What is a WebLogic XML Registry and why does Sterling MCF ask me to configure one?

Answer

The WebLogic XML Registry is a facility for configuring and administering the XML resources of an instance of WebLogic Server. XML resources in WebLogic Server include the parser used by an application to parse XML data, the transformer used by an application to transform XML data, external entity resolution, and caching of external entities.

Primarily, the reason customers who use WebLogic are asked to create an XML Registry and "Change the Document Builder Factory, SAX Parser Factory, and Transformer Factory to start with "org" instead of "weblogic"" (as documented in the MCF 7x Installation Guide; MCF 8x has slightly modified steps) is to ensure that when WebLogic needs to build, parse, or transform XML data, it uses the Apache open-source applications instead of those shipped with WebLogic, e.g. org.apache.xerces.jaxp.SAXParserFactoryImpl instead of weblogic.apache.xerces.jaxp.SAXParserFactoryImpl.

Sterling tests its product to work with Apache XML-based applications and thus, documents the requirement to configure WebLogic to effectively override the use of its own XML-based applications. It would be in the customer's best interest to use these same supported Apache applications; not doing so can produce undefined results.

Note: Also see Article PRI49768, which states that sometimes, the cause of errors like these in the WebLogic log,

log4j:WARN No appenders could be found for logger (org.apache.beehive.netui.util.config.parser.NetUIConfigParser).
log4j:WARN Please initialize the log4j system properly.

is because an XML Registry has not yet been configured.