001    // Copyright 2005 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.tapestry.form;
016    
017    import org.apache.tapestry.IMarkupWriter;
018    import org.apache.tapestry.IRequestCycle;
019    import org.apache.tapestry.form.validator.Required;
020    import org.apache.tapestry.valid.ValidatorException;
021    
022    /**
023     * Implements the logic used by {@link Required}s for required field checking on rewind and
024     * generating client-side logic during render.
025     * 
026     * @author Paul Ferraro
027     * @since 4.0
028     */
029    public interface ValidatableFieldSupport
030    {
031        /**
032         * Called during render of the specified component. Renders any contributions from validators.
033         */
034        void renderContributions(ValidatableField field, IMarkupWriter writer,
035                IRequestCycle cycle);
036    
037        /**
038         * Called during rewind of the specified component. Specified value is validated using the 
039         * component's validators.
040         * 
041         * @throws ValidatorException if validation fails
042         */
043        void validate(ValidatableField component, IMarkupWriter writer, IRequestCycle cycle, Object value) throws ValidatorException;
044    
045        /**
046         * Returns true if this component is required. This usually entails a search of the component's
047         * validators.
048         */
049        boolean isRequired(ValidatableField field);
050    }