Resource locations can be specified either in-line or in external catalog file(s), or both. In order to use an external catalog file, the xml-commons resolver library ("resolver.jar") must be in your classpath. External catalog files may be either plain text format or XML format. If the xml-commons resolver library is not found in the classpath, external catalog files, specified in <catalogpath> paths, will be ignored and a warning will be logged. In this case, however, processing of inline entries will proceed normally.
Currently, only <dtd> and <entity> elements may be specified inline; these correspond to OASIS catalog entry types PUBLIC and URI respectively.
The following is a usage example:
<xmlcatalog>
<dtd publicId="" location="/path/to/file.jar" />
<dtd publicId="" location="/path/to/file2.jar" />
<entity publicId="" location="/path/to/file3.jar" />
<entity publicId="" location="/path/to/file4.jar" />
<catalogpath>
<pathelement location="/etc/sgml/catalog"/>
</catalogpath>
<catalogfiles dir="/opt/catalogs/" includes="**\catalog.xml" />
</xmlcatalog>
Tasks wishing to use <xmlcatalog> must provide a method called createXMLCatalog which returns an instance of XMLCatalog. Nested DTD and entity definitions are handled by the XMLCatalog object and must be labeled dtd and entity respectively.
The following is a description of the resolution algorithm: entities/URIs/dtds are looked up in each of the following contexts, stopping when a valid and readable resource is found:
See {@link org.apache.tools.ant.taskdefs.optional.XMLValidateTask XMLValidateTask} for an example of a task that has integratedsupport for XMLCatalogs.
Possible future extension could provide for additional OASIS entry types to be specified inline.
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