faucet-pipeline for Spring Boot
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Build Status Test coverage Quality Gate Maven Central

A Spring Boot starter and auto-configuration for the faucet-pipeline:

tl;dr: faucet-pipeline is a framework-independent, pluggable asset pipeline that takes the pain out of preprocessing JavaScript, CSS and associated files (e.g. images or fonts). It simplifies the process of converting modern JavaScript (ES6) to support older browsers (ES5), or Sass to CSS - eliminating typical low-level configuration nightmares.

The faucet-pipeline bundles your application files, fingerprints them and creates a manifest for them. It also can be used to watch the configured files and rerun the process during development.


This starter is needed when you want to use faucet with your Spring Boot project. The following issues have to be tackled:

  • The resource processed through the pipeline ("assets") should not be part of the regular Java / Groovy / Kotlin sources and other resources of the project. As such, the assets would be copied by the build system (either Maven or Gradle) itself. You have to provide a place for the assets, this is not something the starter can do for you.
  • The processed assets need to be in the class path of the Spring Application. This is also a build step, that the starter cannot do for you.

What the starter does however are the following tasks:

  • It checks whether a faucet-manifests exists (defaults to classpath:/manifest.json) and if so, loads it
  • It checks whether the application is either a servlet or reactive web application. If not, the starter does nothing.
  • For a web application it registers a ResourceResolver that is able to retrieve internal urls that might are the output of finger printing and map them to external urls.

This works for servlet and reactive Spring applications.


git clone https://github.com/michael-simons/faucet-pipeline-spring-boot-starter
cd faucet-pipeline-spring-boot-starter
./mvnw clean install
cd demo-webmvc
FAUCETPIPELINE_CACHEMANIFEST=false ./mvnw spring-boot:run

Goto localhost:8080.

Usage and configuration


Just include the starter in your pom.xml:


The starter can only work if Springs resource chain is active. The starter won't activate this for you, so please configure


The resource resolver will be mapped to /**, so basically that's it.

Compile time

Make sure that your assets end up into /classes. This project contains two demos, demo-webmvc and demo-webflux. The following approach is from demo-webmvc.

Configure your faucet-pipeline

Follow the instructions from the website:

npm init # gets you a fresh package.json
npm install --save\ # Installs the pipeline for you

In your package.json add the following scripts:

"scripts": {
    "compile": "faucet --fingerprint --compact",
    "watch": "faucet --no-fingerprint --watch"

The compact-switch is optional.

Create a faucet.config.js next to package.json. Here's the one from `demo-webmvc``

let targetBaseDir = "./target/classes/static"
const path = require('path');

module.exports = {
    js: [{
        source: "./src/main/assets/javascripts/application.js",
        target: targetBaseDir + "/javascripts/application.js"
    sass: [{
        source: "./src/main/assets/stylesheets/application.scss",
        target: targetBaseDir + "/stylesheets/application.css"
    static: [{
        source: "./src/main/assets/images",
        target: targetBaseDir + "/images"
    manifest: {
        target: "./target/classes/manifest.json",
        key: 'short',
        webRoot: targetBaseDir

You'll notice that it puts the all processed assets into ./target/classes/static. That is where Spring Boot looks for static files by default. Pushing it directly into the classes folder allows dynamic reloading later on. An alternative would be going through generated-resources.

As the above configuration writes the assets into subdirectories, you have to configure your Spring application to include those path patterns:

faucet-pipeline.path-patterns = /javascripts/**, /stylesheets/**, /images/**

Add frontend-maven-plugin

frontend-maven-plugin is "Maven-node-grunt-gulp-npm-node-plugin to end all maven-node-grunt-gulp-npm-plugins.":

With the package.json and faucet-configuration in place, add the following configuration:

                <arguments>run compile --fingerprint</arguments>

This downloads Node and NPM and installs all dependencies via package.json and executes the pipeline during build. Assuming that your Spring Boot application has the Spring Boot Maven plugin configured like so


you can run the application with mvn spring-boot:run. When you use a supported template language like Thymeleaf and the URL-helper they offer, links to assets will contain the finger printed resources automatically. Those links

<link th:href="@{/stylesheets/application.css}" rel="stylesheet" data-turbolinks-track="reload">
<script th:src="@{/javascripts/application.js}" data-turbolinks-track="reload"></script>

Will be turned into

<link href="/stylesheets/stylesheets/application-70d5f3dc18d122548efadcedfc0874f0.css" rel="stylesheet" data-turbolinks-track="reload">
<script src="/javascripts/javascripts/application-8af210bcc164a457cb381a627729320b.js" data-turbolinks-track="reload"></script>

Automatic restart, manifest caching

Use spring-boot-devtools to automatically reload the application when things change:


The manifest is cached by default but that can be turned off via faucet-pipeline.cache-manifest = false. One easy way to do this without hardcoding it into a properties file is as an environment variable:

Run the demo in one window like so:

FAUCETPIPELINE_CACHEMANIFEST=false ./mvnw spring-boot:run

And in another terminal

npm run watch

And you'll see the assets being processed and refreshed in the app.

About the demo application

Both demos - for WebMVC and Webflux - collect ideas. They use Turbolinks for quick navigation between server side rendered sites. Turbolinks come from Ruby on Rails.

The demo is a Bootstrap-based site branded with the INNOQ-theme and it looks like this:

Homepage WebMVC demo

Going reactive

The demo-webflux Version is a fully reactive, Spring 5 + Kotlin based application. Please start this one directly as JAR, the Maven Spring Boot Plugin seems to configure stuff slightly differently.