Handle "If-Modified-Since" request headers in WSDL and XSD handlers

[snicoll]

HandlerAdapter#getLastModified is deprecated so we need to adapt the following:

spring-ws/spring-ws-core/src/main/java/org/springframework/ws/transport/http/MessageDispatcherServlet.java

Lines 326 to 336 in fb4ab82

	protected long getLastModified(HttpServletRequest httpServletRequest) {
	WsdlDefinition definition = getWsdlDefinition(httpServletRequest);
	if (definition != null) {
	return wsdlDefinitionHandlerAdapter.getLastModified(httpServletRequest, definition);
	}
	XsdSchema schema = getXsdSchema(httpServletRequest);
	if (schema != null) {
	return xsdSchemaHandlerAdapter.getLastModified(httpServletRequest, schema);
	}
	return messageReceiverHandlerAdapter.getLastModified(httpServletRequest, messageReceiver);
	}

[rstoyanchev]

The call to xsdSchemaHandlerAdapter could probably get inlined:

XsdSchema schema = getXsdSchema(httpServletRequest);
if (schema != null) {
    return LastModifiedHelper.getLastModified(schema.getSource())
}

The call to messageReceiverHandlerAdapter returns -1, so it seems to mainly about subclasses overriding it potentially, but given the deprecation, unless there are specific objections, it could probably be just dropped.

[snicoll]

Removing the deprecation turned out to improve our current support. Rather than having the servlet implement getLastModified we rely on Spring to compute if the request should be handled via ServletWebRequest#checkNotModified. This has the impact "If-Modified-Since" request headers are now taken into account.