java - How to do a Mongo aggregation query in Spring Data?

Question

It's the first time I am using Mongo in Java and I am having some problems with this aggregation query. I can do some simple queries in Mongo for Spring with @Query annotation in my Repository interface which extends the MongoRepository<T, ID>. It would be helpful to know which approach to take when you do long aggregations in Spring-Data.

db.post.aggregate([
    {
      $match: {}
    },
    {
      $lookup: {
        from: "users",
        localField: "postedBy",
        foreignField: "_id",
        as: "user"
      }
    },
    {
      $group: {
        _id: {
          username: "$user.name",
          title: "$title",
          description: "$description",
          upvotes: { $size: "$upvotesBy" },
          upvotesBy: "$upvotesBy",
          isUpvoted: { $in: [req.query.userId, "$upvotesBy"] },
          isPinned: {
            $cond: {
              if: { $gte: [{ $size: "$upvotesBy" }, 3] },
              then: true,
              else: false
            }
          },
          file: "$file",
          createdAt: {
            $dateToString: {
              format: "%H:%M %d-%m-%Y",
              timezone: "+01",
              date: "$createdAt"
            }
          },
          id: "$_id"
        }
      }
    },
    { $sort: { "_id.isPinned": -1, "_id.createdAt": -1 } }
])

Answer 1

Although this is old thread, but I hope whoever found this thread can now safely for doing multi stage/pipeline aggregation(not quite sure what it's call) in MongoRepository. As I'm also struggling looking for clue and example of aggregation in mongo repository without mongo template.

But now, I'm able to do the Aggregation pipeline as per spring doc said in here

My aggregation looks like this in mongoshell:

db.getCollection('SalesPo').aggregate([
    {$project: {
        month: {$month: '$poDate'},
        year: {$year: '$poDate'},
        amount: 1,
        poDate: 1
     }},
      {$match: {$and : [{year:2020} , {month:7}] 
     }}
      ,
      {$group: { 
          '_id': {
            month: {$month: '$poDate'},
            year: {$year: '$poDate'} 
          },
          totalPrice: {$sum: {$toDecimal:'$amount'}},
          }
      },
    {$project: {
        _id: 0,
        totalPrice: {$toString: '$totalPrice'}
     }}
 ])

While I transform it into @Aggregation annotation in MongoRepository become like this below (I'm removing the aposthrephe and also replace with method params):

@Repository
public interface SalesPoRepository extends MongoRepository<SalesPo, String> {

@Aggregation(pipeline = {"{$project: {
" +
        "        month: {$month: $poDate},
" +
        "        year: {$year: $poDate},
" +
        "        amount: 1,
" +
        "        poDate: 1
" +
        "     }}"
        ,"{$match: {$and : [{year:?0} , {month:?1}] 
" +
        "     }}"
        ,"{$group: { 
" +
        "          '_id': {
" +
        "            month: {$month: $poDate},
" +
        "            year: {$year: $poDate} 
" +
        "          },
" +
        "          totalPrice: {$sum: {$toDecimal:$amount}},
" +
        "          }
" +
        "      }"
    ,"{$project: {
" +
        "        _id: 0,
" +
        "        totalPrice: {$toString: $totalPrice}
" +
        "     }}"})
    AggregationResults<SumPrice> sumPriceThisYearMonth(Integer year, Integer month);

My Document looks like this:

@Document(collection = "SalesPo")
@Data
public class SalesPo {
  @Id
  private String id;
  @JsonSerialize(using = LocalDateSerializer.class)
  private LocalDate poDate;
  private BigDecimal amount;
}

And the SumPrice class for hold the projections:

@Data
public class SumPrice {
  private BigDecimal totalPrice;
}

I hope this answer can help whoever try to do aggregation in mongorepository without using mongotemplate.