Querydsl with MongoDB usage

I have the following Mongo configuration in a Java Spring project:

    @Configuration
public class MongoConfiguration {

    public static int allocateRandomPort() {
        try {
            ServerSocket server = new ServerSocket(0);
            int port = server.getLocalPort();
            server.close();
            return port;
        } catch (IOException e) {
            throw new RuntimeException("Failed to acquire a random free port", e);
        }
    }

    @Bean
    public Mongo mongo() throws IOException {
        System.setProperty("DB.TRACE", "true");
        return new EmbeddedMongoBuilder()
                .version("2.6.0")
                .bindIp("127.0.0.1")
                .port(allocateRandomPort())
                .build();
    }
}

To start building queries using the Querydsl Mongodb module, the documentation says that:

Morphia morphia;
Datastore datastore;
// ...
QUser user = new QUser("user");
MorphiaQuery<User> query = new MorphiaQuery<User>(morphia, datastore, user);

I have no ideia on how to create the instance of the MorphiaQuery class. Should the Datastore object be a inject Mongo instance? And how about Morphia object? Other tutorials I found online create the instance as:

Morphia morphia = new Morphia()
        .map(Book.class, Author.class, Tag.class);

I would like to build the queries inside a Spring Data MongoDB repository. Is there a fully functional example somewhere?

Thanks.