Custom theme for a Vaadin & Spring-boot application

Recently I wrote an application based on Vaadin Spring-boot, and when I needed to modify the theme of the application I needed to do some research as how to achieve that. I think that at the time the combination of Vaadin and Spring-boot is still pretty new so that information still must be sought. So in this post I describe the necessary steps.

I use the following versions of different tools:

  • Oracle JDK 1.8.0_45
  • vaadin 7.4.5
  • vaadin-spring-start 1.0.0.beta3
  • spring-boot 1.2.3.RELEASE
  • spring 4.1.6.RELEASE

My IDE is IntelliJ IDEA 14.1.3

Creating the basic application

I create the application project (named vsbt for vaadin spring boot theme) by using the Spring Initializr from within IDEA, but it can be done via the Website as well:


For this demo I set up a project with the following properties that has only Vaadin as a dependency:



After finishing the setup I have an IDEA maven project with the basic application class, but still with no UI:


So to have something visible, I add a MainUI class which uses the valo theme and which just inserts a button in the UI. The button is nonfunctional, as this demo is only concerning with theming the UI and not with functionality:

 * Copyright (c) 2015 sothawo
package org.sothawo.vsbt;

import com.vaadin.annotations.Theme;
import com.vaadin.server.VaadinRequest;
import com.vaadin.spring.annotation.SpringUI;
import com.vaadin.ui.Button;
import com.vaadin.ui.UI;
import com.vaadin.ui.VerticalLayout;

 * @author P.J. Meisch (
public class MainUI extends UI {
    protected void init(VaadinRequest vaadinRequest) {
        VerticalLayout layout = new VerticalLayout();

        layout.addComponent(new Button("This is a button"));


Compiling and running the application gives the following result in the browser:


Changing the theme

Now for changing the theme. I want to create a theme named colored where I change some colors. The first step ist to put the theme files (sass files) in the src/main/webapp/VAADIN/themes/colored folder:


The styles.scss file:

@import "addons.scss";
@import "colored.scss";

The colored.scss file:

@import "../valo/valo.scss";

@mixin colored {
  @include valo;

  .v-app {
    background-color: red;

  .v-button {
    background-image: none;
    background-color: yellow;

@include colored;

I don’t get into the details of sass files here. In the MainUI class the annotation for the theme must be changed to @Theme("colored").

When I now start the program after building the program with the following command:

mvn clean package
cd target
java -jar vsbt-0.0.1-SNAPSHOT.jar

then the browser shows no theme:


The reason for this is that the files that are located under the src/main/webapp directory are not considered when the jar is packaged, this is only done when building a war file. So the first step that needs to be done is to specify this directory as a resource directory in the maven pom.xml:


One might be tempted to move the VAADIN/themes/colored folder to src/main/resources, but there is still a problem to be solved. When building and running the application, the logging output shows an error message like:

Jun 02, 2015 9:21:14 PM com.vaadin.server.VaadinServlet persistCacheEntry
WARNUNG: Error persisting scss cache /private/var/folders/xw/1zt9sly53_76h29g7067_y700000gp/T/tomcat-docbase.6378846904000133878.8080/VAADIN/themes/colored/styles.scss.cache /private/var/folders/xw/1zt9sly53_76h29g7067_y700000gp/T/tomcat-docbase.6378846904000133878.8080/VAADIN/themes/colored/styles.scss.cache (No such file or directory)
        at Method)

This happens because the sass compiler – at least on my Mac – has problems with persisting the compiled css file. To remove that error it is necessary to add the sass compiler to the compile step in the maven pom.xml (and this is the reason to leave the files in the src/main/webapp directory, it’s there that the compiler searches for them):


When now compiling the project, the addons.scss and the colored.css files are created in the theme directory and packaged in the application, and after packaging and running, the browser shows the following application with no more logged errors:


I hope this post can help if somebody needs to theme a vaadin spring-boot application and has the same problems finding out where to put the files and how to compile them.