Configuring with YAML Files

Introduction

In this project, you will learn how to configure a Spring Boot application using a YAML file, implement a class to handle the configuration data, and create a controller to display the configured information on a web page.

👀 Preview

🎯 Tasks

In this project, you will learn:

• How to configure the application properties using a YAML file
• How to implement a Student class to handle the configuration data
• How to create a StudentController to display the configured data on a web page
• How to modify the startup class to scan all classes in the project package

🏆 Achievements

After completing this project, you will be able to:

• Use YAML files for application configuration
• Use the @ConfigurationProperties annotation to automatically bind configuration data to a class
• Use the @Value annotation to inject configuration values into a controller
• Use the @SpringBootApplication annotation to configure component scanning
• Develop a simple web application that displays the configured data

Configure the YAML File

In this step, you will learn how to configure the application properties using a YAML file. Follow the steps below to complete this step:

1. Navigate to the src/main/resources directory in your project.
2. Create a new file named application.yml.
3. In the application.yml file, add the following configuration:

## Self-defined properties
school: Stanford University

student:
  id: 2024000103
  name: Taylor Joy
  age: 18
  courseId: 100018, 321001, 458911

This YAML configuration defines the school property and the student properties, including the student ID, name, age, and course IDs.

Implement the Student Class

In this step, you will implement the Student class to handle the configuration data.

1. Navigate to the org.labex.entity package and create a new file named Student.java.
2. In the Student.java file, add the following code:

package org.labex.entity;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

import java.util.Arrays;

@Component
@ConfigurationProperties(prefix = "student")
public class Student {
    private String id;
    private String name;
    private int age;
    private int[] courseId;

    @Override
    public String toString() {
        return "Student {id=" + id +
                ", name=" + name +
                ", age=" + age +
                ", course id=" + Arrays.toString(courseId) + "}";
    }

    // Getters and setters
    // ...
}

In this class, we use the @Component and @ConfigurationProperties annotations to automatically bind the properties from the application.yml file to the corresponding fields in the Student class.

Implement the StudentController

In this step, you will implement the StudentController to display the configured data.

1. Navigate to the org.labex.controller package and create a new file named StudentController.java.
2. In the StudentController.java file, add the following code:

package org.labex.controller;

import org.labex.entity.Student;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class StudentController {
    @Value("${school}")
    private String school;

    @Autowired
    private Student student;

    @GetMapping("/student")
    public String getStudent() {
        return "school=" + school + student.toString();
    }
}

In this controller, we use the @Value annotation to inject the school property, and the @Autowired annotation to inject the Student object. The getStudent() method will display the configured data on the browser when accessed via the /student endpoint.

Modify the Startup Class

In this step, you will modify the startup class to scan all classes in the org.labex package.

1. Navigate to the org.labex.springbootyaml package and open the DemoApplication.java file.
2. Update the DemoApplication class as follows:

package org.labex.springbootyaml;

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

@SpringBootApplication(scanBasePackages="org.labex")
public class DemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

By adding scanBasePackages="org.labex" to the @SpringBootApplication annotation, we ensure that all classes in the org.labex package are scanned and managed by the Spring context.

Package and Run the Application

In this final step, you will package the application into a JAR file and run the Spring Boot service.

1. Open a terminal and navigate to the root directory of your project using the following command:

cd ~/project/springbootyaml/

2. Run the following commands to package and start the Spring Boot service:

mvn clean package
mvn spring-boot:run

3. Once the service is running, open a web browser and navigate to http://localhost:8080/student. You should see the configured school and student information displayed on the page.

The output should look like this:

Congratulations! You have successfully completed the project by configuring the application using a YAML file, implementing the necessary classes, and running the Spring Boot service.

Summary

Congratulations! You have completed this project. You can practice more labs in LabEx to improve your skills.