Mongodb $lookup in Spring data mongo

user_4527793 0
Viewed 31972

I'm a new Mongodb and I have a problem with $lookup with java spring.

I would like to use this shell in Spring data 

db.NewFeed.aggregate([
    {
        $match : {username : "user001"}
    },
    {
      $lookup:
        {
          from: "NewfeedContent",
          localField: "content.contentId",
          foreignField: "_id",
          as: "NewfeedContent"
        }
   }
])

I found on Google but no answer yet.

spring-mongo mongodb java
5 Answers

Here is an example:

Collection posts 

{
"_id" : ObjectId("5a198074ed31adaf5d79fe8a"),
"title" : "Post 1",
"authors" : [1, 2]
},
{
"_id" : ObjectId("5a198074ed31adaf5d79fe8d"),
"title" : "Post 2",
"authors" : [2]
}

Collection users 

{
"_id" : ObjectId("5a18b483ed31ada08fd6ed82"),
"userId" : 1,
"name" : "Vinod Kumar"
},
{
"_id" : ObjectId("5a18b483ed31ada08fd6ed83"),
"userId" : 2,
"name" : "Jim Hazel"
},
{
"_id" : ObjectId("5a18b483ed31ada08fd6ed84"),
"userId" : 3,
"name" : "Alex Wong"
}

Mongodb query with lookup and match

db.users.aggregate([
{
  $lookup:
    {
      from: "users",
      localField: "userid",
      foreignField: "authors",
      as: "post"
    }
  },
  {
     $match: { "post": { $ne: [] } }
  }
]).pretty()

Spring Mongoopration syntax

LookupOperation lookupOperation = LookupOperation.newLookup().
            from("posts").
            localField("userid").
            foreignField("authors").
            as("post");

AggregationOperation match = Aggregation.match(Criteria.where("post").size(1));


Aggregation aggregation = Aggregation.newAggregation(lookupOperation, match);

List<BasicDBObject> results = mongoOperation.aggregate(aggregation, "users", BasicDBObject.class).getMappedResults();
user_16144280

Its too late to answer this, but it might helps other who are facing the same issue. If you are using spring-boot-data-mongodb-2.0 or above version then there is a easy way to implement this.

AggregationOperation match = Aggregation.match(Criteria.where("username").is("user001")));
AggregationOperation query = Aggregation.lookup("NewfeedContent", "content.contentId", "_id", "NewfeedContent");
// If you want to unwind
//AggregationOperation unwind = Aggregation.unwind("Patient");
Aggregation agr = Aggregation.newAggregation(query, match, unwind);
AggregationResults<Document> result = springTemplate.aggregate(agr, "CollectionName", Document.class);
user_48017270

Can use below to join 3 Collections

MongoClient mongoClient = new MongoClient( "localhost" , 27017 );

DB db = mongoClient.getDB( "DBname" );

BasicDBObject query = BasicDBObject.parse("{$match:{_id:61188}},\n" +
        "   {\n" +
        "     $lookup:\n" +
        "       {\n" +
        "         from: \"CustomerDetails\",\n" +
        "         localField: \"supplierId\",\n" +
        "         foreignField: \"supplierId\",\n" +
        "         as: \"newfield\"\n" +
        "       }\n" +
        "  }\n" +
        "  ,  {\n" +
        "     $lookup:\n" +
        "       {\n" +
        "         from: \"ItemDetails\",\n" +
        "         localField: \"supplierId\",\n" +
        "         foreignField: \"supplierId\",\n" +
        "         as: \"newfield\"\n" +
        "       }\n" +
        "  }");

AggregationOutput dumps = db.getCollection("HeaderInfo").aggregate(query);

System.out.println("result="+dumps.results());
user_113283520
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