MongoDB

https://github.com/spring-boot-tutorials/spring-data-mongodb

In this article we will configure Spring Boot to connect to a MongoDB database.

MongoDB Server

Install and run MongoDB server

brew update
brew install mongodb-community
brew services start mongodb-community

Create Initial Code Base

Go to https://start.spring.io/
Click Add Dependencies, search for mongodb, then add
Click Add Dependencies, search for Lombok, then add
Click Generate

Dependencies

Dependencies used in pom.xml

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.38</version>
</dependency>
<dependency>
    <groupId>org.instancio</groupId>
    <artifactId>instancio-junit</artifactId>
    <version>5.4.0</version>
</dependency>

Properties

In src/main/resources/application.properties let’s add the following properties so the Spring Boot application can connect to the database

spring.data.mongodb.host=localhost
spring.data.mongodb.port=27017

Model

Let’s create a new POJO src/main/java/com/example/mongodb/Author.java

Data
@SuperBuilder
@Document(collection = "authors")
@NoArgsConstructor
class Author {
    @Id
    @Indexed(unique = true)
    @Field(name = "_id")
    private String id = UUID.randomUUID().toString();

    @Field(name = "full_name")
    private String name;

    @Indexed(unique = true)
    private String email;

    @Field(name = "num_articles")
    private Integer articleCount;

    private Boolean active;

    public Boolean isActive() {
        return this.active;
    }
}

Repository

Next we will create a Spring repository to CRUD against the database.

This file will be called src/main/java/com/example/AuthorRepository.java

interface AuthorRepository extends MongoRepository<Author, String> {
    Optional<Author> findByEmail(String email);

    List<Author> findByActiveTrueAndArticleCountGreaterThanEqual(int articleCount);

    @Query("{ 'num_articles': { $gte: ?0, $lte: ?1 }, 'active': true }")
    List<Author> findActiveAuthorsInArticleRange(int minArticles, int maxArticles);

    // Returns active authors JUST email
    @Query(value = "{ 'active': true }", fields = "{ 'email': 1 }")
    List<Author> findActiveAuthorEmails();
}

Main

Now let’s use this repository.

Go back to MainApplication.java and add the following:

@SpringBootApplication
@EnableMongoRepositories(basePackages = "com.example")
public class MainApplication implements CommandLineRunner {

    public static void main(String[] args) {
            SpringApplication.run(MainApplication.class, args);
    }

    @Autowired
    AuthorRepository authorRepository;

    @Autowired
    MongoTemplate mongoTemplate;

    @Override
    public void run(String... args) throws Exception {
            authorRepository.deleteAll();

            // 1. Save
            Author author = authorRepository.save(
                            Author.builder()
                                            .name("Marcus Chiu")
                                            .email("marcuschiu9@gmail.com")
                                            .articleCount(15)
                                            .active(true)
                                            .build()
            );
            System.out.println(author);

            // 2. FindAll
            List<Author> authors = authorRepository.findAll();
            authors.forEach(System.out::println);

            // 3. Paging & Sorting
            int authorCount = 10;
            authors = Instancio.ofList(Author.class)
                            .size(authorCount)
                            .create();
            authorRepository.saveAll(authors);

            Sort sort = Sort.by("name").ascending();
            PageRequest pageRequest = PageRequest.of(0, 5, sort);
            List<Author> retrievedAuthors = authorRepository.findAll(pageRequest)
                            .getContent();
            System.out.println("3. Paging & Sorting");
            retrievedAuthors.forEach(System.out::println);

            // 4. Derived Query Methods
            Optional<Author> oAuthor = authorRepository.findByEmail("marcuschiu9@gmail.com");
            System.out.println("4a. " + oAuthor.get());
            authors = authorRepository.findByActiveTrueAndArticleCountGreaterThanEqual(1000);
            System.out.println("4b. ");
            authors.forEach(System.out::println);

            // 5. Custom Query Methods
            authors = authorRepository.findActiveAuthorsInArticleRange(0, 5000);
            System.out.println("5. ");
            authors.forEach(System.out::println);

            // 6. MongoTemplate
            author = Instancio.create(Author.class);
            Author savedAuthor = mongoTemplate.insert(author);
            Author retrievedAuthor = mongoTemplate.findById(savedAuthor.getId(), Author.class);
            System.out.println("6. " + retrievedAuthor);

            // 7. Complex Queries
            author = Instancio.of(Author.class)
                            .set(field(Author::isActive), false)
                            .generate(field(Author::getEmail), gen -> gen.text().pattern("#a#a#a@baeldung.com"))
                            .create();
            mongoTemplate.save(author);
            Criteria nonActive = Criteria.where("active").is(false);
            Criteria baeldungEmail = Criteria.where("email").regex("@baeldung\\.com$");
            Query query = new Query();
            query.addCriteria(nonActive);
            query.addCriteria(baeldungEmail);
            retrievedAuthors = mongoTemplate.find(query, Author.class);
            System.out.println("7. Complex Queries");
            retrievedAuthors.forEach(System.out::println);

            // 8. Update Queries
            authorRepository.save(Author.builder().name("Jigglypuff").build());
            query = new Query(Criteria.where("name").is("Jigglypuff"));
            Update update = new Update();
            update.set("active", false);
            UpdateResult updateResult = mongoTemplate.updateFirst(query, update, Author.class);
            assertThat(updateResult.getModifiedCount()).isEqualTo(1);

            // 9. Upsert
            UUID authorId = UUID.randomUUID();
            String email = RandomString.make() + "@baeldung.com";
            String name = RandomString.make();
            query = new Query(Criteria.where("email").is(email));
            update = new Update()
                            .set("name", name)
                            .setOnInsert("id", authorId)
                            .setOnInsert("active", true);
            mongoTemplate.upsert(query, update, Author.class);
            retrievedAuthor = mongoTemplate.findOne(query, Author.class);
            assertThat(retrievedAuthor).isNotNull();
    }
}

Run Application

Open terminal at project root and execute the following:

mvn spring-boot:run

There should be no errors and the output will display all the CRUD operations.