使用 mongoTemplate 在 spring-data-mongo Java 中进行 Mongo 聚合查询

Question

I am trying to convert milliseconds to dd-mm-yyyy format using spring-data-mongo APIs. Below is the required Mongo working query and corresponding Java spring code.

"$project" : {
   "serverTimestamp": 1,
   "formattedServerDate": {
       "$dateToString": {
            "format": "%d-%m-%Y",
            "date": {
                 "$toDate" : "$serverTimestamp"
            }
        }
    }
}

ProjectionOperation dateProject = Aggregation.project("serverTimestamp")
                .and(ConvertOperators.ToDate.toDate("$serverTimestamp"))
                .dateAsFormattedString("%d-%m-%Y").as("formattedServerDate");

But I am getting below error

Caused by: java.lang.IllegalStateException: Projection field name must not be null!
at org.springframework.util.Assert.state(Assert.java:73)
at org.springframework.data.mongodb.core.aggregation.ProjectionOperation$ProjectionOperationBuilder.getRequiredName(ProjectionOperation.java:1250)
at org.springframework.data.mongodb.core.aggregation.ProjectionOperation$ProjectionOperationBuilder.dateAsFormattedString(ProjectionOperation.java:1204)
at com.abcd.deda.service.EventServiceImpl.getSessionStats(EventServiceImpl.java:423)

Help!

Answer 1

Try

ProjectionOperation toDateProjectOperation = Aggregation.project("serverTimestamp")
                .andExpression("toDate(toLong(serverTimestamp))")
                    .as("formattedServerDate");

ProjectionOperation dateToStringProjectOperation = Aggregation.project("serverTimestamp")
                .and("formattedServerDate")
                .dateAsFormattedString("%d-%m-%Y")
                    .as("formattedServerDate");

newAggregation(
    ...
    toDateProjectOperation,
    dateToStringProjectOperation
    ...
)

In ProjectOperation class, dateAsFormattedString(String) calls this.operation.and(DateOperators.DateToString.dateOf(getRequiredName()).toString(format)) , but name is not defined.

The question was asked six months ago, you've probably solved it.