relaxed warning about ambiguous setters to only be logged in case of actual write access (SPR-6399)

org.springframework.beans/src/main/java/org/springframework/beans/BeanWrapperImpl.java

@@ -1060,7 +1060,9 @@ public class BeanWrapperImpl extends AbstractPropertyAccessor implements BeanWra
 					}
 					pv.getOriginalPropertyValue().conversionNecessary = (valueToApply != originalValue);
 				}
-				final Method writeMethod = pd.getWriteMethod();
+				final Method writeMethod = (pd instanceof GenericTypeAwarePropertyDescriptor ?
+						((GenericTypeAwarePropertyDescriptor) pd).getWriteMethodForActualAccess() :
+						pd.getWriteMethod());
 				if (!Modifier.isPublic(writeMethod.getDeclaringClass().getModifiers()) && !writeMethod.isAccessible()) {
 					if (System.getSecurityManager()!= null) {
 						AccessController.doPrivileged(new PrivilegedAction<Object>() {

org.springframework.beans/src/main/java/org/springframework/beans/GenericTypeAwarePropertyDescriptor.java

@@ -100,6 +100,10 @@ class GenericTypeAwarePropertyDescriptor extends PropertyDescriptor {
 
 	@Override
 	public Method getWriteMethod() {
+		return this.writeMethod;
+	}
+
+	public Method getWriteMethodForActualAccess() {
 		Set<Method> ambiguousCandidates = this.ambiguousWriteMethods;
 		if (ambiguousCandidates != null) {
 			this.ambiguousWriteMethods = null;