Static Resources

This option provides a convenient way to serve static resources from a list of Resource-based locations.

In the next example, given a request that starts with /resources, the relative path is used to find and serve static resources relative to /public under the web application root or on the classpath under /static. The resources are served with a one-year future expiration to ensure maximum use of the browser cache and a reduction in HTTP requests made by the browser. The Last-Modified information is deduced from Resource#lastModified so that HTTP conditional requests are supported with "Last-Modified" headers.

The following listing shows how to do so:

Java
Kotlin
Xml

@Configuration
public class WebConfiguration implements WebMvcConfigurer {

	@Override
	public void addResourceHandlers(ResourceHandlerRegistry registry) {
		registry.addResourceHandler("/resources/**")
				.addResourceLocations("/public", "classpath:/static/")
				.setCacheControl(CacheControl.maxAge(Duration.ofDays(365)));
	}
}

@Configuration
class WebConfiguration : WebMvcConfigurer {

	override fun addResourceHandlers(registry: ResourceHandlerRegistry) {
		registry.addResourceHandler("/resources/**")
			.addResourceLocations("/public", "classpath:/static/")
			.setCacheControl(CacheControl.maxAge(Duration.ofDays(365)))
	}
}

<mvc:resources mapping="/resources/**" location="/public, classpath:/static/"
			   cache-period="31556926" />

The resource handler also supports a chain of ResourceResolver implementations and ResourceTransformer implementations, which you can use to create a toolchain for working with optimized resources.

You can use the VersionResourceResolver for versioned resource URLs based on an MD5 hash computed from the content, a fixed application version, or other. A ContentVersionStrategy (MD5 hash) is a good choice — with some notable exceptions, such as JavaScript resources used with a module loader.

The following example shows how to use VersionResourceResolver:

Java
Kotlin
Xml

@Configuration
public class VersionedConfiguration implements WebMvcConfigurer {

	@Override
	public void addResourceHandlers(ResourceHandlerRegistry registry) {
		registry.addResourceHandler("/resources/**")
				.addResourceLocations("/public/")
				.resourceChain(true)
				.addResolver(new VersionResourceResolver().addContentVersionStrategy("/**"));
	}
}

@Configuration
class VersionedConfiguration : WebMvcConfigurer {

	override fun addResourceHandlers(registry: ResourceHandlerRegistry) {
		registry.addResourceHandler("/resources/**")
			.addResourceLocations("/public/")
			.resourceChain(true)
			.addResolver(VersionResourceResolver().addContentVersionStrategy("/**"))
	}
}

<mvc:resources mapping="/resources/**" location="/public/">
	<mvc:resource-chain resource-cache="true">
		<mvc:resolvers>
			<mvc:version-resolver>
				<mvc:content-version-strategy patterns="/**"/>
			</mvc:version-resolver>
		</mvc:resolvers>
	</mvc:resource-chain>
</mvc:resources>

You can then use ResourceUrlProvider to rewrite URLs and apply the full chain of resolvers and transformers — for example, to insert versions. The MVC configuration provides a ResourceUrlProvider bean so that it can be injected into others. You can also make the rewrite transparent with the ResourceUrlEncodingFilter for Thymeleaf, JSPs, FreeMarker, and others with URL tags that rely on HttpServletResponse#encodeURL.

Note that, when using both EncodedResourceResolver (for example, for serving gzipped or brotli-encoded resources) and VersionResourceResolver, you must register them in this order. That ensures content-based versions are always computed reliably, based on the unencoded file.

For WebJars, versioned URLs like /webjars/jquery/1.2.0/jquery.min.js are the recommended and most efficient way to use them. The related resource location is configured out of the box with Spring Boot (or can be configured manually via ResourceHandlerRegistry) and does not require to add the org.webjars:webjars-locator-core dependency.

Version-less URLs like /webjars/jquery/jquery.min.js are supported through the WebJarsResourceResolver which is automatically registered when the org.webjars:webjars-locator-core library is present on the classpath, at the cost of a classpath scanning that could slow down application startup. The resolver can re-write URLs to include the version of the jar and can also match against incoming URLs without versions — for example, from /webjars/jquery/jquery.min.js to /webjars/jquery/1.2.0/jquery.min.js.

The Java configuration based on ResourceHandlerRegistry provides further options for fine-grained control, for example, last-modified behavior and optimized resource resolution.