DB.command(DB.java:374)
    at com.mongodb.DB.command(DB.java:246)
    at org.springframework.data.mongodb.core.MongoTemplate$2.doInDB(MongoTemplate.java:357)
    at org.springframework.data.mongodb.core.MongoTemplate$2.doInDB(MongoTemplate.java:355)
    at org.springframework.data.mongodb.core.MongoTemplate.execute(MongoTemplate.java:442)
    at org.springframework.data.mongodb.core.MongoTemplate.executeCommand(MongoTemplate.java:355)
    at org.springframework.data.mongodb.core.MongoTemplate.aggregate(MongoTemplate.java:1497)
    at org.springframework.data.mongodb.core.MongoTemplate.aggregate(MongoTemplate.java:1432)

编辑：

最终我们在这里决定采用与下面建议不同的解决方案，我在这里写，以防其他人认为它有用：

Eventually we decided here on a different solution than what was suggested below, I'm writing it here in case anyone else finds it useful:

除了保存日期时间的timeCreated字段，我们在文档中保存了另一个字段：date，它只保存日期（长）。

In addition to the "timeCreated" field which holds the datetime, we saved another field in the document: "date", that holds just the date (as long).

例如，如果 timeCreated=2015-12-24 16：36：06.657 + 02:00，然后日期是2015-12-24 00:00:00，我们节省了1449180000000.
现在我们可以简单地分组通过date。

For example if "timeCreated" = "2015-12-24 16:36:06.657+02:00", then date is "2015-12-24 00:00:00", and we save 1449180000000. Now we can simply group by "date".

推荐答案

您可以尝试使用 SpEL andExpression 在投影操作中，然后按群组操作中的新字段分组：

You could try projecting the fields first by using the SpEL andExpression in the projection operation and then group by the new fields in the group operation:

Aggregation agg = newAggregation(
    project()       
        .andExpression("year(timeCreated)").as("year")
        .andExpression("month(timeCreated)").as("month")
        .andExpression("dayOfMonth(timeCreated)").as("day"),
    group(fields().and("year").and("month").and("day"))     
        .sum("blabla").as("blabla")
);

AggregationResults<BlaBlaModel> result = 
    mongoTemplate.aggregate(agg, collectionName, BlaBlaModel.class);
List<BlaBlaModel> resultList = result.getMappedResults();

这篇关于MongoTemplate聚合 - 按日期分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IT屋！