How to Build a Reusable MongoDB Utility Class in Java

MongoBase utility class

The MongoBase class provides a set of static helper methods for building MongoDB connections without external frameworks. It abstracts the creation of ServerAddress, MongoCredential, MongoClient, MongoDatabase, and MongoCollection objects, and also supplies a method to close the client.

package com.fun.mongodb;
import com.fun.frame.SourceCode;
import com.mongodb.MongoClient;
import com.mongodb.MongoClientURI;
import com.mongodb.MongoCredential;
import com.mongodb.ServerAddress;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import org.bson.Document;
import java.util.Arrays;
import java.util.List;

public class MongoBase extends SourceCode {
    public static List<ServerAddress> getServers(ServerAddress... addresses) {
        return Arrays.asList(addresses);
    }
    public static ServerAddress getServerAdress(String host, int port) {
        return new ServerAddress(host, port);
    }
    public static List<MongoCredential> getCredentials(MongoCredential... credentials) {
        return Arrays.asList(credentials);
    }
    public static MongoCredential getMongoCredential(String userName, String database, String password) {
        return MongoCredential.createCredential(userName, database, password.toCharArray());
    }
    public static MongoClient getMongoClient(List<ServerAddress> addresses, List<MongoCredential> credentials) {
        return new MongoClient(addresses, credentials);
    }
    public static MongoDatabase getMongoDatabase(MongoClient client, String dbName) {
        return client.getDatabase(dbName);
    }
    public static MongoCollection<Document> getMongoCollection(MongoDatabase db, String collName) {
        return db.getCollection(collName);
    }
    public static void MongoOver(MongoClient client) {
        client.close();
    }
    public static MongoClient getMongoClient(MongoObject obj) {
        return new MongoClient(
            getServers(getServerAdress(obj.host, obj.port)),
            getCredentials(getMongoCredential(obj.user, obj.database, obj.password))
        );
    }
    public static MongoClient getMongoClientOnline(MongoObject obj) {
        String uri = String.format(
            "mongodb://%s:%s@%s:%d/%s",
            obj.user, obj.password, obj.host, obj.port, obj.database
        );
        return new MongoClient(new MongoClientURI(uri));
    }
    public static MongoCollection<Document> getCollection(MongoObject obj, String collName) {
        return getMongoClient(obj).getDatabase(obj.database).getCollection(collName);
    }
    public static MongoCollection<Document> getCollectionOnline(MongoObject obj, String collName) {
        return getMongoClientOnline(obj).getDatabase(obj.database).getCollection(collName);
    }
}

MongoObject configuration class

MongoObject

extends MongoBase and stores the connection parameters (host, port, username, password, database). It offers two constructors – one that builds a client from explicit server/credential objects and another that builds a client from a MongoDB URI. The class also provides a method to obtain a collection and a method to close the underlying client.

package com.fun.mongodb;
import com.mongodb.MongoClient;
import com.mongodb.client.MongoCollection;
import org.bson.Document;

public class MongoObject extends MongoBase {
    String host;
    int port;
    String user;
    String password;
    String database;
    MongoClient mongoClient;

    public MongoObject(String host, int port, String user, String password, String database) {
        this.host = host;
        this.port = port;
        this.user = user;
        this.password = password;
        this.database = database;
        this.mongoClient = getMongoClient(this);
    }

    public MongoObject(int port, String host, String user, String password, String database) {
        this.host = host;
        this.port = port;
        this.user = user;
        this.password = password;
        this.database = database;
        this.mongoClient = getMongoClientOnline(this);
    }

    public MongoCollection<Document> getMongoCollection(String collectionName) {
        MongoClient client = getMongoClientOnline(this);
        return client.getDatabase(database).getCollection(collectionName);
    }

    public void over() {
        MongoOver(this.mongoClient);
    }

    @Override
    public MongoObject clone() {
        return new MongoObject(this.host, this.port, this.user, this.password, this.database);
    }

    public MongoObject clone2() {
        return new MongoObject(this.port, this.host, this.user, this.password, this.database);
    }
}

Typical usage

The following main method demonstrates how to instantiate a MongoObject, retrieve a collection, fetch the first document, print it, and finally close the connection.

public static void main(String[] args) {
    MongoObject ready = new MongoObject("127.0.0.1", 27017, "myUser", "myPass", "myDatabase");
    MongoCollection<Document> coll = ready.getMongoCollection("my_collection");
    Document first = coll.find().first();
    System.out.println(first);
    ready.over();
}

The printed document is a standard BSON representation, e.g.:

Document{{_id=5be4ce052ce01b21b6c26a64, user_id=5482, action_type={"gameId":2,"userId":"5482"}, client_ip=114.5.146.239, ...}}