Spring-Mongo Template Pagination

1. Introduction

In this blog, we will be creating a sample project where we would use the spring mongo template for pagination. By default, the spring-mongo template has no method for pagination.

2. Spring Data

Spring Data is an umbrella project which contains many submodules, each specific to a particular database. In this article, we’ll be covering the Spring-Mongo template for fetching the records with pagination.

3. MongoDB

MongoDB is a document-oriented NoSQL database that stores JSON-like documents with dynamic schemas. It is commonly used for high volume data storage.

4. Setup

In this section, we will quickly set up a project using Spring Initializr. Using this tool, we can quickly provide a list of Dependencies we need and download the bootstrapped application:

5. Maven Dependencies

Here is the pom.xml file, you should see the below dependencies added:

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-mongodb</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter-data-mongodb</artifactId>

</dependency>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter-web</artifactId>

</dependency>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter-test</artifactId>

<groupId>org.junit.vintage</groupId>

<artifactId>junit-vintage-engine</artifactId>

</exclusion>

</exclusions>

</dependency>

</dependencies>

6. User Entity

In this section, we will make a simple User entity with some fields to demonstrate simple MongoDB queries:

@Document(collection = "user")
public class User {

    @Id
    private String id;

    private String userName;

    private String firstName;

    private String lastName;

    private String email;

    ...

}

@Document(collection = "user")

public class User {

@Id

private String id;

private String userName;

private String firstName;

private String lastName;

private String email;

...

}

7. Repository

Now let’s define a custom data layer interface:

public interface UserCustomRepository {

    Page<User> findUsers(Pageable pageable);
}

public interface UserCustomRepository {

Page<User> findUsers(Pageable pageable);

}

8. Implementing Repository

Now let’s implement the above data layer interface. We will make use of Mongo Template bean which is initialized by Spring Boot. Below is the implementation class:

@Repository
public class UserRepositoryImpl implements UserCustomRepository {

    private final MongoTemplate mongoTemplate;

    public UserRepositoryImpl(MongoTemplate mongoTemplate) {
        this.mongoTemplate = mongoTemplate;
    }
    
    ...    
}

@Repository

public class UserRepositoryImpl implements UserCustomRepository {

private final MongoTemplate mongoTemplate;

public UserRepositoryImpl(MongoTemplate mongoTemplate) {

this.mongoTemplate = mongoTemplate;

}

...

}

9. Using Paginated Queries

Now let’s have a look at the pagination queries using Mongo Template. We had used PageableExecutionUtils class of Spring Data for pagination.

    @Override
    public Page<User> findUsers(Pageable pageable) {
        Query query = new Query();
        long count = this.mongoTemplate.count(query, User.class);

        query.with(pageable);
        List<User> users = mongoTemplate.find(query, User.class);
        return PageableExecutionUtils.getPage(users, pageable, () -> count);
    }

@Override

public Page<User> findUsers(Pageable pageable) {

Query query = new Query();

long count = this.mongoTemplate.count(query, User.class);

query.with(pageable);

List<User> users = mongoTemplate.find(query, User.class);

return PageableExecutionUtils.getPage(users, pageable, () -> count);

}

10. Conclusion

In this quick tutorial, we saw how we can use pagination in custom queries using Mongo Template. The source code for this application is available over on GitHub.