# PetValidator.java

    /*
     * Copyright 2012-2019 the original author or 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
     *
     *      https://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.springframework.samples.petclinic.owner;

    import org.springframework.util.StringUtils;
    import org.springframework.validation.Errors;
    import org.springframework.validation.Validator;

    /**
     * <code>Validator</code> for <code>Pet</code> forms.
     * <p>
     * We're not using Bean Validation annotations here because it is easier to define such validation rule in Java.
     * </p>
     *
     * @author Ken Krebs
     * @author Juergen Hoeller
     */
    public class PetValidator implements Validator {

        private static final String REQUIRED = "required";

        @Override
        public void validate(Object obj, Errors errors) {
            Pet pet = (Pet) obj;
            String name = pet.getName();
            // name validation
            if (!StringUtils.hasLength(name)) {
                errors.rejectValue("name", REQUIRED, REQUIRED);
            }

            // type validation
            if (pet.isNew() && pet.getType() == null) {
                errors.rejectValue("type", REQUIRED, REQUIRED);
            }

            // birth date validation
            if (pet.getBirthDate() == null) {
                errors.rejectValue("birthDate", REQUIRED, REQUIRED);
            }
        }

        /**
         * This Validator validates *just* Pet instances
         */
        @Override
        public boolean supports(Class<?> clazz) {
            return Pet.class.isAssignableFrom(clazz);
        }

    }