SEC-1448: Fixed failure to resolve generic method argument names in MethodSecurityEvaluationContext.

Changed to use AopUtils.getMostSpecificMethod() when obtaining the method on which the parameter resolution should be performed. Also added better error handling and log warning when parameter names cannot be resolved. The exception will then be a SpEL one, rather than a NPE.

core/src/main/java/org/springframework/security/access/expression/method/MethodSecurityEvaluationContext.java

@@ -3,11 +3,13 @@ package org.springframework.security.access.expression.method;
 import java.lang.reflect.Method;
 
 import org.aopalliance.intercept.MethodInvocation;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.springframework.aop.support.AopUtils;
 import org.springframework.core.LocalVariableTableParameterNameDiscoverer;
 import org.springframework.core.ParameterNameDiscoverer;
 import org.springframework.expression.spel.support.StandardEvaluationContext;
 import org.springframework.security.core.Authentication;
-import org.springframework.util.ClassUtils;
 
 /**
  * Internal security-specific EvaluationContext implementation which lazily adds the
@@ -18,6 +20,8 @@ import org.springframework.util.ClassUtils;
  * @since 3.0
  */
 class MethodSecurityEvaluationContext extends StandardEvaluationContext {
+    private static Log logger = LogFactory.getLog(MethodSecurityEvaluationContext.class);
+
     private ParameterNameDiscoverer parameterNameDiscoverer;
     private boolean argumentsAdded;
     private MethodInvocation mi;
@@ -58,10 +62,21 @@ class MethodSecurityEvaluationContext extends StandardEvaluationContext {
 
     private void addArgumentsAsVariables() {
         Object[] args = mi.getArguments();
+
+        if (args.length == 0) {
+            return;
+        }
+
         Object targetObject = mi.getThis();
-        Method method = ClassUtils.getMostSpecificMethod(mi.getMethod(), targetObject.getClass());
+        Method method = AopUtils.getMostSpecificMethod(mi.getMethod(), targetObject.getClass());
         String[] paramNames = parameterNameDiscoverer.getParameterNames(method);
 
+        if (paramNames == null) {
+            logger.warn("Unable to resolve method parameter names for method: " + method
+                    + ". Debug symbol information is required if you are using parameter names in expressions.");
+            return;
+        }
+
         for(int i=0; i < args.length; i++) {
             super.setVariable(paramNames[i], args[i]);
         }