// Copyright 2006, 2007, 2008 The Apache Software Foundation

 //

 // 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 org.apache.tapestry5.validator;

 import org.apache.tapestry5.Field;

 import org.apache.tapestry5.MarkupWriter;

 import org.apache.tapestry5.ValidationException;

 import org.apache.tapestry5.ioc.MessageFormatter;

 import org.apache.tapestry5.ioc.internal.util.InternalUtils;

 import org.apache.tapestry5.services.FormSupport;

 /**

  * A validator that enforces that the value is not null and not the empty string. This validator is not configurable.

  */

 public final class Required extends AbstractValidator<Void, Object>

 {

     public Required()

     {

         super(null, Object.class, "required");

     }

     public void validate(Field field, Void constraintValue, MessageFormatter formatter, Object value)

             throws ValidationException

     {

         if (value == null || InternalUtils.isBlank(value.toString()))

             throw new ValidationException(buildMessage(formatter, field));

     }

     private String buildMessage(MessageFormatter formatter, Field field)

     {

         return formatter.format(field.getLabel());

     }

     /**

      * The exception to the rule.

      */

     public boolean isRequired()

     {

         return true;

     }

     public void render(Field field, Void constraintValue, MessageFormatter formatter, MarkupWriter writer,

                        FormSupport formSupport)

     {

         formSupport.addValidation(field, "required", buildMessage(formatter, field), null);

     }

 }