application.yml alternative in Spring Boot

Introduction

Sometimes you want to configure your Spring Boot app using a different file format than application.yml. This helps when you prefer simpler or more familiar formats.

You want to use <code>application.properties</code> instead of YAML for easier editing.

You need to override settings in environment variables for cloud deployment.

You want to use command line arguments to quickly change config without files.

You prefer JSON format for configuration in some cases.

You want to externalize config in a custom file for different environments.

Syntax

Spring Boot

spring.application.name=MyApp
server.port=8080
logging.level.root=INFO

application.properties uses key=value pairs, one per line.

Keys use dot notation to represent nested properties.

Examples

Basic properties file with app name and port.

Spring Boot

spring.application.name=MyApp
server.port=8080

Set logging level for Spring framework to DEBUG.

Spring Boot

logging.level.org.springframework=DEBUG

Database connection settings in properties format.

Spring Boot

spring.datasource.url=jdbc:mysql://localhost:3306/mydb
spring.datasource.username=root
spring.datasource.password=secret

Sample Program

This Spring Boot app reads the app name from application.properties and shows it on the home page.

Spring Boot

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

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

@RestController
class HelloController {

    @Value("${spring.application.name}")
    private String appName;

    @GetMapping("/")
    public String home() {
        return "Welcome to " + appName + "!";
    }
}

Important Notes

You can use application.properties as a simple alternative to application.yml.

Environment variables and command line args can also override these settings.

YAML supports complex structures better, but properties files are easier for simple configs.

Summary

application.properties is a common alternative to application.yml.

It uses simple key=value lines for configuration.

You can choose the format that fits your project and team best.