Quarkus - Using the MongoDB Client

MongoDB is a well known NoSQL Database that is widely used.

In this guide, we see how you can get your REST services to use the MongoDB database.

Prerequisites

To complete this guide, you need:

  • less than 15 minutes

  • an IDE

  • JDK 1.8+ installed with JAVA_HOME configured appropriately

  • Apache Maven 3.5.3+

  • MongoDB installed or Docker installed

Architecture

The application built in this guide is quite simple: the user can add elements in a list using a form and the list is updated.

All the information between the browser and the server are formatted as JSON.

The elements are stored in MongoDB.

Solution

We recommend that you follow the instructions in the next sections and create the application step by step. However, you can go right to the completed example.

Clone the Git repository: git clone https://github.com/quarkusio/quarkus-quickstarts.git, or download an archive.

The solution is located in the mongo-client directory.

Creating the Maven project

First, we need a new project. Create a new project with the following command:

mvn io.quarkus:quarkus-maven-plugin:0.19.1:create \
    -DprojectGroupId=org.acme \
    -DprojectArtifactId=using-mongodb-client \
    -DclassName="org.acme.rest.json.FruitResource" \
    -Dpath="/fruits" \
    -Dextensions="resteasy-jsonb,mongodb-client"

This command generates a Maven structure importing the RESTEasy/JAX-RS, JSON-B and MongoDB Client extensions. After this, the quarkus-mongodb-client extension has been added to your pom.xml.

Creating your first JSON REST service

In this example, we will create an application to manage a list of fruits.

First, let’s create the Fruit bean as follows:

package org.acme.rest.json;

import java.util.Objects;

public class Fruit {

    private String name;
    private String description;

    public Fruit() {
    }

    public Fruit(String name, String description) {
        this.name = name;
        this.description = description;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    @Override
    public boolean equals(Object obj) {
        if (!(obj instanceof Fruit)) {
            return false;
        }

        Fruit other = (Fruit) obj;

        return Objects.equals(other.name, this.name);
    }

    @Override
    public int hashCode() {
        return Objects.hash(this.name);
    }
}

Nothing fancy. One important thing to note is that having a default constructor is required by the JSON serialization layer.

Now create a org.acme.rest.json.FruitService that will be the business layer of our application and store/load the fruits from the mongoDB database.

package org.acme.rest.json;

import com.mongodb.client.MongoClient;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoCursor;
import org.bson.Document;

import javax.enterprise.context.ApplicationScoped;
import javax.inject.Inject;
import java.util.ArrayList;
import java.util.List;

@ApplicationScoped
public class FruitService {

    @Inject MongoClient mongoClient;

    public List<Fruit> list(){
        List<Fruit> list = new ArrayList<>();
        MongoCursor<Document> cursor = getCollection().find().iterator();

        try {
            while (cursor.hasNext()) {
                Document document = cursor.next();
                Fruit fruit = new Fruit();
                fruit.setName(document.getString("name"));
                fruit.setDescription(document.getString("description"));
                list.add(fruit);
            }
        } finally {
            cursor.close();
        }
        return list;
    }

    public void add(Fruit fruit){
        Document document = new Document()
                .append("name", fruit.getName())
                .append("description", fruit.getDescription());
        getCollection().insertOne(document);
    }

    private MongoCollection getCollection(){
        return mongoClient.getDatabase("fruit").getCollection("fruit");
    }
}

Now, edit the org.acme.rest.json.FruitResource class as follows:

@Path("/fruits")
@Produces(MediaType.APPLICATION_JSON)
@Consumes(MediaType.APPLICATION_JSON)
public class FruitResource {

    @Inject FruitService fruitService;

    @GET
    public List<Fruit> list() {
        return fruitService.list();
    }

    @POST
    public List<Fruit> add(Fruit fruit) {
        fruitService.add(fruit);
        return list();
    }
}

The implementation is pretty straightforward and you just need to define your endpoints using the JAX-RS annotations and use the FruitService to list/add new fruits.

Configuring the mongo database

The main property to configure is the URL to access to MongoDB, almost all configuration can be included in the connection URI so we advise you to do so, you can find more information in the MongoDB documentation: https://docs.mongodb.com/manual/reference/connection-string/

A sample configuration should look like this:

# configure the mongoDB client for a replica set of two nodes
quarkus.mongodb.connection-string = mongodb://mongo1:27017,mongo2:27017

In this example, we are using a single instance running on localhost:

# configure the mongoDB client for a replica set of two nodes
quarkus.mongodb.connection-string = mongodb://localhost:27017

If you need more configuration properties, there is a full list at the end of this guide.

Running a Mongo Database

As by default, MongoClient is configure to access a local Mongo database on port 27017 (the default MongoDB port), if you have a local running database on this port, there is nothing more to do before being able to test it!

If you want to use Docker to run a Mongo database, you can use the following command to launch one:

docker run -ti --rm -p 27017:27017 mongo:4.0

Creating a frontend

Now let’s add a simple web page to interact with our FruitResource. Quarkus automatically serves static resources located under the META-INF/resources directory. In the src/main/resources/META-INF/resources directory, add a fruits.html file with the content from this fruits.html file in it.

You can now interact with your REST service:

Reactive MongoDB Client

A reactive MongoDB Client is included in Quarkus. Using it is as easy as using the classic MongoDB Client. You can rewrite the previous example to use it like the following.

package org.acme.rest.json;

import io.quarkus.mongodb.ReactiveMongoClient;
import io.quarkus.mongodb.ReactiveMongoCollection;
import org.bson.Document;

import javax.enterprise.context.ApplicationScoped;
import javax.inject.Inject;
import java.util.List;
import java.util.concurrent.CompletionStage;

@ApplicationScoped
public class ReactiveFruitService {

    @Inject
    ReactiveMongoClient mongoClient;

    public CompletionStage<List<Fruit>> list(){
        return getCollection().find().map(doc -> {
            Fruit fruit = new Fruit();
            fruit.setName(doc.getString("name"));
            fruit.setDescription(doc.getString("description"));
            return fruit;
        }).toList().run();
    }

    public CompletionStage<Void> add(Fruit fruit){
        Document document = new Document()
                .append("name", fruit.getName())
                .append("description", fruit.getDescription());
        return getCollection().insertOne(document);
    }

    private ReactiveMongoCollection<Document> getCollection(){
        return mongoClient.getDatabase("fruit").getCollection("fruit");
    }
}
package org.acme.rest.json;


import javax.inject.Inject;
import javax.ws.rs.*;
import javax.ws.rs.core.MediaType;
import java.util.List;
import java.util.concurrent.CompletionStage;

@Path("/reactive_fruits")
@Produces(MediaType.APPLICATION_JSON)
@Consumes(MediaType.APPLICATION_JSON)
public class ReactiveFruitResource {

    @Inject ReactiveFruitService fruitService;


    @GET
    public CompletionStage<List<Fruit>> list() {
        return fruitService.list();
    }

    @POST
    public CompletionStage<List<Fruit>>  add(Fruit fruit) {
        fruitService.add(fruit);
        return list();
    }
}

Simplifying MongoDB Client usage using BSON codec

By using a Bson Codec, the MongoDB Client will take care of the transformation of your domain object to/from a MongoDB Document automatically.

First you need to create a Bson Codec that will tell Bson how to transform your entity to/from a MongoDB Document. Here we use a CollectibleCodec as our object is retrievable from the database (it has a MongoDB identifier), if not we would have used a Codec instead. More information in the codec documentation: https://mongodb.github.io/mongo-java-driver/3.10/bson/codecs.

package org.acme.rest.json.codec;

import com.mongodb.MongoClient;
import org.acme.rest.json.Fruit;
import org.bson.*;
import org.bson.codecs.Codec;
import org.bson.codecs.CollectibleCodec;
import org.bson.codecs.DecoderContext;
import org.bson.codecs.EncoderContext;

import java.util.UUID;

public class FruitCodec implements CollectibleCodec<Fruit> {

    private final Codec<Document> documentCodec;

    public FruitCodec() {
        this.documentCodec = MongoClient.getDefaultCodecRegistry().get(Document.class);
    }

    @Override
    public void encode(BsonWriter writer, Fruit fruit, EncoderContext encoderContext) {
        Document doc = new Document();
        doc.put("name", fruit.getName());
        doc.put("description", fruit.getDescription());
        documentCodec.encode(writer, doc, encoderContext);
    }

    @Override
    public Class<Fruit> getEncoderClass() {
        return Fruit.class;
    }

    @Override
    public Fruit generateIdIfAbsentFromDocument(Fruit document) {
        if (!documentHasId(document)) {
            document.setId(UUID.randomUUID().toString());
        }
        return document;
    }

    @Override
    public boolean documentHasId(Fruit document) {
        return document.getId() != null;
    }

    @Override
    public BsonValue getDocumentId(Fruit document) {
        return new BsonString(document.getId());
    }

    @Override
    public Fruit decode(BsonReader reader, DecoderContext decoderContext) {
        Document document = documentCodec.decode(reader, decoderContext);
        Fruit fruit = new Fruit();
        if (document.getString("id") != null) {
            fruit.setId(document.getString("id"));
        }
        fruit.setName(document.getString("name"));
        fruit.setDescription(document.getString("description"));
        return fruit;
    }
}

Then you need to create a CodecProvider to link this Codec to the Fruit class.

package org.acme.rest.json.codec;

import org.acme.rest.json.Fruit;
import org.bson.codecs.Codec;
import org.bson.codecs.configuration.CodecProvider;
import org.bson.codecs.configuration.CodecRegistry;

public class FruitCodecProvider implements CodecProvider {
    @Override
    public <T> Codec<T> get(Class<T> clazz, CodecRegistry registry) {
        if (clazz == Fruit.class) {
            return (Codec<T>) new FruitCodec();
        }
        return null;
    }

}

Quarkus takes care of registering the CodecProvider for you.

Finally, when getting the MongoCollection from the database you can use directly the Fruit class instead of the Document one, the codec will automatically map the Document to/from your Fruit class.

Here is an example of using a MongoCollection with the FruitCodec.

package org.acme.rest.json;

import com.mongodb.client.MongoClient;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoCursor;

import javax.enterprise.context.ApplicationScoped;
import javax.inject.Inject;
import java.util.ArrayList;
import java.util.List;

@ApplicationScoped
public class CodecFruitService {

    @Inject MongoClient mongoClient;

    public List<Fruit> list(){
        List<Fruit> list = new ArrayList<>();
        MongoCursor<Fruit> cursor = getCollection().find().iterator();

        try {
            while (cursor.hasNext()) {
                list.add(cursor.next());
            }
        } finally {
            cursor.close();
        }
        return list;
    }

    public void add(Fruit fruit){
        getCollection().insertOne(fruit);
    }

    private MongoCollection<Fruit> getCollection(){
        return mongoClient.getDatabase("fruit").getCollection("fruit", Fruit.class);
    }
}

Building a native executable

You can use the MongoDB client in a native executable.

If you want to use SSL/TLS encryption, you need to add these properties in your application.properties:

quarkus.mongodb.tls=true
quarkus.mongodb.tls-insecure=true #only if TLS certificat cannot be validated

You can then build a native executable with the usual command ./mvnw package -Pnative.

Running it is as simple as executing ./target/using-mongodb-client-1.0-SNAPSHOT-runner.

You can then point your browser to http://localhost:8080/fruits.html and use your application.

Currently, Quarkus doesn’t support the mongodb+srv protocol in native mode.

Conclusion

Accessing a Mongo database from a MongoDB Client is easy with Quarkus as it provides configuration and native support for it.

Connection properties

quarkus.mongodb.connection-string

(e.g. mongodb://mongo1:27017,mongo2:27017) MongoDB connection string, this is a URI where a lot of options can be passed : https://docs.mongodb.com/manual/reference/connection-string/

quarkus.mongodb.hosts

Comma separated list of hosts.

quarkus.mongodb.application-name

Application name.

quarkus.mongodb.max-pool-size

Maximum number of connections in the connection pool.

quarkus.mongodb.min-pool-size

Minimum number of connections in the connection pool.

quarkus.mongodb.max-connection-idle-time

Maximum idle time of a pooled connection. A connection that exceeds this limit will be closed.

quarkus.mongodb.max-connection-life-time

Maximum life time of a pooled connection. A connection that exceeds this limit will be closed.

quarkus.mongodb.wait-queue-timeout

The maximum wait time that a thread may wait for a connection to become available.

quarkus.mongodb.maintenance-frequency

Configures the time period between runs of the maintenance job. Default is 0.

quarkus.mongodb.maintenance-initial-delay

Configures period of time to wait before running the first maintenance job on the connection pool.

quarkus.mongodb.wait-queue-multiple

This multiplier, multiplied with the maxPoolSi setting, gives the maximum number of threads that may be waiting for a connection to become available from the pool. All further threads will get an exception right away.

quarkus.mongodb.connect-timeout

How long a connection can take to be opened before timing out.

quarkus.mongodb.socket-timeout

How long a send or receive on a socket can take before timing out.

quarkus.mongodb.tls-insecure

If connecting with TLS, this option enables insecure TLS connections. Default to false.

quarkus.mongodb.tls

Whether to connect using TLS. Default to false.

quarkus.mongodb.replica-set-name

Implies that the hosts given are a seed list, and the driver will attempt to find all members of the set.

quarkus.mongodb.server-selection-timeout

How long the driver will wait for server selection to succeed before throwing an exception.

quarkus.mongodb.local-threshold

When choosing among multiple MongoDB servers to send a request, the driver will only send that request to a server whose ping time is less than or equal to the server with the fastest ping time plus the local threshold.

quarkus.mongodb.heartbeat-frequency

The frequency that the driver will attempt to determine the current state of each server in the cluster.

quarkus.mongodb.read-preference

Configures the read preferences. Supported values are: primary|primaryPreferred|secondary|secondaryPreferred|nearest

quarkus.mongodb.max-wait-queue-size

Configures the maximum number of concurrent operations allowed to wait for a server to become available. All further operations will get an exception immediately.

Write concern

quarkus.mongodb.write-concern.safe

Configures the safety. If set to true (the default): the driver ensures that all writes are acknowledged by the MongoDB server, or else throws an exception. If set to false: the driver does not ensure that all writes are acknowledged by the MongoDB server.

quarkus.mongodb.write-concern.journal

Configures the journal writing aspect. If set to true (the default): the driver waits for the server to group commit to the journal file on disk. If set to false: the driver does not wait for the server to group commit to the journal file on disk.

quarkus.mongodb.write-concern.w

When set, the driver adds w: wValue to all write commands. It requires safe to be true. The value is typically a number, but can also be the majority string.

quarkus.mongodb.write-concern.retry-writes

If set to true, the driver will retry supported write operations if they fail due to a network error. The default is false.

quarkus.mongodb.write-concern.w-timeout

When set, the driver adds wtimeout : ms to all write commands. It requires safe to be true.

Credentials

quarkus.mongodb.credentials.username

Configures the username.

quarkus.mongodb.credentials.password

Configures the password.

quarkus.mongodb.credentials.auth-mechanism

Configures the authentication mechanism to use if a credential was supplied. The default is unspecified, in which case the client will pick the most secure mechanism available based on the sever version. For the GSSAPI and MONGODB-X509 mechanisms, no password is accepted, only the username. Supported values: MONGO-CR|GSSAPI|PLAIN|MONGODB-X509

quarkus.mongodb.credentials.auth-source

Configures the source of the authentication credentials. This is typically the database that the credentials have been created. The value defaults to the database specified in the path portion of the connection string. If the database is specified in neither place, the default value is admin. This option is only respected when using the MONGO-CR mechanism (the default).

quarkus.mongodb.credentials.auth-mechanism-properties

Allows passing authentication mechanism properties.