Master Spring Boot DevTools: Complete Guide to Hot Reload Configuration

Quick Configuration Steps

Add Dependency : Include the DevTools starter in

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

to keep it out of production builds.

Maven Plugin Configuration : Set <fork>true</fork> inside the spring-boot-maven-plugin so DevTools can trigger a restart.

Enable Automatic Compilation in IDEA : Navigate to Build, Execution, Deployment → Compiler and check Build project automatically .

Allow Runtime Compilation : Open IDEA Registry (Ctrl+Shift+Alt+/ or Cmd+Shift+Option+/) and enable compiler.automake.allow.when.app.running. The location may vary by version (Advanced Settings).

Configure Application Properties : Add restart, exclude paths, additional monitoring paths, and cache settings in application.yml or application.properties as shown below.

Restart IDEA : After all changes, restart the IDE to avoid cached configuration issues.

Application Property Examples

spring:
  devtools:
    restart:
      enabled: true   # enable hot reload (default true)
      exclude: "static/**,public/**"   # paths that do not trigger restart
      additional-paths: src/main/java   # extra monitored paths
    livereload:
      enabled: true   # enable browser LiveReload
  freemarker:
    cache: false   # disable template engine cache

spring.devtools.restart.enabled=true
spring.devtools.restart.exclude=static/**,public/**
spring.devtools.restart.additional-paths=src/main/java
spring.freemarker.cache=false
spring.thymeleaf.cache=false

Usage Caveats and Limitations

Effective Scope : Only changes inside method bodies trigger a restart; changes to class signatures, fields, or bean definitions require a full restart.

Session Loss : DevTools restarts the entire application, which clears HTTP sessions.

Production Disable : When the application is packaged (java -jar), DevTools is automatically disabled, but it is safer to mark the dependency as <optional>true</optional>.

Static Resource Optimization : Modifications in /static, /public, or /templates only trigger a browser refresh, not an application restart.

Manual Save Trigger : Although IDEA auto‑saves, you may need to press Ctrl+S or Ctrl+F9 (Build Project) to ensure compilation.

Verification Steps

Run the Spring Boot application in Debug mode .

Modify a controller’s return value and save the file.

Observe the console logs to confirm a fast restart.

Refresh the browser to verify that the changes are reflected.

Alternative Solutions

JRebel : Commercial tool that supports hot swapping of class structure without restart, offering a smoother development experience.

HotSwapAgent : Open‑source solution that leverages JVM HotSwap to achieve limited class‑structure hot replacement.

Conclusion

Spring Boot DevTools is designed as a development‑time tool that provides rapid restarts and static‑resource refreshes, making everyday debugging faster. For more advanced hot‑deployment needs, consider integrating JRebel or container‑based hot‑swap mechanisms.