    001    // Copyright 2006, 2007, 2008 The Apache Software Foundation
    002    //
    003    // Licensed under the Apache License, Version 2.0 (the "License");
    004    // you may not use this file except in compliance with the License.
    005    // You may obtain a copy of the License at
    006    //
    007    //     http://www.apache.org/licenses/LICENSE-2.0
    008    //
    009    // Unless required by applicable law or agreed to in writing, software
    010    // distributed under the License is distributed on an "AS IS" BASIS,
    011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    012    // See the License for the specific language governing permissions and
    013    // limitations under the License.
    014
    015    package org.apache.tapestry5.validator;
    016
    017    import org.apache.tapestry5.Field;
    018    import org.apache.tapestry5.MarkupWriter;
    019    import org.apache.tapestry5.ValidationException;
    020    import org.apache.tapestry5.ioc.MessageFormatter;
    021    import org.apache.tapestry5.ioc.internal.util.InternalUtils;
    022    import org.apache.tapestry5.services.FormSupport;
    023
    024    /**
    025     * A validator that enforces that the value is not null and not the empty string. This validator is not configurable.
    026     */
    027    public final class Required extends AbstractValidator<Void, Object>
    028    {
    029        public Required()
    030        {
    031            super(null, Object.class, "required");
    032        }
    033
    034        public void validate(Field field, Void constraintValue, MessageFormatter formatter, Object value)
    035                throws ValidationException
    036        {
    037            if (value == null || InternalUtils.isEmptyCollection(value) || InternalUtils.isBlank(value.toString()))
    038                throw new ValidationException(buildMessage(formatter, field));
    039        }
    040
    041        private String buildMessage(MessageFormatter formatter, Field field)
    042        {
    043            return formatter.format(field.getLabel());
    044        }
    045
    046        /**
    047         * The exception to the rule.
    048         */
    049        public boolean isRequired()
    050        {
    051            return true;
    052        }
    053
    054        public void render(Field field, Void constraintValue, MessageFormatter formatter, MarkupWriter writer,
    055                           FormSupport formSupport)
    056        {
    057            formSupport.addValidation(field, "required", buildMessage(formatter, field), null);
    058        }
    059    }