[SHIBUI-580]

Added a simple POJO for transmitting errors from custom exception handlers.
Added a custom exception handler for when bad things happen when parsing JSON Resolvers.
Fixed a couple typos.

backend/src/main/java/edu/internet2/tier/shibboleth/admin/ui/controller/ErrorResponse.java

@@ -0,0 +1,18 @@
+package edu.internet2.tier.shibboleth.admin.ui.controller;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.Setter;
+import lombok.ToString;
+
+/**
+ * @author Bill Smith (wsmith@unicon.net)
+ */
+@AllArgsConstructor
+@Getter
+@Setter
+@ToString
+public class ErrorResponse {
+    private String errorCode;
+    private String errorMessage;
+}

backend/src/main/java/edu/internet2/tier/shibboleth/admin/ui/controller/MetadataResolversController.java

@@ -1,15 +1,16 @@
 package edu.internet2.tier.shibboleth.admin.ui.controller;
 
+import com.fasterxml.jackson.databind.exc.InvalidTypeIdException;
 import edu.internet2.tier.shibboleth.admin.ui.domain.resolvers.MetadataResolver;
 import edu.internet2.tier.shibboleth.admin.ui.domain.resolvers.MetadataResolverValidationService;
-import edu.internet2.tier.shibboleth.admin.ui.domain.resolvers.MetadataResolverValidator;
 import edu.internet2.tier.shibboleth.admin.ui.repository.MetadataResolverRepository;
-
 import lombok.extern.slf4j.Slf4j;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
+import org.springframework.http.converter.HttpMessageNotReadableException;
 import org.springframework.transaction.annotation.Transactional;
+import org.springframework.web.bind.annotation.ExceptionHandler;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.PostMapping;
@@ -19,6 +20,7 @@
 import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.servlet.support.ServletUriComponentsBuilder;
 
+import java.io.IOException;
 import java.net.URI;
 
 import static edu.internet2.tier.shibboleth.admin.ui.domain.resolvers.MetadataResolverValidator.ValidationResult;
@@ -34,6 +36,11 @@ public class MetadataResolversController {
     @Autowired
     MetadataResolverValidationService metadataResolverValidationService;
 
+    @ExceptionHandler({InvalidTypeIdException.class, IOException.class, HttpMessageNotReadableException.class})
+    public ResponseEntity<?> unableToParseJson(Exception ex) {
+        return ResponseEntity.badRequest().body(new ErrorResponse(HttpStatus.BAD_REQUEST.toString(), ex.getMessage()));
+    }
+
     @GetMapping("/MetadataResolvers")
     @Transactional(readOnly = true)
     public ResponseEntity<?> getAll() {

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

@@ -8,7 +8,7 @@
 
 /**
  * A facade that aggregates {@link MetadataResolverValidator}s available to call just one of them supporting the type of a given resolver.
- * If no {@link MetadataResolverValidator}s are configured, conciders provided MetadataResolver as valid.
+ * If no {@link MetadataResolverValidator}s are configured, considers provided MetadataResolver as valid.
  * <p>
  * Uses chain-of-responsibility design pattern
  *
@@ -22,7 +22,7 @@ public MetadataResolverValidationService(List<MetadataResolverValidator<T>> vali
         this.validators = validators != null ? validators : new ArrayList<>();
     }
 
-    @SuppressWarnings("Uncheked")
+    @SuppressWarnings("Unchecked")
     public ValidationResult validateIfNecessary(T metadataResolver) {
         Optional<MetadataResolverValidator<T>> validator =
                 this.validators