Building a REST Service with Spring Boot and MongoDB (Part 1)
I’ve decided to learn Spring Boot after using the previous versions of Spring for years. I realized that Spring Boot makes a lot of things pretty easy. Besides, it reduces the complexity of your dependencies. All you need to do is run your application.
In this tutorial, I will explain “how to develop a REST service with Spring Boot and MongoDB”.
- Spring Boot and Spring Data projects which are used for developing REST APIs are used here.
- Maven is used to automating the build process.
- A typical domain-driven development approach is used, separating model, repository, service, and controller classes.
You can download the project source code from this GitHub link.
Technologies and Tools
The tutorial here uses IntelliJ IDEA, Maven, and Postman for coding, building, and REST API testing. I’m running on Windows 10 using PowerShell.
All software is written in Java, with Spring 5.1 and Spring Boot 2.1.4. MongoDB 4.0.9 Community Server is used for persistence.
From here, I’ll assume you have JDK 8.0, IntelliJ, Maven, MongoDB, and Postman installed.
Student Information Service
This REST service brings student information and allows you to add new students to the system or remove students from the system.
My goal here is to show how the REST services will be developed using these technologies in a simple way without shuffling the business logic.
- A POST operation is used to add students to the system.
- GET operations are used to get students by student number or email. Students are also brought according to their GPAs.
- The student's collection in the MongoDB database has the data about each student’s name, student number, email, course list and GPA.
- Everything stored, received, and returned by the service is formatted as JSON.
Step 1: Spring Initialzr
If you want to create a new Spring application, you can use the Spring Initalizr. I entered the values for this project as in the picture below.
- Select Maven Project, Java, and Spring Boot 2.1.4.
- Pick an appropriate group and artifact.
- The two dependencies: MongoDB and Web.
After doing that, you can download a template project as .zip file with the “Generate Project” button.
Unzip the project and import it into IntelliJ. After doing that, you will see something like the picture below.
Step 2: Model and Repository
Student Model
A Student has six fields: id, name, studentNumber, email, courseList and gpa.
@Document annotation is used for the same purpose with @Entity annotation in JPA.
For more information about Spring Data MongoDB, you can use this link. You can read the document for the version you want. For this tutorial, the version of Spring Data MongoDB is 2.1.6.
After doing that, you can add the StudentDTO class like below. We use this in the controller layer for communicating front-end or any different consumers.
Student Repository
With the Spring Data project, you will have magic when you create an interface that extends MongoRepository. The magic is shown below. There is no need to implement this interface :).
Student repository interface has three methods. Firs two methods find the student by its student number or email. The last method sorts students according to their GPA.
Step 3: Student Service
Now, we create the student service that the student controller will call. The student service has six methods. Simply, these methods list students according to some criteria, save a student, update a student and delete a student.
Normally, controller classes talk with the methods in repository classes directly, there is nothing wrong. But, if we need to some business logic, we should not write this code block in the controller. Because of this, the service layer is needed.
Step 4: REST Controller
Finally, we can create the REST controller. This controller has four @GetMapping, one @PostMapping and one @DeleteMapping.
Step 5: Database Configuration
To connect to the MongoDB database, edit the settings in the “application.properties” file which is part of “resources”. The following configurations are sufficient because there is no authentication in the database currently.
Running the Service and Testing with Postman
To run the service and test it in Postman, first, we need to run MongoDB. For this, two commands are required.
After doing that, we can run the project to test the REST service.
After running the project, you can test the REST service. For this, open Postman, enter the URL and select GET method like below.
You can add a student to the system with POST method in Postman. First, you should enter Content-Type : application/json header key-value pair. Second, in body tab, you must enter the student information that you want to save the database in JSON format.
If you want to delete a student, you should select DELETE method in Postman and add a student number that you want to delete to the end of the link.
After doing the steps above, you should see two records in the database like below.
Note: This tutorial focuses on the combination of Spring Data, MongoDB, and REST API. There is no validation for object fields in the project.
Please click on the link below to learn how to write a unit test using Spring Boot.
