org.springframework.web.servlet.resource

Class ResourceHttpRequestHandler

java.lang.Object

org.springframework.context.support.ApplicationObjectSupport

org.springframework.web.context.support.WebApplicationObjectSupport

org.springframework.web.servlet.support.WebContentGenerator

org.springframework.web.servlet.resource.ResourceHttpRequestHandler

All Implemented Interfaces:

Aware, InitializingBean, ApplicationContextAware, ServletContextAware, HttpRequestHandler

public class ResourceHttpRequestHandler
extends WebContentGenerator
implements HttpRequestHandler, InitializingBean

HttpRequestHandler that serves static resources optimized for superior browser performance (according to the guidelines of Page Speed, YSlow, etc.) by allowing for flexible cache settings ("cacheSeconds" property, last-modified support).

The "locations" property takes a list of Spring Resource locations from which static resources are allowed to be served by this handler. For a given request, the list of locations will be consulted in order for the presence of the requested resource, and the first found match will be written to the response, with Expires and Cache-Control headers set as configured. The handler also properly evaluates the Last-Modified header (if present) so that a 304 status code will be returned as appropriate, avoiding unnecessary overhead for resources that are already cached by the client. The use of Resource locations allows resource requests to easily be mapped to locations other than the web application root. For example, resources could be served from a classpath location such as "classpath:/META-INF/public-web-resources/", allowing convenient packaging and serving of resources such as a JavaScript library from within jar files.

To ensure that users with a primed browser cache get the latest changes to application-specific resources upon deployment of new versions of the application, it is recommended that a version string is used in the URL mapping pattern that selects this handler. Such patterns can be easily parameterized using Spring EL. See the reference manual for further examples of this approach.

For various front-end needs — such as ensuring that users with a primed browser cache get the latest changes, or serving variations of resources (e.g., minified versions) — ResourceResolvers can be configured.

This handler can be configured through use of a ResourceHandlerRegistry or the <mvc:resources/> XML configuration element.

Since:

3.0.4

Author:

Keith Donald, Jeremy Grelle, Juergen Hoeller

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private static class	ResourceHttpRequestHandler.ActivationMediaTypeFactory Inner class to avoid a hard-coded JAF dependency.

Field Summary

Fields

Modifier and Type	Field and Description
private static java.lang.String	CONTENT_ENCODING
private static boolean	jafPresent
private java.util.List<Resource>	locations
private static Log	logger
private java.util.List<ResourceResolver>	resourceResolvers
private java.util.List<ResourceTransformer>	resourceTransformers

Fields inherited from class org.springframework.web.servlet.support.WebContentGenerator

METHOD_GET, METHOD_HEAD, METHOD_POST

Constructor Summary

Constructors

Constructor and Description
ResourceHttpRequestHandler()

Method Summary

Modifier and Type	Method and Description
void	afterPropertiesSet() Invoked by a BeanFactory after it has set all bean properties supplied (and satisfied BeanFactoryAware and ApplicationContextAware).
java.util.List<Resource>	getLocations()
protected MediaType	getMediaType(Resource resource) Determine an appropriate media type for the given resource.
protected Resource	getResource(HttpServletRequest request)
java.util.List<ResourceResolver>	getResourceResolvers() Return the list of configured resource resolvers.
java.util.List<ResourceTransformer>	getResourceTransformers() Return the list of configured resource transformers.
void	handleRequest(HttpServletRequest request, HttpServletResponse response) Processes a resource request.
protected void	initAllowedLocations() Look for a PathResourceResolver among the resource resolvers and configure its "allowedLocations" to match the value of the locations property unless the "allowed locations" of the PathResourceResolver is non-empty.
protected boolean	isInvalidPath(java.lang.String path) Identifies invalid resource paths.
protected java.lang.String	processPath(java.lang.String path) Process the given resource path to be used.
protected void	setHeaders(HttpServletResponse response, Resource resource, MediaType mediaType) Set headers on the given servlet response.
void	setLocations(java.util.List<Resource> locations) Set a List of Resource paths to use as sources for serving static resources.
void	setResourceResolvers(java.util.List<ResourceResolver> resourceResolvers) Configure the list of ResourceResolvers to use.
void	setResourceTransformers(java.util.List<ResourceTransformer> resourceTransformers) Configure the list of ResourceTransformers to use.
java.lang.String	toString()
protected void	writeContent(HttpServletResponse response, Resource resource) Write the actual content out to the given servlet response, streaming the resource's content.

Methods inherited from class org.springframework.web.servlet.support.WebContentGenerator

applyCacheSeconds, applyCacheSeconds, cacheForSeconds, cacheForSeconds, checkAndPrepare, checkAndPrepare, getCacheSeconds, getSupportedMethods, isAlwaysMustRevalidate, isRequireSession, isUseCacheControlHeader, isUseCacheControlNoStore, isUseExpiresHeader, preventCaching, setAlwaysMustRevalidate, setCacheSeconds, setRequireSession, setSupportedMethods, setUseCacheControlHeader, setUseCacheControlNoStore, setUseExpiresHeader

Methods inherited from class org.springframework.web.context.support.WebApplicationObjectSupport

getServletContext, getTempDir, getWebApplicationContext, initApplicationContext, initServletContext, isContextRequired, setServletContext

Methods inherited from class org.springframework.context.support.ApplicationObjectSupport

getApplicationContext, getMessageSourceAccessor, initApplicationContext, requiredContextClass, setApplicationContext

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

CONTENT_ENCODING

private static final java.lang.String CONTENT_ENCODING

See Also:

Constant Field Values

logger

private static final Log logger

jafPresent

private static final boolean jafPresent

locations

private final java.util.List<Resource> locations

resourceResolvers

private final java.util.List<ResourceResolver> resourceResolvers

resourceTransformers

private final java.util.List<ResourceTransformer> resourceTransformers

Constructor Detail

ResourceHttpRequestHandler

public ResourceHttpRequestHandler()

Method Detail

setLocations

public void setLocations(java.util.List<Resource> locations)

Set a List of Resource paths to use as sources for serving static resources.

getLocations

public java.util.List<Resource> getLocations()

setResourceResolvers

public void setResourceResolvers(java.util.List<ResourceResolver> resourceResolvers)

Configure the list of ResourceResolvers to use.

By default PathResourceResolver is configured. If using this property, it is recommended to add PathResourceResolver as the last resolver.

getResourceResolvers

public java.util.List<ResourceResolver> getResourceResolvers()

Return the list of configured resource resolvers.

setResourceTransformers

public void setResourceTransformers(java.util.List<ResourceTransformer> resourceTransformers)

Configure the list of ResourceTransformers to use.

By default no transformers are configured for use.

getResourceTransformers

public java.util.List<ResourceTransformer> getResourceTransformers()

Return the list of configured resource transformers.

afterPropertiesSet

public void afterPropertiesSet()
                        throws java.lang.Exception

Description copied from interface: InitializingBean

Invoked by a BeanFactory after it has set all bean properties supplied (and satisfied BeanFactoryAware and ApplicationContextAware).

This method allows the bean instance to perform initialization only possible when all bean properties have been set and to throw an exception in the event of misconfiguration.

Specified by:

afterPropertiesSet in interface InitializingBean

Throws:

java.lang.Exception - in the event of misconfiguration (such as failure to set an essential property) or if initialization fails.

initAllowedLocations

protected void initAllowedLocations()

Look for a PathResourceResolver among the resource resolvers and configure its "allowedLocations" to match the value of the locations property unless the "allowed locations" of the PathResourceResolver is non-empty.

handleRequest

public void handleRequest(HttpServletRequest request,
                          HttpServletResponse response)
                   throws ServletException,
                          java.io.IOException

Processes a resource request.

Checks for the existence of the requested resource in the configured list of locations. If the resource does not exist, a 404 response will be returned to the client. If the resource exists, the request will be checked for the presence of the Last-Modified header, and its value will be compared against the last-modified timestamp of the given resource, returning a 304 status code if the Last-Modified value is greater. If the resource is newer than the Last-Modified value, or the header is not present, the content resource of the resource will be written to the response with caching headers set to expire one year in the future.

Specified by:

handleRequest in interface HttpRequestHandler

Parameters:

request - current HTTP request

response - current HTTP response

Throws:

ServletException - in case of general errors

java.io.IOException - in case of I/O errors

getResource

protected Resource getResource(HttpServletRequest request)
                        throws java.io.IOException

Throws:

java.io.IOException

processPath

protected java.lang.String processPath(java.lang.String path)

Process the given resource path to be used.

The default implementation replaces any combination of leading '/' and control characters (00-1F and 7F) with a single "/" or "". For example " // /// //// foo/bar" becomes "/foo/bar".

Since:

3.2.12

isInvalidPath

protected boolean isInvalidPath(java.lang.String path)

Identifies invalid resource paths. By default rejects:

• Paths that contain "WEB-INF" or "META-INF"
• Paths that contain "../" after a call to StringUtils.cleanPath(java.lang.String).
• Paths that represent a valid URL or would represent one after the leading slash is removed.

Note: this method assumes that leading, duplicate '/' or control characters (e.g. white space) have been trimmed so that the path starts predictably with a single '/' or does not have one.

Parameters:

path - the path to validate

Returns:

true if the path is invalid, false otherwise

getMediaType

protected MediaType getMediaType(Resource resource)

Determine an appropriate media type for the given resource.

Parameters:

resource - the resource to check

Returns:

the corresponding media type, or null if none found

setHeaders

protected void setHeaders(HttpServletResponse response,
                          Resource resource,
                          MediaType mediaType)
                   throws java.io.IOException

Set headers on the given servlet response. Called for GET requests as well as HEAD requests.

Parameters:

response - current servlet response

resource - the identified resource (never null)

mediaType - the resource's media type (never null)

Throws:

java.io.IOException - in case of errors while setting the headers

writeContent

protected void writeContent(HttpServletResponse response,
                            Resource resource)
                     throws java.io.IOException

Write the actual content out to the given servlet response, streaming the resource's content.

Parameters:

response - current servlet response

resource - the identified resource (never null)

Throws:

java.io.IOException - in case of errors while writing the content

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object