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
015package org.apache.tapestry5.validator;
016
017import org.apache.tapestry5.Field;
018import org.apache.tapestry5.MarkupWriter;
019import org.apache.tapestry5.ValidationException;
020import org.apache.tapestry5.ioc.MessageFormatter;
021import org.apache.tapestry5.ioc.internal.util.InternalUtils;
022import 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 */
027public 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}