Since version 2.0, Spring has featured a mechanism for schema-based extensions to the basic Spring XML format for defining and configuring beans. This section is devoted to detailing how you would go about writing your own custom XML bean definition parsers and integrating such parsers into the Spring IoC container.
To facilitate the authoring of configuration files using a schema-aware XML editor, Spring's extensible XML configuration mechanism is based on XML Schema. If you are not familiar with Spring's current XML configuration extensions that come with the standard Spring distribution, please first read the appendix entitled Appendix C, XML Schema-based configuration.
Creating new XML configuration extensions can be done by following these (relatively) simple steps:
Authoring an XML schema to describe your custom element(s).
Coding a custom NamespaceHandler
implementation (this is an easy step, don't worry).
Coding one or more BeanDefinitionParser
implementations (this is where the real work is done).
Registering the above artifacts with Spring (this too is an easy step).
What follows is a description of each of these steps. For the example, we will create
an XML extension (a custom XML element) that allows us to configure objects of the type
SimpleDateFormat (from the java.text package)
in an easy manner. When we are done, we will be able to define bean definitions of type
SimpleDateFormat like this:
<myns:dateformat id="dateFormat" pattern="yyyy-MM-dd HH:mm" lenient="true"/>
(Don't worry about the fact that this example is very simple; much more detailed examples follow afterwards. The intent in this first simple example is to walk you through the basic steps involved.)