Allow APIResponse on ExceptionMapper class

Allow the APIResponse annotation to be used on an exception mapper class
as well as the toResponse method.

api/src/main/java/org/eclipse/microprofile/openapi/annotations/responses/APIResponse.java

@@ -51,9 +51,9 @@
  * specified responseCode the response is not added to that operation.
  * 
  * <p>
- * When this annotation is applied to an <code>ExceptionMapper</code>, it allows developers to describe the API response
- * that will be added to a generated OpenAPI operation based on a JAX-RS method that declares an <code>Exception</code>
- * of the type handled by the <code>ExceptionMapper</code>.
+ * When this annotation is applied to an <code>ExceptionMapper</code> class or <code>toResponse</code> method, it allows
+ * developers to describe the API response that will be added to a generated OpenAPI operation based on a JAX-RS method
+ * that declares an <code>Exception</code> of the type handled by the <code>ExceptionMapper</code>.
  * 
  * <pre>
  * &#64;Provider

tck/src/main/java/org/eclipse/microprofile/openapi/apps/airlines/exception/ReviewRejectedException.java

@@ -0,0 +1,26 @@
+/**
+ * Copyright (c) 2022 Contributors to the Eclipse Foundation
+ * <p>
+ * 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
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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 org.eclipse.microprofile.openapi.apps.airlines.exception;
+
+@SuppressWarnings("serial")
+public class ReviewRejectedException extends Exception {
+
+    public ReviewRejectedException(String rejectionReason, Throwable cause) {
+        super(rejectionReason, cause);
+    }
+
+    public ReviewRejectedException(String rejectionReason) {
+        super(rejectionReason);
+    }
+
+}

tck/src/main/java/org/eclipse/microprofile/openapi/apps/airlines/exception/ReviewRejectedExceptionMapper.java

@@ -0,0 +1,48 @@
+/**
+ * Copyright (c) 2022 Contributors to the Eclipse Foundation
+ * <p>
+ * 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
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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 org.eclipse.microprofile.openapi.apps.airlines.exception;
+
+import org.eclipse.microprofile.openapi.annotations.media.Content;
+import org.eclipse.microprofile.openapi.annotations.media.Schema;
+import org.eclipse.microprofile.openapi.annotations.responses.APIResponse;
+import org.eclipse.microprofile.openapi.apps.airlines.exception.ReviewRejectedExceptionMapper.RejectionResponse;
+
+import jakarta.ws.rs.core.MediaType;
+import jakarta.ws.rs.core.Response;
+import jakarta.ws.rs.core.Response.Status;
+import jakarta.ws.rs.ext.ExceptionMapper;
+
+@APIResponse(responseCode = "400", description = "The review was rejected", content = @Content(mediaType = MediaType.APPLICATION_JSON, schema = @Schema(implementation = RejectionResponse.class)))
+public class ReviewRejectedExceptionMapper implements ExceptionMapper<ReviewRejectedException> {
+
+    @Override
+    public Response toResponse(ReviewRejectedException exception) {
+        RejectionResponse response = new RejectionResponse();
+        response.setReason(exception.getMessage());
+        return Response.status(Status.BAD_REQUEST).entity(response).build();
+    }
+
+    public static class RejectionResponse {
+        @Schema(description = "The reason the review was rejected")
+        private String reason;
+
+        public String getReason() {
+            return reason;
+        }
+
+        public void setReason(String reason) {
+            this.reason = reason;
+        }
+    }
+
+}

tck/src/main/java/org/eclipse/microprofile/openapi/tck/AirlinesAppTest.java

@@ -1029,6 +1029,14 @@ public void testExceptionMappers(String type) {
         vr.body("paths.'/user/{username}'.get.responses.'404'.description", equalTo("Not Found"));
 
         vr.body("paths.'/user/{id}'.get.responses.'404'.content.'application/json'.schema", notNullValue());
+
+        vr.body("paths.'/reviews'.post.responses.'400'.description'.schema", equalTo("The review was rejected"));
+        vr.body("paths.'/reviews'.post.responses.'400'.content.'application/json'.schema", notNullValue());
+
+        String rejectedReviewSchema =
+                dereference(vr, "paths.'/reviews'.post.responses.'400'.content.'application/json'.schema");
+        vr.body(rejectedReviewSchema + ".type", equalTo("object"));
+        vr.body(rejectedReviewSchema + ".properties", contains("reason"));
     }
 
 }