org.apache.avalon.excalibur.source
Interface ModifiableSource

All Superinterfaces:

Source

All Known Implementing Classes:

URLSource

public interface ModifiableSource

extends Source

Describes a Source object whose data content can change. The overall handling of this object is very similar to the handling of the source object: using the getInputStream() method you get always the upto-date content. When you're done with using the source object, you have to release it. If you want to track changes of the source object, this interface offers you some support for it by providing a SourceValidity object. How does the caching work? The first time you get a ModifiableSource object, you simply ask it for it's content via getInputStream() and then get the validity object by invoking getValidity. (Further calls to getValidity always return the same object! This is not updated!) The caching algorithm can now store this validity object together with the system identifier of the source. The next time, the caching algorithm wants to check if the cached content is still valid. It has a validity object already to check against. If it is still the same ModifiableSource than the first time, you have to call discardValidity() in order to discard the stored validity in the ModifiableSource object. If it is a new ModifiableSource object, calling discardValidity() should do no harm. After that an upto-date validity object can retrieved by calling getValidity(). This can be used to test if the content is still valid as discribed in the source validity documentation. If the content is still valid, the cache knows what to do, if not, the new content can be get using getInputStream(). So either after a call to getValidity() or the getInputStream the validity object must be the same until discardValidity is called!

Author:

Ovidiu Predescu, Carsten Ziegeler

Method Summary

void	discardValidity() Refresh the content of this object after the underlying data content has changed.
SourceValidity	getValidity() Get the Validity object.

Methods inherited from interface org.apache.avalon.excalibur.source.Source

getInputStream, getSystemId

Method Detail

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.

discardValidity

public void discardValidity()

Refresh the content of this object after the underlying data content has changed.