Spring Boot: Restarting App using Dev Tools with IntelliJ IDEA

Spring Boot provides spring-boot-devtools module that allows the app to “smartly” restart whenever the files on the classpath have changed.

Because the rarely changed classes (ex: 3rd party JARs) are separated out into a different classloader from the app’s actively developed classes’ classloader, it allows Spring Boot to quickly restart the app compared to “cold start”.

DEPENDENCY

First, add the following dependency:-

<dependency>
	<groupid>org.springframework.boot</groupid>
	<artifactid>spring-boot-devtools</artifactid>
	<scope>runtime</scope>
</dependency>

CONFIGURING INTELLIJ IDEA

In IntelliJ IDEA:-

• Click SHIFT twice to bring up the “Search History” dialog.
• Select “Actions” tab.
• Type “Registry” in the search box.
• Select “Registry…”.

In the “Registry” dialog:-

• Find “compiler.automake.allow.when.app.running” key.
• Check the checkbox.
• Close the dialog.

In IntelliJ IDEA “Preferences” dialog:-

• Go to “Build, Execution, Deployment” » “Compiler”.
• Check “Build project automatically”.
• Close the dialog.

Finally, instead of running Maven goals to run the Spring Boot app, select the Application class (annotated with @SpringBootApplication) and run it from IntelliJ IDEA.

Anytime the app’s class files have changed, IntelliJ IDEA will compile the app, which will then trigger Spring Boot Dev Tools to restart the app.