Use springFrameworkVersion property in docs links

Closes gh-9987

docs/manual/spring-security-docs-manual.gradle

@@ -21,10 +21,10 @@ asciidoctorj {
 	def ghSamplesUrl = "https://github.com/spring-projects/spring-security-samples/tree/$samplesBranch"
 	def securityDocsUrl = "https://docs.spring.io/spring-security/site/docs/$docsTag"
 	def oldSecurityApiUrl = "https://docs.spring.io/spring-security/site/docs/5.4.x/api/"
-	def springVersion = "5.3.x"
 	def securityApiUrl = "$securityDocsUrl/api/"
 	def securityReferenceUrl = "$securityDocsUrl/reference/html5/"
-	def springFrameworkApiUrl = "https://docs.spring.io/spring-framework/docs/$springVersion/javadoc-api/"
+	def springFrameworkApiUrl = "https://docs.spring.io/spring-framework/docs/$springFrameworkVersion/javadoc-api/"
+	def springFrameworkReferenceUrl = "https://docs.spring.io/spring-framework/docs/$springFrameworkVersion/reference/html/"
 	attributes 'spring-security-version' : project.version,
 		'spring-boot-version' : springBootVersion,
 		revnumber : project.version,
@@ -34,7 +34,8 @@ asciidoctorj {
 		'old-security-api-url': oldSecurityApiUrl,
 		'security-api-url': securityApiUrl,
 		'security-reference-url': securityReferenceUrl,
-		'spring-framework-api-url': springFrameworkApiUrl
+		'spring-framework-api-url': springFrameworkApiUrl,
+		'spring-framework-reference-url': springFrameworkReferenceUrl
 	attributeProvider resolvedVersions(project.configurations.testRuntimeClasspath)
 }
 

docs/manual/src/docs/asciidoc/_includes/servlet/architecture/filters.adoc

@@ -9,7 +9,7 @@ The picture below shows the typical layering of the handlers for a single HTTP r
 image::{figures}/filterchain.png[]
 
 The client sends a request to the application, and the container creates a `FilterChain` which contains the ``Filter``s and `Servlet` that should process the `HttpServletRequest` based on the path of the request URI.
-In a Spring MVC application the `Servlet` is an instance of https://docs.spring.io/spring/docs/current/spring-framework-reference/web.html#mvc-servlet[`DispatcherServlet`].
+In a Spring MVC application the `Servlet` is an instance of {spring-framework-reference-url}web.html#mvc-servlet[`DispatcherServlet`].
 At most one `Servlet` can handle a single `HttpServletRequest` and `HttpServletResponse`.
 However, more than one `Filter` can be used to: