[#12]

rework validation
fix constructor to not add a message if null
use empty constructor if all is well

backend/src/main/java/edu/internet2/tier/shibboleth/admin/ui/domain/resolvers/MetadataResolverValidationService.java

@@ -28,9 +28,7 @@ public ValidationResult validateIfNecessary(T metadataResolver) {
         this.validators
                 .stream()
                 .filter(v -> v.supports(metadataResolver))
-                .forEach(v -> {
-                    validationResult.getErrorMessages().addAll(v.validate(metadataResolver).getErrorMessages());
-                });
+                .forEach(v -> v.validate(metadataResolver).getErrorMessages().stream().filter(m -> m != null).forEach(r -> validationResult.getErrorMessages().add(r)));
         return validationResult;
     }
 

backend/src/main/java/edu/internet2/tier/shibboleth/admin/ui/domain/resolvers/MetadataResolverValidator.java

@@ -23,7 +23,9 @@ class ValidationResult {
         public ValidationResult() {}
 
         public ValidationResult(String errorMessage) {
-            this.errorMessages.add(errorMessage);
+            if (errorMessage != null) {
+                this.errorMessages.add(errorMessage);
+            }
         }
 
         private List<String> errorMessages = new ArrayList<>();

backend/src/main/java/edu/internet2/tier/shibboleth/admin/ui/domain/resolvers/ResourceBackedMetadataResolverValidator.java

@@ -15,6 +15,6 @@ public ValidationResult validate(ResourceBackedMetadataResolver resolver) {
         catch (ResourceBackedMetadataResolver.InvalidResourceTypeException e) {
             return new ValidationResult(e.getMessage());
         }
-        return new ValidationResult(null);
+        return new ValidationResult();
     }
 }