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org.apache.cocoon.components.source.impl
Class CachingSource

java.lang.Object
  org.apache.avalon.framework.logger.AbstractLogEnabled
      org.apache.cocoon.components.source.impl.CachingSource

All Implemented Interfaces:

Initializable, LogEnabled, Serviceable, Source, XMLizable

Direct Known Subclasses:

TraversableCachingSource

public class CachingSource
extends AbstractLogEnabled
implements Serviceable, Initializable, XMLizable, Source

This class implements a proxy like source that uses another source to get the content. This implementation can cache the content for a given period of time.

Syntax for Protocol

   cached:http://www.apache.org/[?cocoon:cache-expires=60&cocoon:cache-name=main]
 

The above examples show how the real source http://www.apache.org is wrapped and the cached contents is used for 60 seconds. The second querystring parameter instructs that the cache key be extended with the string main. This allows the use of multiple cache entries for the same source.

The value of the expires parameter holds some additional semantics. Specifying -1 will yield the cached response to be considered valid always. Value 0 can be used to achieve the exact opposite. That is to say, the cached contents will be thrown out and updated immediately and unconditionally.

Version:

$Id: CachingSource.html 1304258 2012-03-23 10:09:27Z ilgrosso $

Nested Class Summary

protected static class

CachingSource.SourceMeta Data holder for caching Source meta info.

Field Summary

protected boolean	async asynchronic refresh strategy ?
protected Cache	cache The current cache
static String	CACHE_EXPIRES_PARAM
static String	CACHE_NAME_PARAM
protected IdentifierCacheKey	cacheKey The key used in the store
protected String	cacheName cache key extension
protected boolean	eventAware
protected int	expires number of seconds before cached object becomes invalid
protected ServiceManager	manager The ServiceManager
protected String	protocol The used protocol
protected Source	source The source object for the real content
protected String	sourceUri The full URI string of the underlying source
protected String	uri The full URI string

Constructor Summary

CachingSource(String protocol, String uri, String sourceUri, Source source, int expires, String cacheName, boolean async, boolean eventAware)
Construct a new object.

Method Summary

void	dispose() Cleanup.
boolean	exists()
protected byte[]	getBinaryResponse() Initialize the cached response with meta and binary contents.
protected String	getCacheKey() Return the used key.
protected SourceValidity[]	getCacheValidities()
long	getContentLength() Get the content length of the source or -1 if it is not possible to determine the length.
protected long	getExpiration() Expires (in milli-seconds)
InputStream	getInputStream() Return an InputStream object to read from the source.
long	getLastModified() Get the last modification date.
String	getMimeType() The mime-type of the content described by this object.
protected CachingSource.SourceMeta	getResponseMeta() Initialize the cached response with meta info.
String	getScheme() Return the protocol identifier.
protected String	getSourceURI() Return the uri of the cached source.
String	getURI() Return the unique identifer for this source
SourceValidity	getValidity() Get the Validity object.
protected byte[]	getXMLResponse() Initialize the cached response with meta, binary, and XML contents.
void	initialize() Initialize the Source.
protected byte[]	readBinaryResponse(Source source) Read binary content from source.
protected CachingSource.SourceMeta	readMeta(Source source) Read meta data from source.
protected byte[]	readXMLResponse(Source source, byte[] binary, ServiceManager manager) Read XML content from source.
void	refresh() Refresh this object and update the last modified date and content length.
void	service(ServiceManager manager) Set the ServiceManager.
void	toSAX(ContentHandler contentHandler) Generates SAX events representing the object's state.

Methods inherited from class org.apache.avalon.framework.logger.AbstractLogEnabled

enableLogging, getLogger, setupLogger, setupLogger, setupLogger

Methods inherited from class java.lang.Object

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

Field Detail

CACHE_EXPIRES_PARAM

public static final String CACHE_EXPIRES_PARAM

See Also:

Constant Field Values

CACHE_NAME_PARAM

public static final String CACHE_NAME_PARAM

See Also:

Constant Field Values

protocol

protected final String protocol

The used protocol

uri

protected final String uri

The full URI string

sourceUri

protected final String sourceUri

The full URI string of the underlying source

source

protected Source source

The source object for the real content

manager

protected ServiceManager manager

The ServiceManager

cache

protected Cache cache

The current cache

cacheKey

protected final IdentifierCacheKey cacheKey

The key used in the store

expires

protected final int expires

number of seconds before cached object becomes invalid

cacheName

protected final String cacheName

cache key extension

async

protected final boolean async

asynchronic refresh strategy ?

eventAware

protected final boolean eventAware

Constructor Detail

CachingSource

public CachingSource(String protocol,
                     String uri,
                     String sourceUri,
                     Source source,
                     int expires,
                     String cacheName,
                     boolean async,
                     boolean eventAware)

Construct a new object.

Method Detail

service

public void service(ServiceManager manager)
             throws ServiceException

Set the ServiceManager.

Specified by:

service in interface Serviceable

Throws:

ServiceException

initialize

public void initialize()
                throws Exception

Initialize the Source.

Specified by:

initialize in interface Initializable

Throws:

Exception

dispose

public void dispose()

Cleanup.

getResponseMeta

protected CachingSource.SourceMeta getResponseMeta()
                                            throws IOException

Initialize the cached response with meta info.

Throws:

IOException - if an the binary response could not be initialized

getBinaryResponse

protected byte[] getBinaryResponse()
                            throws IOException

Initialize the cached response with meta and binary contents.

Throws:

IOException - if an the binary response could not be initialized

getXMLResponse

protected byte[] getXMLResponse()
                         throws SAXException,
                                IOException,
                                CascadingIOException

Initialize the cached response with meta, binary, and XML contents.

Throws:

SAXException - if something happened during xml processing

IOException - if an IO level error occured

CascadingIOException - wraps all other exception types

getScheme

public String getScheme()

Return the protocol identifier.

Specified by:

getScheme in interface Source

getContentLength

public long getContentLength()

Get the content length of the source or -1 if it is not possible to determine the length.

Specified by:

getContentLength in interface Source

getLastModified

public long getLastModified()

Get the last modification date.

Specified by:

getLastModified in interface Source

Returns:

The last modification in milliseconds since January 1, 1970 GMT or 0 if it is unknown

getMimeType

public String getMimeType()

The mime-type of the content described by this object. If the source is not able to determine the mime-type by itself this can be null.

Specified by:

getMimeType in interface Source

getInputStream

public InputStream getInputStream()
                           throws IOException,
                                  SourceException

Return an InputStream object to read from the source.

Specified by:

getInputStream in interface Source

Throws:

IOException

SourceException

getURI

public String getURI()

Return the unique identifer for this source

Specified by:

getURI in interface Source

exists

public boolean exists()

Specified by:

exists in interface Source

See Also:

Source.exists()

getValidity

public SourceValidity getValidity()

Get the Validity object. This can either wrap the last modification date or the expires information or... If it is currently not possible to calculate such an information null is returned.

Specified by:

getValidity in interface Source

refresh

public void refresh()

Refresh this object and update the last modified date and content length. This method will try to refresh the cached meta data and content only if cached content is expired.

Specified by:

refresh in interface Source

toSAX

public void toSAX(ContentHandler contentHandler)
           throws SAXException

Generates SAX events representing the object's state.

Specified by:

toSAX in interface XMLizable

Throws:

SAXException

getSourceURI

protected String getSourceURI()

Return the uri of the cached source.

getCacheKey

protected String getCacheKey()

Return the used key.

getExpiration

protected long getExpiration()

Expires (in milli-seconds)

readXMLResponse

protected byte[] readXMLResponse(Source source,
                                 byte[] binary,
                                 ServiceManager manager)
                          throws SAXException,
                                 IOException,
                                 CascadingIOException

Read XML content from source.

Returns:

content from source

Throws:

SAXException

IOException

CascadingIOException

readBinaryResponse

protected byte[] readBinaryResponse(Source source)
                             throws IOException,
                                    SourceNotFoundException

Read binary content from source.

Returns:

content from source

Throws:

IOException

SourceNotFoundException

readMeta

protected CachingSource.SourceMeta readMeta(Source source)
                                     throws SourceException

Read meta data from source.

Throws:

SourceException

getCacheValidities

protected SourceValidity[] getCacheValidities()