Is it possible to override a Spring Namespace handler? - spring

Question

SpringMVC comes with a 'mvc' namespace handled by (unsurprisingly) 'MvcNamespaceHandler', defined like this :
public class MvcNamespaceHandler extends NamespaceHandlerSupport {
public void init() {
registerBeanDefinitionParser("annotation-driven", new AnnotationDrivenBeanDefinitionParser());
registerBeanDefinitionParser("default-servlet-handler", new DefaultServletHandlerBeanDefinitionParser());
registerBeanDefinitionParser("interceptors", new InterceptorsBeanDefinitionParser());
registerBeanDefinitionParser("resources", new ResourcesBeanDefinitionParser());
registerBeanDefinitionParser("view-controller", new ViewControllerBeanDefinitionParser());
}
}
I would like to modify the behavior of the namespace so that mvc:resources element are handled by a custom ResourcesBeanDefinitionParser (in my case, to replace a ResourcesHttpRequestHandler, create by the bean definition parser, with a custom implementation).
I would like to know if it is possible to do that whithout going through the hassle of creating a brand new namespace (as described here http://static.springsource.org/spring/docs/2.0.x/reference/extensible-xml.html).
Thanks !

Answer 1

You can create a custom namespace to register a different ResourceHttpRequestHandler, but like you have said, it is definitely a good amount of work.
A better approach may be to simply define the bean explicitly in configuration this way, the ResourcesBeanDefinition essentially does this:
<bean name="resourceHandler" class="org.springframework.web.servlet.resource.ResourceHttpRequestHandler">
<property name="locations">
<list>
<value>/resources/</value>
</property>
</bean>
<bean class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
<property name="urlMap">
<map>
<entry key="/resources/**" value-ref="resourceHandler"/>
</map>
</property>
</bean>
You can simply replace the resourceHandler with your implementation here.

Answer 2

I've had this very same issue today (but for the context namespaceHandler). I've done it on a hacky way.
create a file named spring.handlers in your META-INF folder and put a declaration overriding the default schema. In your case, something like this:
http\://www.springframework.org/schema/mvc=org.springframework.web.servlet.config.MvcNamespaceHandler
for
http\://www.springframework.org/schema/mvc=YOURBEANPATH.
Perhaps you will need to declare the spring.handlers file inside a jar with a name that starts with a letter greater than 's' (in my case it was 't'), as spring will merge the spring.handlers definitions by the order they are found.
For debugging information, take a look at DefaultNamespaceHandlerResolver#getHandlerMappings.