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org.dspace.content.crosswalk
Class XHTMLHeadDisseminationCrosswalk

java.lang.Object
  extended by org.dspace.core.SelfNamedPlugin
      extended by org.dspace.content.crosswalk.XHTMLHeadDisseminationCrosswalk
All Implemented Interfaces:
DisseminationCrosswalk
public class XHTMLHeadDisseminationCrosswalk
extends SelfNamedPlugin
implements DisseminationCrosswalk

Crosswalk for creating appropriate <meta> elements to appear in the item display page for a particular item, for improving automated processing of the page (e.g. by search engines). The metadata included should be as rich yet standards-compliant as possible.

The configuration file ${dspace.dir}/config/xhtml-head-item.properties contains the relevant mappings. Note: where there is a custom qualifier for which no corresponding mapping exists, the crosswalk will remove the qualifier and try again with just the element.

e.g. if a field exists in the database "dc.contributor.editor", and there is no dc.contributor.editor property below, the mapping for "dc.contributor" will be used. If an element in the item metadata record does not appear in the configuration, it is simply ignored; the emphasis here is on exposing standards-compliant metadata.

TODO: This may usefully be extended later to work with communities and collections.

Version:
$Revision$
Author:
Robert Tansley

Field Summary
 
Fields inherited from interface org.dspace.content.crosswalk.DisseminationCrosswalk
XSI_NS
 
Constructor Summary
XHTMLHeadDisseminationCrosswalk()
           
 
Method Summary
 boolean canDisseminate(DSpaceObject dso)
          Predicate: Can this disseminator crosswalk the given object.
 org.jdom.Element disseminateElement(DSpaceObject dso)
          This generates a <head> element around the metadata; in general this will probably not be used
 List disseminateList(DSpaceObject dso)
          Return <meta> elements that can be put in the <head> element of an XHTML document.
 org.jdom.Namespace[] getNamespaces()
          Get XML namespaces of the elements this crosswalk may return.
static String[] getPluginNames()
           
 String getSchemaLocation()
          Get the XML Schema location(s) of the target metadata format.
 boolean preferList()
          Predicate: Does this disseminator prefer to return a list of Elements, rather than a single root Element?
 
Methods inherited from class org.dspace.core.SelfNamedPlugin
getPluginInstanceName, setPluginInstanceName
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

XHTMLHeadDisseminationCrosswalk

public XHTMLHeadDisseminationCrosswalk()
                                throws IOException
Throws:
IOException
Method Detail

canDisseminate

public boolean canDisseminate(DSpaceObject dso)
Description copied from interface: DisseminationCrosswalk
Predicate: Can this disseminator crosswalk the given object. Needed by OAI-PMH server implementation.

Specified by:
canDisseminate in interface DisseminationCrosswalk
Parameters:
dso - dspace object, e.g. an Item.
Returns:
true when disseminator is capable of producing metadata.

disseminateElement

public org.jdom.Element disseminateElement(DSpaceObject dso)
                                    throws CrosswalkException,
                                           IOException,
                                           SQLException,
                                           AuthorizeException
This generates a <head> element around the metadata; in general this will probably not be used

Specified by:
disseminateElement in interface DisseminationCrosswalk
Parameters:
dso - the DSpace Object whose metadata to export.
Returns:
root Element of the target metadata, never null
Throws:
CrosswalkInternalException - (CrosswalkException) failure of the crosswalk itself.
CrosswalkObjectNotSupported - (CrosswalkException) Cannot crosswalk this kind of DSpace object.
IOException - I/O failure in services this calls
SQLException - Database failure in services this calls
AuthorizeException - current user not authorized for this operation.
CrosswalkException

disseminateList

public List disseminateList(DSpaceObject dso)
                     throws CrosswalkException,
                            IOException,
                            SQLException,
                            AuthorizeException
Return <meta> elements that can be put in the <head> element of an XHTML document.

Specified by:
disseminateList in interface DisseminationCrosswalk
Parameters:
dso - the DSpace Object whose metadata to export.
Returns:
results of crosswalk as list of XML elements.
Throws:
CrosswalkInternalException - (CrosswalkException) failure of the crosswalk itself.
CrosswalkObjectNotSupported - (CrosswalkException) Cannot crosswalk this kind of DSpace object.
IOException - I/O failure in services this calls
SQLException - Database failure in services this calls
AuthorizeException - current user not authorized for this operation.
CrosswalkException

getNamespaces

public org.jdom.Namespace[] getNamespaces()
Description copied from interface: DisseminationCrosswalk
Get XML namespaces of the elements this crosswalk may return. Returns the XML namespaces (as JDOM objects) of the root element.

Specified by:
getNamespaces in interface DisseminationCrosswalk
Returns:
array of namespaces, which may be empty.

getSchemaLocation

public String getSchemaLocation()
Description copied from interface: DisseminationCrosswalk
Get the XML Schema location(s) of the target metadata format. Returns the string value of the xsi:schemaLocation attribute that should be applied to the generated XML.

It may return the empty string if no schema is known, but crosswalk authors are strongly encouraged to implement this call so their output XML can be validated correctly.

Specified by:
getSchemaLocation in interface DisseminationCrosswalk
Returns:
SchemaLocation string, including URI namespace, followed by whitespace and URI of XML schema document, or empty string if unknown.

preferList

public boolean preferList()
Description copied from interface: DisseminationCrosswalk
Predicate: Does this disseminator prefer to return a list of Elements, rather than a single root Element?

Some metadata formats have an XML schema without a root element, for example, the Dublin Core and Qualified Dublin Core formats. This would be true for a crosswalk into QDC, since it would "prefer" to return a list, since any root element it has to produce would have to be part of a nonstandard schema. In most cases your implementation will want to return false

Specified by:
preferList in interface DisseminationCrosswalk
Returns:
true when disseminator prefers you call disseminateList().

getPluginNames

public static String[] getPluginNames()
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