fix(notifications): more descriptive error responses for UI notificat…

…ions (#260)

src/main/java/io/cryostat/ExceptionMappers.java

@@ -18,6 +18,7 @@
 import org.openjdk.jmc.rjmx.ConnectionException;
 
 import io.cryostat.targets.TargetConnectionManager;
+import io.cryostat.util.EntityExistsException;
 
 import io.netty.handler.codec.http.HttpResponseStatus;
 import io.smallrye.mutiny.TimeoutException;
@@ -26,6 +27,7 @@
 import org.hibernate.exception.ConstraintViolationException;
 import org.jboss.logging.Logger;
 import org.jboss.resteasy.reactive.RestResponse;
+import org.jboss.resteasy.reactive.RestResponse.ResponseBuilder;
 import org.jboss.resteasy.reactive.server.ServerExceptionMapper;
 import org.projectnessie.cel.tools.ScriptException;
 import software.amazon.awssdk.services.s3.model.NoSuchKeyException;
@@ -90,4 +92,12 @@ public RestResponse<Void> mapMutinyTimeoutException(TimeoutException ex) {
         logger.warn(ex);
         return RestResponse.status(HttpResponseStatus.GATEWAY_TIMEOUT.code());
     }
+
+    @ServerExceptionMapper
+    public RestResponse<Object> mapEntityExistsException(EntityExistsException ex) {
+        logger.warn(ex);
+        return ResponseBuilder.create(HttpResponseStatus.CONFLICT.code())
+                .entity(ex.getMessage())
+                .build();
+    }
 }

src/main/java/io/cryostat/recordings/RecordingHelper.java

@@ -59,6 +59,7 @@
 import io.cryostat.recordings.Recordings.Metadata;
 import io.cryostat.targets.Target;
 import io.cryostat.targets.TargetConnectionManager;
+import io.cryostat.util.EntityExistsException;
 import io.cryostat.util.HttpMimeType;
 import io.cryostat.ws.MessagingServer;
 import io.cryostat.ws.Notification;
@@ -154,10 +155,7 @@ public ActiveRecording startRecording(
                             boolean restart =
                                     shouldRestartRecording(replace, previousState, recordingName);
                             if (!restart) {
-                                throw new BadRequestException(
-                                        String.format(
-                                                "Recording with name \"%s\" already exists",
-                                                recordingName));
+                                throw new EntityExistsException("Recording", recordingName);
                             }
                             if (!ActiveRecording.deleteFromTarget(target, recordingName)) {
                                 logger.warnf(

src/main/java/io/cryostat/rules/Rules.java

@@ -17,14 +17,14 @@
 
 import io.cryostat.V2Response;
 import io.cryostat.expressions.MatchExpression;
+import io.cryostat.util.EntityExistsException;
 
 import io.vertx.core.json.JsonObject;
 import io.vertx.mutiny.core.eventbus.EventBus;
 import jakarta.annotation.security.RolesAllowed;
 import jakarta.inject.Inject;
 import jakarta.transaction.Transactional;
 import jakarta.ws.rs.BadRequestException;
-import jakarta.ws.rs.ClientErrorException;
 import jakarta.ws.rs.Consumes;
 import jakarta.ws.rs.DELETE;
 import jakarta.ws.rs.GET;
@@ -69,7 +69,7 @@ public RestResponse<V2Response> create(Rule rule) {
         }
         boolean ruleExists = Rule.getByName(rule.name) != null;
         if (ruleExists) {
-            throw new RuleExistsException(rule.name);
+            throw new EntityExistsException("Rule", rule.name);
         }
         if (rule.description == null) {
             rule.description = "";
@@ -146,10 +146,4 @@ public RestResponse<V2Response> delete(@RestPath String name, @RestQuery boolean
         rule.delete();
         return RestResponse.ok(V2Response.json(Response.Status.OK, null));
     }
-
-    static class RuleExistsException extends ClientErrorException {
-        RuleExistsException(String ruleName) {
-            super("Rule with name " + ruleName + " already exists", Response.Status.CONFLICT);
-        }
-    }
 }

src/main/java/io/cryostat/util/EntityExistsException.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright The Cryostat Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.cryostat.util;
+
+import jakarta.ws.rs.ClientErrorException;
+import jakarta.ws.rs.core.Response;
+
+public class EntityExistsException extends ClientErrorException {
+    public EntityExistsException(String type, String name) {
+        super(
+                String.format(
+                        "%s with name %s already exists. Try again with a different name",
+                        type, name),
+                Response.Status.CONFLICT);
+    }
+}