SLING-4609 add some more JSR 305 annotations

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1672913 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/src/main/java/org/apache/sling/validation/api/Validator.java b/src/main/java/org/apache/sling/validation/api/Validator.java
index 1d60ad6..b1c50ba 100644
--- a/src/main/java/org/apache/sling/validation/api/Validator.java
+++ b/src/main/java/org/apache/sling/validation/api/Validator.java
@@ -18,6 +18,9 @@
  */
 package org.apache.sling.validation.api;
 
+import javax.annotation.CheckForNull;
+import javax.annotation.Nonnull;
+
 import org.apache.sling.api.resource.ValueMap;
 import org.apache.sling.validation.api.exceptions.SlingValidationException;
 
@@ -69,5 +72,5 @@
      * @return validation error message if validation was not successful, {@code null} otherwise. In case an empty string is returned a generic validation error message is used.
      * @throws org.apache.sling.validation.api.exceptions.SlingValidationException if some expected arguments are missing from the arguments map
      */
-    String validate(T data, ValueMap valueMap, ValueMap arguments) throws SlingValidationException;
+    @CheckForNull String validate(@Nonnull T data, @Nonnull ValueMap valueMap, @Nonnull ValueMap arguments) throws SlingValidationException;
 }