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Creates and returns Objects based on a set of Apache Digester rules in a consistent manner, providing validation in
the process.
This XML object factory allows us to define a consistent/clean of configuring java objects from XML configuration
files (i.e. it uses the class name of the java object to find what rule file and what XSD file to use). It also
allows us to define a consistent way in which schema validation is performed.
It seperates each concern into one file, for example: to configure and perform validation on the MetafacadeMappings
class, we need 3 files 1.) the java object (MetafacadeMappings.java), 2.) the rules file which tells the apache
digester how to populate the java object from the XML configuration file (MetafacadeMappings-Rules.xml), and 3.) the
XSD schema validation file (MetafacadeMappings.xsd). Note that each file is based on the name of the java object:
'java object name'.xsd and 'java object name'-Rules.xml'. After you have these three files then you just need to call
the method #getInstance(java.net.URL objectClass) in this class from the java object you want to configure. This
keeps the dependency to digester (or whatever XML configuration tool we are using at the time) to this single file.
In order to add/modify an existing element/attribute in your configuration file, first make the modification in your
java object, then modify it's rules file to instruct the digester on how to configure your new attribute/method in
the java object, and then modify your XSD file to provide correct validation for this new method/attribute. Please
see the org.andromda.core.metafacade.MetafacadeMappings* files for an example on how to do this.
author:
Chad Brandon | 