Wouter Wouter - 17 days ago 9
Java Question

Spring boot devtools - Static content reloading does not work in IntelliJ

When building my first Spring Boot app, I discovered that I need to restart my app every time I make a change to a Javascript file in /resources/static/some-file.js

This is very time consuming.

When I move the files to the /webapps/ folder, it works as expected, but the files are not packaged in a JAR. The docs mention this, so I cannot continue this way.

I read all about

spring-boot-devtools
, and have installed it in my POM, but the hotswapping doesn't seam to be working. I still need to restart the entire app to see a Javascript or CSS file change.

When the app starts, I can see the line
LiveReload server is running on port 35729
, so
spring-boot-devtools
must be doing something...

What would be the steps to further investigate what is going wrong?

My guess is that when IntelliJ runs the app, the files are copied, so when I make a change, I'm actually changing the original files and not the ones used by the running app.

PS: I'm using Maven, IntelliJ IDEA 15 and Spring Boot 1.3.3 with the embedded Tomcat server. I'm not sure what command IntelliJ runs to start the app. The IDE is handling this "automatically". Perhaps I need to change my run configuration?

Answer

You need to turn on a couple of features in IntelliJ to make this work.

First, there's a project specific setting which you would need to apply on any project you want to use devtools in. Go to Preferences > Compiler and enable "Make project automatically."

The next setting is an IDEA registry setting that applies to all projects.

  • In OSX, press Shift+Command+A (Shift+Ctrl+A in Windows)
  • Type "Registry" in the search box that appears, and select the registry to open it.
  • Lookup compiler.automake.allow.when.app.running and enable it.

After that, restart your app. You will notice that the project keeps rebuilding with every change you make. When you check out the result in the browser, you will see both static files and code have been updated.

I also wrote a blog post about this a little while ago. http://patrickgrimard.com/2016/01/18/spring-boot-devtools-first-look/