SpringBoot DevTools : Automatic Restart with Live Reload!

Many may not know about this feature even with 10+ years of exp in this industry. Let’s explore.

Photo by Ash Amplifies on Unsplash

While many developers use hot reloading tools, Spring Boot DevTools introduces a surprising twist: automatic restart.

It not only reloads your changes without a full application restart but also isolates class loaders for faster reloads.

DevTools tracks only your application code (not third-party libraries), so when you make a change in your codebase, it reloads only that, keeping the rest of the application intact.

Additionally, DevTools supports LiveReload integration, allowing your browser to automatically refresh whenever you make a change to your front-end code (HTML, CSS, JS), giving an instant preview without manually hitting refresh.

It’s a seamless development experience that drastically improves productivity, combining both backend and frontend reloading effortlessly.

How Can We Implement this?

1. Add Spring Boot DevTools Dependency

First, add the spring-boot-devtools dependency to your pom.xml (for Maven) .

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-devtools</artifactId>
    <optional>true</optional>
</dependency>

2. Enable Automatic Restart (default)

After adding the DevTools dependency, automatic restart is enabled by default in the development environment. Spring Boot will automatically detect any code changes (e.g., in controllers or services) and restart only the modified parts of your application, without a full restart.

3. Enable LiveReload for Frontend Changes

Spring Boot DevTools also comes with LiveReload functionality, which automatically refreshes the browser when you change static resources (like HTML, CSS, and JS files). This feature is also enabled by default.

To use LiveReload:

• Ensure the LiveReload browser extension is installed (optional).
• You can find extensions for Chrome or Firefox, but most modern browsers support LiveReload natively.

Once you run the application and make changes to your static resources (HTML, JS, CSS), the browser will automatically refresh.

4. Running in Development Mode

To ensure that DevTools doesn’t get bundled with production builds, it is automatically disabled when running a fully packaged application (e.g., with java -jar). However, it remains active when running in development mode using:

mvn spring-boot:run

5. DevTools Settings (Optional)

You can customize DevTools by adding properties in your application.properties or application.yml.

For example:

#Properties file 

# Enable or disable LiveReload (enabled by default)
spring.devtools.livereload.enabled=true
# Disable restart feature (enabled by default)
spring.devtools.restart.enabled=true

6. Auto-Restart Trigger

The automatic restart is triggered when you change files under the src/main/java or src/main/resources directories. However, files in the src/main/resources/META-INF directory or configuration files like application.yml also trigger the restart.

That’s it! With Spring Boot DevTools, both automatic restart and live reload will now work seamlessly, making your development process faster and more efficient.

Hope this helps!!