WebJars in Spring MVC

Last week I announced the WebJars project that allows you to specify your web libraries (JavaScript, CSS, etc) as dependencies in your Java web applications. With some help from Jeremy Grelle I was able to get a simple WebJars Spring MVC example working.

First you will need to add the WebJars repository to your build. For Maven, just add the following to your “pom.xml” build file:

    <repositories>
        <repository>
            <id>webjars</id>
            <url>http://webjars.github.com/m2</url>
        </repository>
    </repositories>

Then add a WebJar dependency, like Twitter Bootstrap:

        <dependency>
            <groupId>com.github.twitter</groupId>
            <artifactId>bootstrap</artifactId>
            <version>2.0.2</version>
        </dependency>

Then you need to add a resource handler to Spring MVC that maps requests from a given path to files in the classpath. The WebJars are all inside of a “public” directory. If you are using Java configuration in Spring then you would do the following:

@Configuration
@EnableWebMvc
public class WebConfig extends WebMvcConfigurerAdapter {
 
  @Override
  public void addResourceHandlers(ResourceHandlerRegistry registry) {
    registry.addResourceHandler("/public/**").addResourceLocations("classpath:/public/");
  }
}

Or if you are using XML config then add the following to your Spring config:

<mvc:resources mapping="/public/**" location="classpath:/public/"/>

Then you can reference a WebJar’s assets with something like:

<link rel='stylesheet' media='screen' href='/public/stylesheets/bootstrap.min.css'>

How easy is that? Now you are managing your web libraries as versioned dependencies and you even get transitive dependencies! Check out the full source code for this example on GitHub: https://github.com/jamesward/spring_webjars_demo

Right now there are only a couple of WebJars so if you need something else then simply request a new one via a new issue on GitHub.

Please let me know what you think about this. Thanks!