[[mvc-config-static-resources]]
= Static Resources

[.small]#xref:web/webflux/config.adoc#webflux-config-static-resources[See equivalent in the Reactive stack]#

This option provides a convenient way to serve static resources from a list of
{spring-framework-api}/core/io/Resource.html[`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 with Java configuration:

[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim",role="primary"]
----
	@Configuration
	@EnableWebMvc
	public class WebConfig implements WebMvcConfigurer {

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

Kotlin::
+
[source,kotlin,indent=0,subs="verbatim",role="secondary"]
----
	@Configuration
	@EnableWebMvc
	class WebConfig : WebMvcConfigurer {

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

The following example shows how to achieve the same configuration in XML:

[source,xml,indent=0,subs="verbatim,quotes"]
----
	<mvc:resources mapping="/resources/**"
		location="/public, classpath:/static/"
		cache-period="31556926" />
----

See also
xref:web/webmvc/mvc-caching.adoc#mvc-caching-static-resources[HTTP caching support for static resources].

The resource handler also supports a chain of
{spring-framework-api}/web/servlet/resource/ResourceResolver.html[`ResourceResolver`] implementations and
{spring-framework-api}/web/servlet/resource/ResourceTransformer.html[`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` in Java configuration:

[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim",role="primary"]
----
	@Configuration
	@EnableWebMvc
	public class WebConfig implements WebMvcConfigurer {

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

Kotlin::
+
[source,kotlin,indent=0,subs="verbatim",role="secondary"]
----
	@Configuration
	@EnableWebMvc
	class WebConfig : WebMvcConfigurer {

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

The following example shows how to achieve the same configuration in XML:

[source,xml,indent=0,subs="verbatim"]
----
<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 https://www.webjars.org/documentation[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`.

TIP: The Java configuration based on `ResourceHandlerRegistry` provides further options
for fine-grained control, e.g. last-modified behavior and optimized resource resolution.



