Mapping mongo db query to spring

Question

I know this question has been asked a million times before here, but I cannot find anything matching my use case. Probably due to lack of knowledge of the Spring Mongo aggregation framework. I hope someone can shed some light on the subject for me.

Mongo shell aggregation

db.mongoAuditEvent.aggregate([ 
    {$group: {_id : "$corrId", currentEvent: {"$last": "$event.status"}, events: { $push: "$$ROOT"} }}, 
    {$sort: {"timestamp": 1} }, 
    {$skip: 0 }, 
    {$limit: 10}
], {allowDiskUse: true}).pretty()

Produces

{
  "_id" : "00aa9c60-2950-439b-976e-0980da829981",
  "currentEvent" : "UPSTREAM_QUEUE",
  "events" : [
    {
      "_id" : "e746cd3f-dfe3-47b3-a1d0-3342adaf61c3",
      "_class" : "no.fint.audit.plugin.mongo.MongoAuditEvent",
      "corrId" : "00aa9c60-2950-439b-976e-0980da829981",
      "source" : "employee",
      "timestamp" : NumberLong("1484478431288"),
      "event" : {
        "corrId" : "00aa9c60-2950-439b-976e-0980da829981",
        "action" : "GET_ALL_EMPLOYEES",
        "status" : "DOWNSTREAM_QUEUE",
        "time" : NumberLong("1484478431287"),
        "source" : "employee",
        "client" : "CACHE_SERVICE"
      },
      "clearData" : true
    }
  ]
}

I managed to translate this to the following in Spring:

public List<DBObject> getAllAuditEvents(Integer page, Integer pageSize) {
    List<DBObject> agg = new ArrayList();
    agg.add(BasicDBObject.parse("{$group: {_id: \"$corrId\", currentEvent: {\"$last\": \"$event.status\"}, events: { $push: \"$$ROOT\"} }}"));
    agg.add(BasicDBObject.parse("{$sort: {\"timestamp\": -1} }"));
    agg.add(BasicDBObject.parse("{$limit: " + pageSize + "}"));
    agg.add(BasicDBObject.parse("{$skip: " + (page * pageSize) + " }"));
    return (List<DBObject>) mongoTemplate.getCollection("mongoAuditEvent")
        .aggregate(agg).results();
}

But this fails because I have not specified the allowDiskUse:true option anywhere, and I cannot seem to find the right place to specify it.

Then I saw that there's a more preferred way of specifying aggregations:

public List<MongoAuditEventGroup> getAllAuditEvents(Integer page, Integer pageSize) {
    return mongoTemplate.aggregate(
        Aggregation.newAggregation(
            Aggregation.group("corrId"),
            Aggregation.sort(Sort.Direction.DESC, "corrId"),
            Aggregation.limit(pageSize),
            Aggregation.skip((long)page * pageSize)
        ).withOptions(newAggregationOptions().allowDiskUse(true).build()),
            MongoAuditEvent.class, 
            MongoAuditEventGroup.class).getMappedResults();
}

But I cannot seem to wrap my head around how to add the currentEvent to the group.

I would be very grateful for any help or pointers anybody could give me here.

s7vr · Accepted Answer · 2017-01-26 14:20:09Z

1

I'm going off your Mongo Shell Query. You can try something like this.

import static org.springframework.data.domain.Sort.Direction.ASC;
import static org.springframework.data.mongodb.core.aggregation.Aggregation.*;

Aggregation agg = newAggregation(
                group("corrId").last("event.status").as("currentEvent").push("$$ROOT").as("events"),
                sort(ASC, "timestamp"),
                skip(0L),
                limit(10L)).
                withOptions(newAggregationOptions().allowDiskUse(true).build());

List<MongoAuditEventGroup> results =  mongoTemplate.aggregate(agg, MongoAuditEvent.class, 
        MongoAuditEventGroup.class).getMappedResults();

answered Jan 26, 2017 at 14:20

s7vr

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2 Comments

Øystein Amundsen Over a year ago

That worked. :-) Thank you! But this leaves me with the issue of No serializer found for my output class. What am I missing here?

Øystein Amundsen Over a year ago

Nevermind. Forgot getters/setters on the properties of the output class. Again, thank you!

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