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Class w3c.www.protocol.http.cache.CacheFilter

java.lang.Object
   |
   +----w3c.www.protocol.http.cache.CacheFilter

public class CacheFilter

extends Object

implements PropRequestFilter, PropertyMonitoring

CACHE_CONNECTED_P

Name of the property indicating wether the cache is connected or not.

CACHE_DIRECTORY_P

Name of the property giving the cache's directory.

CACHE_SIZE_P

The name of the properties indicating the size of the cache (in bytes).

CACHEDIR_SPLITS

Number of sub-levels file system directories in the cache directory.

connected

Is this cache connected ?

debug

The debug flag.

DEBUG_P

Name of the property indicating if the cache is in debug mode.

directory

The directory where the cache is stored.

expires_drift

The expires drift.

FILE_SIZE_RATIO_P

Name of the property indicating the max size for files to be cached.

fileSizeRatio

The file size quota.

GARBAGE_COLLECTION_ENABLED_P

Name of the property enabling garbage collection of the cache.

garbageCollectionEnabled

Should we enable garbage collection of the cache ?

HOW_HIT

STATE_HOW value - Indicates request fulfilled through a hot.

HOW_MISS

STATE_HOW value - Indicates request fulfilled through a miss.

HOW_REVALIDATION_FAILURE

STATE_HOW value - indicates request fulfilled through unsucessfull revalidation.

HOW_REVALIDATION_SUCCESS

STATE_HOW value - indicates request fulfilled through sucessfull revalidation.

props

The properties we initialized ourself from.

shared

Is this cached shared ?

SHARED_P

Name of the property indicating if this cache is shared.

size

The current cache size.

STATE_CACHABLE

Name of the property that indicates that the cache cab be used.

STATE_HOW

Logging state - for some logger to keep track of what's happening.

STATE_NOCACHE

The state used to disable that filter per request.

STATE_ORIGREQ

Name of the request state used tokeep track of original request

STATE_RESOURCE

STATE_REVALIDATION

Name of the request state that marks a request as being a revalidation.

STATE_WARNINGS

Name of the request state used to collect warnings.

stats

Our real time statistics.

WARN_DISCONNECTED

The HTTP warning used to notify of a disconnected cache.

WARN_HEURISTIC

The HTTP warning used to indicate a heuristic expiration time.

WARN_STALE

The HTTP warning used to mark invalid entries

CacheFilter()

addWarning(Request, HttpWarning)

Add a warning, to be emitted at reply time.

canCache(Request, Reply)

Can the given reply to the given request be added to the cache.

canUseCache(Request)

Can the given request be fullfilled by the cache filter ? This method distinguishes two situations.

checkCacheDirectory(File)

exceptionFilter(Request, HttpException)

This filter doesn't handle exceptions.

getCacheSize()

Get the total size allocated to the cache.

getFile(URL)

Get a file to save that URL in.

getHow(Request)

Returns a String indicating what the cache did with that request.

getStatistics()

Get the statistics repository associated with that filter.

getSubdirectory(int)

hasResource(String)

Does the cache knows about this resource ?

ingoingFilter(Request)

initialize(HttpManager)

Initialize a new reuqest manager.

isConnected()

Is this cache connected to the net ?

isGarbageCollectionEnabled()

Are we allow to run garbage collections at all ?

isShared()

Is this cache shared among multiple users ?

loadResource(String)

Try to load from the cache the resource's whose URL is gievn.

markUsed(CachedResource)

markUsed(CachedResource, int)

markUsed(CachedResource, int, int)

Mark the given cached resource as having been used recently.

outgoingFilter(Request, Reply)

propertyChanged(String)

PropertyMonitoring implementation - Commit property changes.

pushDocument(Request, Reply)

Push a document in the cache.

removeResource(String)

Remove a resource from the cache.

setWarnings(Request, Reply)

Copy all warnings colllected into the given reply.

sync()

Save all cache related infos to stable storage.

trace(Request, String)

updateCacheSpaceCounter(int)

 protected static final int CACHEDIR_SPLITS

Number of sub-levels file system directories in the cache directory.

 public static final Integer HOW_HIT

STATE_HOW value - Indicates request fulfilled through a hot.

 public static final Integer HOW_MISS

STATE_HOW value - Indicates request fulfilled through a miss.

 public static final Integer HOW_REVALIDATION_SUCCESS

STATE_HOW value - indicates request fulfilled through sucessfull revalidation.

 public static final Integer HOW_REVALIDATION_FAILURE

STATE_HOW value - indicates request fulfilled through unsucessfull revalidation.

 public static final String STATE_HOW

Logging state - for some logger to keep track of what's happening.

 public static final String STATE_NOCACHE

The state used to disable that filter per request. Also set by the cache if the request cannot be fullfilled by caches, as detected by this filter.

 public static final String STATE_WARNINGS

Name of the request state used to collect warnings.

 public static final String STATE_ORIGREQ

Name of the request state used tokeep track of original request

 public static final String STATE_REVALIDATION

Name of the request state that marks a request as being a revalidation.

 public static final String STATE_CACHABLE

Name of the property that indicates that the cache cab be used.

 public static final String STATE_RESOURCE

 protected static HttpWarning WARN_DISCONNECTED

The HTTP warning used to notify of a disconnected cache.

 protected static HttpWarning WARN_STALE

The HTTP warning used to mark invalid entries

 protected static HttpWarning WARN_HEURISTIC

The HTTP warning used to indicate a heuristic expiration time.

 public static final String CACHE_SIZE_P

The name of the properties indicating the size of the cache (in bytes). This property will give the value of the disk-based cache size. This value only takes into account the size of the entities saved, not the size of the associated headers.

This property defaults to 5000000 bytes.

 public static final String DEBUG_P

Name of the property indicating if the cache is in debug mode.

This property defaults to false.

 public static final String SHARED_P

Name of the property indicating if this cache is shared.

This property defaults to true.

 public static final String CACHE_DIRECTORY_P

Name of the property giving the cache's directory. This property defaults to the current directory.

 public static final String CACHE_CONNECTED_P

Name of the property indicating wether the cache is connected or not. This property defaults to true.

 public static final String GARBAGE_COLLECTION_ENABLED_P

Name of the property enabling garbage collection of the cache. This property defaults to true.

 public static final String FILE_SIZE_RATIO_P

Name of the property indicating the max size for files to be cached. This property gives the ratio (relative to the cache size) of the number of bytes a single entry is able to occupy.

The ratio should be given as a floating point value between 0 and 1. If set to 0.1 and the cache size is 5000000, files larger then 500000 will not be cached (except if garbage collection is disbabled).

This property defaults to 0.1.

 protected ObservableProperties props

The properties we initialized ourself from.

 protected File directory

The directory where the cache is stored.

 protected int size

The current cache size.

 protected boolean debug

The debug flag.

 protected boolean shared

Is this cached shared ?

 protected boolean connected

Is this cache connected ?

 protected boolean garbageCollectionEnabled

Should we enable garbage collection of the cache ?

 protected double fileSizeRatio

The file size quota.

Indicates the percentage of cache size allowed to be occupied by a single file. This is not taken into account when garbage collection is disabled.

 protected long expires_drift

The expires drift.

Control if we will cache already expires documents, in the hope that revalidation will be enough to refresh them, or also because the cache will be used in disconnected mode.

 protected cacheStatistics stats

Our real time statistics.

 public CacheFilter()

 protected void addWarning(Request request,
                           HttpWarning warning)

Add a warning, to be emitted at reply time. The cache filter keeps track, through a specific piece of request state of the warnings to be emitted at reply time (if any).

During request processing, cached resources can add any kind of warnings, which will be collected and forwarded back to the reply.

Parameters:

request - The request being process, and whose reply requires some warnings.

warning - The warning to be emitted if ever we use the cache filter to answer the above request.

 protected final void setWarnings(Request request,
                                  Reply reply)

Copy all warnings colllected into the given reply. This method collects all HTTP warnings saved during request processing and create (if needed) the approporiate warning header in the given reply.

Parameters:

request - The request that has been processed by the cache filter.

reply - The reply that has been constructed from the cache.

See Also:

addWarning

 protected final void trace(Request request,
                            String msg)

 protected final void updateCacheSpaceCounter(int delta)

 public static String getHow(Request request)

Returns a String indicating what the cache did with that request.

Parameters:

request - A request that may have been processed through the cache filter

 public final boolean isShared()

Is this cache shared among multiple users ?

Returns:

A boolean true if shared, false otherwise.

 public final boolean isConnected()

Is this cache connected to the net ?

Returns:

A boolean, true if the cache is connected, false otherwise.

 public final boolean isGarbageCollectionEnabled()

Are we allow to run garbage collections at all ?

Returns:

A boolean true if garbage collection is allowed , false otherwise.

 protected File getFile(URL url)

Get a file to save that URL in.

Parameters:

url - The URL to be dumped.

Returns:

A File instance.

 protected void markUsed(CachedResource resource,
                         int osize,
                         int nsize)

Mark the given cached resource as having been used recently.

Parameters:

resource - The CachedResource instance that has been used.

 protected void markUsed(CachedResource resource,
                         int nsize)

 protected void markUsed(CachedResource resource)

 protected boolean checkCacheDirectory(File dir)

 protected File getSubdirectory(int i)

 public boolean propertyChanged(String name)

PropertyMonitoring implementation - Commit property changes.

Parameters:

name - The name of the property that has changed.

Returns:

A boolean true if change was commited, false otherwise.

 public final int getCacheSize()

Get the total size allocated to the cache.

Returns:

The cache size as an integer.

 public void initialize(HttpManager manager) throws PropRequestFilterException

Initialize a new reuqest manager. At this time, only one manager is allowed per application. This restriction will be removed either by using several managers, or by providing manager contexts.

Parameters:

manager - The manager to initialize.

Throws: FilterInitException

If the cache directory couldn't be created.

 public cacheStatistics getStatistics()

Get the statistics repository associated with that filter.

Returns:

An instance of cacheStatistics.

 public CachedResource loadResource(String url) throws InvalidResourceException

Try to load from the cache the resource's whose URL is gievn.

Parameters:

url - The String version of the url of the resource to load.

Returns:

An instance of CachedResource (or one of its subclasses), or null if not found.

 public boolean hasResource(String url)

Does the cache knows about this resource ?

Returns:

A boolean true if this resource is known, false otherwise.

 public void removeResource(String urlloc)

Remove a resource from the cache.

Parameters:

urlloc - The URL of the resource to remove, encoded as a String.

 public boolean canUseCache(Request request)

Can the given request be fullfilled by the cache filter ? This method distinguishes two situations. It first check if anything in the request makes it uncachable, if this is the case, processing continues normally. If the request can be answered by the cache, we mark it as such by setting the w3c.www.protocol.http.cache state of the request to Boolean.TRUE, ans we return true.

Returns:

A boolean, true if the request can be fullfilled by the cache, false otherwise.

 public boolean canCache(Request request,
                         Reply reply)

Can the given reply to the given request be added to the cache. This method performs all checks to detect wether the given request, reply can be cached.

We don't check for expires or maxage here, since we expect some sites to use negative expires, or zero max age, just for the sake of revalidation (that's fine).

Returns:

A boolean true if we can cache, false otherwise.

 public boolean exceptionFilter(Request request,
                                HttpException ex)

This filter doesn't handle exceptions.

Parameters:

request - The request that triggered the exception.

ex - The triggered exception.

Returns:

Always false.

 public Reply ingoingFilter(Request request) throws HttpException

 public Reply outgoingFilter(Request request,
                             Reply reply) throws HttpException

 public void pushDocument(Request request,
                          Reply reply)

Push a document in the cache. The caller has to forge a a request and a reply before being able to make something enter the cache. The request should provide at least:

URL

The URL (key for cache lookups)

Method

The method that was "applied" to URL to get forged reply.

It is recommended that the reply provides at least the following informations:

Status Code

A valid HTTP/1.1 status code (probably 200)

InputStream

Containing the entity to be cached,

EntityTag

A valid entity tag for the document,

CacheControl

Appropriate HTTP/1.1 cache controls for that document,

Mime headers

At least a valid content type, and probably a content length (to check consistency with the reply body).

sync

 public void sync()

Save all cache related infos to stable storage.

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