001    // Copyright 2004, 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.valid;
016    
017    import org.apache.tapestry.IMarkupWriter;
018    import org.apache.tapestry.IRequestCycle;
019    import org.apache.tapestry.form.IFormComponent;
020    
021    /**
022     * An object that works with an {@link IFormComponent} to format output (convert object values to
023     * strings values) and to process input (convert strings to object values and validate them).
024     * <p>
025     * Note that this interface represents validation as supported in Tapestry 2.x to 3.0. It has been
026     * outdated (and will eventually be deprecated) by new support in Tapestry 4.0, centered around the
027     * {@link org.apache.tapestry.form.translator.Translator} and
028     * {@link org.apache.tapestry.form.validator.Validator} interfaces.
029     * 
030     * @author Howard Lewis Ship
031     * @since 1.0.8
032     */
033    
034    public interface IValidator
035    {
036        /**
037         * All validators must implement a required property. If true, the client must supply a non-null
038         * value.
039         */
040    
041        public boolean isRequired();
042    
043        /**
044         * Invoked during rendering to convert an object value (which may be null) to a String. It is
045         * acceptible to return null. The string will be the VALUE attribute of the HTML text field.
046         */
047    
048        public String toString(IFormComponent field, Object value);
049    
050        /**
051         * Converts input, submitted by the client, into an object value. May return null if the input
052         * is null (and the required flag is false).
053         * <p>
054         * The input string will already have been trimmed. It may be null.
055         * 
056         * @throws ValidatorException
057         *             if the string cannot be converted into an object, or the object is not valid (due
058         *             to other constraints).
059         */
060    
061        public Object toObject(IFormComponent field, String input) throws ValidatorException;
062    
063        /**
064         * Invoked by the field after it finishes rendering its tag (but before the tag is closed) to
065         * allow the validator to provide a contribution to the rendering process. Validators typically
066         * generated client-side JavaScript to peform validation.
067         * 
068         * @since 2.2
069         */
070    
071        public void renderValidatorContribution(IFormComponent field, IMarkupWriter writer,
072                IRequestCycle cycle);
073    
074    }