retrieve distinct values - mongodb

Question

i have already created a project in spring boot and i can retrieve data from my mongodb database using mongo repository.

i want to write a query in my spring boot app that allows me to get distinct values of an attribute for a given value of another attribute.

Example

 tag1 | tag2  |  tag3
 mod  | test  |  v1
 mod1 | test1 |  v2
 mod1 | test1 |  v3
 mod1 | test1 |  v4

expected: when i call method findbyTag1 ( String tag1) using value mod1 for tag1 variable i want to get distinct values of tag2. In this case the result would be test1.

is there any solution?

notionquest · Accepted Answer · 2017-07-13 16:16:43Z

MongoDB Query:-

db.tags.distinct("tag2",{"tag1" : "mod1"});

Equivalent Java Code:-

Please change the database and collection name accordingly.

import org.bson.Document;

import com.mongodb.MongoClient;
import com.mongodb.client.DistinctIterable;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import com.mongodb.client.model.Filters;

public class GetDistinctTagsValues {
    public static void main(String[] args) {

        MongoClient client = new MongoClient();

        MongoDatabase database = client.getDatabase("test");

        MongoCollection<Document> collection = database.getCollection("tags");

        DistinctIterable<String> collectionData = collection.distinct("tag2", Filters.eq("tag1", "mod1"), String.class);

        for (String doc : collectionData) {
            System.out.println(doc);
        }

        client.close();

    }

}

Dependency:-

    <dependency>
        <groupId>org.mongodb</groupId>
        <artifactId>mongo-java-driver</artifactId>
        <version>3.4.2</version>
    </dependency>

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