Create a Spring Boot Application

1 Generate the Spring Boot Project

Open your browser and navigate to https://start.spring.io.

Use the following settings:

Click ADD DEPENDENCIES and add:

• Spring Web

Click GENERATE to download the project ZIP file.

2 Extract and Open the Project

1. Locate library-system.zip in your Downloads folder.
2. Extract the ZIP file.
3. Open the extracted project in IntelliJ IDEA IDE.
4. Allow Gradle to import the project and download its dependencies.
5. Wait until the project is fully synchronized before continuing.

3 Examine the Project Structure

Confirm that your project has a structure similar to this:

Locate the main application class:

package com.example.librarysystem;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class LibrarySystemApplication {

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

4 Review the Spring Web Dependency

Open build.gradle which contains the Gradle build configuration including the list of dependencies that your project requires. Scroll down and find the Spring Web dependency. It should contain something similar to:

dependencies {
                implementation 'org.springframework.boot:spring-boot-starter-web'

                testImplementation 'org.springframework.boot:spring-boot-starter-test'
            }

The spring-boot-starter-web dependency provides the infrastructure needed to build web applications and REST-style HTTP endpoints with Spring Boot.

5 Configure the Application Port

Open: src/main/resources/application.properties

This file contains the configuration properties for the Spring Boot application, such as which port the application uses, database settings, etc. Add the following:

spring.application.name=library-system
                    server.port=8080

The first property gives the application a name. The second tells Spring Boot to listen for HTTP requests on port 8080.

6 Create the Controller class

Inside: src/main/java/com/example/librarysystem

Create a new class named:

Your structure should now look like:

In the BooksController.java file, enter the following code:

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class BooksController {

    @GetMapping("api/v1/books")
    public String getBooks() {
        return "Here is the List of books";
    }
}

Study the code carefully.

8 Run the Application

You can run the application with Intellij IDEA by clicking the "Run" button. In this activity, we will learn how to run the application using commands in the terminal. You can use the windows command prompt or PowerShell terminal by running "cmd" command in windows search bar. You can also use the terminal in IntelliJ IDEA by clicking the "Terminal" tab at the bottom of the IDE as shown in the figure.

Navigate to the project root directory where build.gradle is located.

On Windows:

Watch the console. You should eventually see a message similar to:

Started LibrarySystemApplication in X.XXX seconds

9 Test Your First HTTP Endpoint

Recall that these URL endpoints can be called by other applications or tools. In particular, most of the time they will be called by a web browser. You can test the endpoint by opening a web browser and entering the following URL:

By default this will make an HTTP request with a GET method. We will learn more about other HTTP methods later. You should see:

You have just created your first Spring Boot HTTP endpoint.

10 Add a Second Endpoint

Now modify BooksController and add a second method:

@GetMapping("api/v1/welcome")
public String welcome() {
    return "Welcome to my Spring Boot application!";
}

The complete controller should now contain two endpoints:

package com.example.librarysystem.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class BooksController {

    @GetMapping("api/v1/books")
    public String getBooks() {
        return "Here is the List of books";
    }

    @GetMapping("api/v1/welcome")
    public String welcome() {
        return "Welcome to my Spring Boot application!";
    }
}

Test the new endpoint:

You should receive: Welcome to my Spring Boot application!

11 Create an Endpoint with a Path Variable

Next, create an endpoint that uses part of the URL as input. To do this, you will use a path variable. A path variable is a placeholder in the URL that can be replaced with actual values when making a request. In the code, you will use @PathVariable annotation to extract the value from the URL and pass it to the method.

Add this method to the controller class:

@GetMapping("api/v1/hello/{name}")
public String helloName(@PathVariable String name) {
    return "Hello, " + name + "!";
}

Test it with:

The response should be:

Try another name:

The response should change accordingly:

13 Test All Endpoints

Test each URL and record the response.

14 Stop the Application

Return to the terminal and press Ctrl+C. The embedded server will stop and the application will terminate.