Getting Started

An easy way to bootstrap setting up a working environment is to create a Spring-based project via start.spring.io or create a Spring project in Spring Tools.

Examples Repository

The GitHub spring-data-examples repository hosts several examples that you can download and play around with to get a feel for how the library works.

Hello World

First, you need to set up a running MongoDB server. Refer to the MongoDB Quick Start guide for an explanation on how to startup a MongoDB instance. Once installed, starting MongoDB is typically a matter of running the following command: /bin/mongod

Then you can create a Person class to persist:

package org.springframework.data.mongodb.example;

public class Person {

	private String id;
	private String name;
	private int age;

	public Person(String name, int age) {
		this.name = name;
		this.age = age;
	}

	public String getId() {
		return id;
	}

	public String getName() {
		return name;
	}

	public int getAge() {
		return age;
	}

	@Override
	public String toString() {
		return "Person [id=" + id + ", name=" + name + ", age=" + age + "]";
	}
}

You also need a main application to run:

Imperative
Reactive

package org.springframework.data.mongodb.example;

import static org.springframework.data.mongodb.core.query.Criteria.*;

import org.springframework.data.mongodb.core.MongoOperations;
import org.springframework.data.mongodb.core.MongoTemplate;

import com.mongodb.client.MongoClients;

public class MongoApplication {

	public static void main(String[] args) throws Exception {

		MongoOperations mongoOps = new MongoTemplate(MongoClients.create(), "database");
		mongoOps.insert(new Person("Joe", 34));

		System.out.println(mongoOps.query(Person.class).matching(where("name").is("Joe")).firstValue());

		mongoOps.dropCollection("person");
	}
}

package org.springframework.data.mongodb.example;

import static org.springframework.data.mongodb.core.query.Criteria.*;

import org.springframework.data.mongodb.core.ReactiveMongoOperations;
import org.springframework.data.mongodb.core.ReactiveMongoTemplate;

import com.mongodb.reactivestreams.client.MongoClients;

public class ReactiveMongoApplication {

	public static void main(String[] args) throws Exception {

		ReactiveMongoOperations mongoOps = new ReactiveMongoTemplate(MongoClients.create(), "database");

		mongoOps.insert(new Person("Joe", 34))
			.then(mongoOps.query(Person.class).matching(where("name").is("Joe")).first())
			.doOnNext(System.out::println)
			.block();

		mongoOps.dropCollection("person").block();
	}
}

When you run the main program, the preceding examples produce the following output:

10:01:32,265 DEBUG o.s.data.mongodb.core.MongoTemplate - insert Document containing fields: [_class, age, name] in collection: Person
10:01:32,765 DEBUG o.s.data.mongodb.core.MongoTemplate - findOne using query: { "name" : "Joe"} in db.collection: database.Person
Person [id=4ddbba3c0be56b7e1b210166, name=Joe, age=34]
10:01:32,984 DEBUG o.s.data.mongodb.core.MongoTemplate - Dropped collection [database.person]

Even in this simple example, there are few things to notice:

You can instantiate the central helper class of Spring Mongo, MongoTemplate, by using the standard or reactive MongoClient object and the name of the database to use.
The mapper works against standard POJO objects without the need for any additional metadata (though you can optionally provide that information. See here.).
Conventions are used for handling the id field, converting it to be an ObjectId when stored in the database.
Mapping conventions can use field access. Notice that the Person class has only getters.
If the constructor argument names match the field names of the stored document, they are used to instantiate the object