Spring Boot DevTools is designed to improve developer productivity by reducing restart time and enabling rapid feedback during development.

This post explains what DevTools is, how it works, and how to use it effectively without surprises.

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1. What Is Spring Boot DevTools?

Spring Boot DevTools is a set of development-time tools that provide:

• Automatic application restart
• Hot reload of resources
• LiveReload browser refresh
• Sensible development defaults

It is only active in development and disabled automatically in production.

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2. Adding DevTools to Your Project

Add the dependency to your build tool.

Maven

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-devtools</artifactId>
    <scope>runtime</scope>
</dependency>

Gradle

dependencies {
    developmentOnly 'org.springframework.boot:spring-boot-devtools'
}

Once added, no extra configuration is required.

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3. Automatic Restart (Core Feature)

DevTools monitors classpath changes and restarts the application automatically.

How it works:

• Detects class changes
• Restarts only the application context
• Keeps JVM running

This is much faster than a full restart.

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4. Classpath Splitting (Why Restart Is Fast)

DevTools uses two classloaders:

• Base classloader → third-party libraries (unchanged)
• Restart classloader → application classes (changes frequently)

Only the restart classloader is refreshed.

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5. LiveReload Support

DevTools supports LiveReload, which automatically refreshes the browser when resources change.

Supported resources:

• HTML
• CSS
• JavaScript
• Thymeleaf templates

To use it:

• Enable LiveReload in your browser
• DevTools triggers refresh automatically

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6. Disabling Restart (When Needed)

You can disable restart if required.

spring.devtools.restart.enabled=false

Useful when:

• Debugging complex issues
• Running background tasks
• Using custom classloaders

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7. Excluding Paths from Restart

Exclude files that shouldn’t trigger restart:

spring.devtools.restart.exclude=static/**,public/**

This prevents unnecessary restarts.

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8. DevTools & IDE Configuration

For best experience:

• Enable Build Automatically (IntelliJ)
• Enable Auto-make while app running
• Use HotSwap for method changes

IDE configuration greatly affects DevTools behavior.

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9. DevTools in Production

DevTools is:

• Automatically disabled in production
• Not included in repackaged JARs by default

Never rely on DevTools behavior in production environments.

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10. Common Pitfalls

• Expecting hot reload for all changes
• Confusing restart with HotSwap
• Using DevTools in production
• Restart loops due to file watchers

Understanding limitations avoids frustration.

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11. Best Practices

• Use DevTools only in development
• Combine with IDE HotSwap
• Exclude unnecessary paths
• Restart manually if behavior seems inconsistent
• Keep DevTools dependency out of production builds

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12. Summary

• DevTools improves development speed
• Automatic restart is its core feature
• LiveReload refreshes browser automatically
• Classloader split makes restart fast
• Safe and disabled in production

Spring Boot DevTools is a must-have for efficient development.

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What's Next?

Next post:

36 - Using Spring Boot Actuator (Health, Metrics, Insights)

We’ll explore monitoring and production insights using Actuator.