org.apache.shindig.gadgets.rewrite

Class CacheEnforcementVisitor

java.lang.Object

org.apache.shindig.gadgets.rewrite.ResourceMutateVisitor

org.apache.shindig.gadgets.rewrite.CacheEnforcementVisitor

All Implemented Interfaces:

DomWalker.Visitor

public class CacheEnforcementVisitor
extends ResourceMutateVisitor

Visitor that walks over html tags as specified by resourceTags and reserves html tag nodes whose uri attributes are either not in cache, or are in cache, but the response in cache is either stale or an error response. In all the above mentioned cases except for the error case, we trigger a background fetch for the resource. This visitor should be used by a rewriter in conjuction with other visitors which depend on the uri of the html node being in cache. Note that in order to use the CacheEnforcementVisitor effectively, the shindig property shindig.cache.http.strict-no-cache-resource.max-age should be set to a positive value, so that strict no-cache resources are stored in cache with this ttl, and unnecessary fetches are not triggered each time for such resources.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.shindig.gadgets.rewrite.ResourceMutateVisitor

ResourceMutateVisitor.Tags

Nested classes/interfaces inherited from interface org.apache.shindig.gadgets.rewrite.DomWalker.Visitor

DomWalker.Visitor.VisitStatus

Field Summary

Fields

Modifier and Type	Field and Description
static String	CACHE_ENFORCEMENT_FETCH_PARAM

Fields inherited from class org.apache.shindig.gadgets.rewrite.ResourceMutateVisitor

featureConfig, resourceTags

Constructor Summary

Constructors

Constructor and Description
CacheEnforcementVisitor(ContentRewriterFeature.Config featureConfig, Executor executor, HttpCache cache, RequestPipeline requestPipeline, ResourceMutateVisitor.Tags... resourceTags) Constructs the cache enforcement visitor.

Method Summary

Methods

Modifier and Type	Method and Description
protected HttpRequest	createNewHttpRequest(Gadget gadget, String uriStr) Constructs a new HttpRequest in the context of the gadget.
protected DomWalker.Visitor.VisitStatus	handleResponseInCache(HttpRequest request, HttpResponse response) The action to be performed if the response is in cache.
protected DomWalker.Visitor.VisitStatus	handleResponseNotInCache(HttpRequest request) The action to be performed if the response is not in cache.
protected Collection<Pair<Node,Uri>>	mutateUris(Gadget gadget, Collection<Node> nodes)
protected void	triggerFetch(HttpRequest request) Triggers a background fetch for a resource.
DomWalker.Visitor.VisitStatus	visit(Gadget gadget, Node node) Visit a particular Node in the DOM.

Methods inherited from class org.apache.shindig.gadgets.rewrite.ResourceMutateVisitor

revisit

Methods inherited from class java.lang.Object

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

Field Detail

CACHE_ENFORCEMENT_FETCH_PARAM

public static final String CACHE_ENFORCEMENT_FETCH_PARAM

See Also:

Constant Field Values

Constructor Detail

CacheEnforcementVisitor

public CacheEnforcementVisitor(ContentRewriterFeature.Config featureConfig,
                       Executor executor,
                       HttpCache cache,
                       RequestPipeline requestPipeline,
                       ResourceMutateVisitor.Tags... resourceTags)

Constructs the cache enforcement visitor.

Method Detail

createNewHttpRequest

protected HttpRequest createNewHttpRequest(Gadget gadget,
                               String uriStr)

Constructs a new HttpRequest in the context of the gadget. For example, the implementation may choose to copy User Agent or referer etc.

visit

public DomWalker.Visitor.VisitStatus visit(Gadget gadget,
                                  Node node)
                                    throws RewritingException

Description copied from class: ResourceMutateVisitor

Visit a particular Node in the DOM.

Specified by:

visit in interface DomWalker.Visitor

Overrides:

visit in class ResourceMutateVisitor

Parameters:

gadget - Context for the request.

node - Node being visited.

Returns:

Status, see VisitStatus

Throws:

RewritingException

handleResponseInCache

protected DomWalker.Visitor.VisitStatus handleResponseInCache(HttpRequest request,
                                                  HttpResponse response)

The action to be performed if the response is in cache.

Parameters:

request - HttpRequest to fetch the resource of the node.

response - The HttpResponse retrieved from cache.

Returns:

The visit status of the node.

handleResponseNotInCache

protected DomWalker.Visitor.VisitStatus handleResponseNotInCache(HttpRequest request)

The action to be performed if the response is not in cache.

Parameters:

request - HttpRequest to fetch the resource of the node.

Returns:

The visit status of the node.

triggerFetch

protected void triggerFetch(HttpRequest request)

Triggers a background fetch for a resource.

Parameters:

request - HttpRequest to fetch the resource of the node.

mutateUris

protected Collection<Pair<Node,Uri>> mutateUris(Gadget gadget,
                                    Collection<Node> nodes)

Specified by:

mutateUris in class ResourceMutateVisitor