Implement factory methods for ValidationException (#41993)

Implement factory methods for ValidationException to make the client code more concise (1 LOC vs 3 LOC for a single error scenario)

client/rest-high-level/src/main/java/org/elasticsearch/client/ValidationException.java

@@ -21,12 +21,36 @@
 import org.elasticsearch.common.Nullable;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 
 /**
  * Encapsulates an accumulation of validation errors
  */
 public class ValidationException extends IllegalArgumentException {
+
+    /**
+     * Creates {@link ValidationException} instance initialized with given error messages.
+     * @param error the errors to add
+     * @return {@link ValidationException} instance
+     */
+    public static ValidationException withError(String... error) {
+        return withErrors(Arrays.asList(error));
+    }
+
+    /**
+     * Creates {@link ValidationException} instance initialized with given error messages.
+     * @param errors the list of errors to add
+     * @return {@link ValidationException} instance
+     */
+    public static ValidationException withErrors(List<String> errors) {
+        ValidationException e = new ValidationException();
+        for (String error : errors) {
+            e.addValidationError(error);
+        }
+        return e;
+    }
+
     private final List<String> validationErrors = new ArrayList<>();
 
     /**

client/rest-high-level/src/test/java/org/elasticsearch/client/ValidationExceptionTests.java

@@ -0,0 +1,56 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you 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 org.elasticsearch.client;
+
+import org.elasticsearch.test.ESTestCase;
+
+import java.util.Arrays;
+
+import static org.hamcrest.Matchers.contains;
+import static org.hamcrest.Matchers.hasSize;
+
+public class ValidationExceptionTests extends ESTestCase {
+
+    private static final String ERROR = "some-error";
+    private static final String OTHER_ERROR = "some-other-error";
+
+    public void testWithError() {
+        ValidationException e = ValidationException.withError(ERROR, OTHER_ERROR);
+        assertThat(e.validationErrors(), hasSize(2));
+        assertThat(e.validationErrors(), contains(ERROR, OTHER_ERROR));
+    }
+
+    public void testWithErrors() {
+        ValidationException e = ValidationException.withErrors(Arrays.asList(ERROR, OTHER_ERROR));
+        assertThat(e.validationErrors(), hasSize(2));
+        assertThat(e.validationErrors(), contains(ERROR, OTHER_ERROR));
+    }
+
+    public void testAddValidationError() {
+        ValidationException e = new ValidationException();
+        assertThat(e.validationErrors(), hasSize(0));
+        e.addValidationError(ERROR);
+        assertThat(e.validationErrors(), hasSize(1));
+        assertThat(e.validationErrors(), contains(ERROR));
+        e.addValidationError(OTHER_ERROR);
+        assertThat(e.validationErrors(), hasSize(2));
+        assertThat(e.validationErrors(), contains(ERROR, OTHER_ERROR));
+    }
+}