added warning about annotated controller interfaces (SPR-6655)

org.springframework.web/src/main/java/org/springframework/web/bind/annotation/RequestMapping.java

 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2010 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -168,6 +168,11 @@ import java.lang.annotation.Target;
  * and/or <code>AnnotationMethodHandlerAdapter</code> is defined as well
  * - provided that you intend to use <code>@RequestMapping</code>.
  *
+ * <p><b>NOTE:</b> When using controller interfaces (e.g. for AOP proxying),
+ * make sure to consistently put <i>all</i> your mapping annotations - such as
+ * <code>@RequestMapping</code> and <code>@SessionAttributes</code> - on
+ * the controller <i>interface</i> rather than on the implementation class.
+ *
  * @author Juergen Hoeller
  * @author Arjen Poutsma
  * @author Sam Brannen

org.springframework.web/src/main/java/org/springframework/web/bind/annotation/SessionAttributes.java

 /*
- * Copyright 2002-2008 the original author or authors.
+ * Copyright 2002-2010 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -43,6 +43,11 @@ import java.lang.annotation.Target;
  * Alternatively, consider using the attribute management capabilities of the
  * generic {@link org.springframework.web.context.request.WebRequest} interface.
  *
+ * <p><b>NOTE:</b> When using controller interfaces (e.g. for AOP proxying),
+ * make sure to consistently put <i>all</i> your mapping annotations - such as
+ * <code>@RequestMapping</code> and <code>@SessionAttributes</code> - on
+ * the controller <i>interface</i> rather than on the implementation class.
+ *
  * @author Juergen Hoeller
  * @since 2.5
  */

spring-framework-reference/src/mvc.xml

@@ -1390,6 +1390,15 @@ public class EditPetForm {
 public class EditPetForm {
     <lineannotation>// ...</lineannotation>
 }</programlisting>
+
+        <note>
+          <para>When using controller interfaces (e.g. for AOP proxying), make sure to
+          consistently put <emphasis>all</emphasis> your mapping annotations - such as
+          <interfacename>@RequestMapping</interfacename> and
+          <interfacename>@SessionAttributes</interfacename> - on the controller
+          <emphasis>interface</emphasis> rather than on the implementation class.
+          </para>
+        </note>
       </section>
 
       <section id="mvc-ann-cookievalue">