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.engine.IScriptSource;
020    import org.apache.tapestry.form.IFormComponent;
021    
022    /**
023     * An object that works with an {@link IFormComponent} to format output (convert object values to
024     * strings values) and to process input (convert strings to object values and validate them).
025     * <p>
026     * Note that this interface represents validation as supported in Tapestry 2.x to 3.0. It has been
027     * outdated (and will eventually be deprecated) by new support in Tapestry 4.0, centered around the
028     * {@link org.apache.tapestry.form.translator.Translator} and
029     * {@link org.apache.tapestry.form.validator.Validator} interfaces.
030     * 
031     * @author Howard Lewis Ship
032     * @since 1.0.8
033     */
034    
035    public interface IValidator
036    {
037        /**
038         * All validators must implement a required property. If true, the client must supply a non-null
039         * value.
040         */
041    
042        boolean isRequired();
043    
044        /**
045         * Invoked during rendering to convert an object value (which may be null) to a String. It is
046         * acceptible to return null. The string will be the VALUE attribute of the HTML text field.
047         */
048    
049        String toString(IFormComponent field, Object value);
050    
051        /**
052         * Converts input, submitted by the client, into an object value. May return null if the input
053         * is null (and the required flag is false).
054         * <p>
055         * The input string will already have been trimmed. It may be null.
056         * 
057         * @throws ValidatorException
058         *             if the string cannot be converted into an object, or the object is not valid (due
059         *             to other constraints).
060         */
061    
062        Object toObject(IFormComponent field, String input) throws ValidatorException;
063    
064        /**
065         * Invoked by the field after it finishes rendering its tag (but before the tag is closed) to
066         * allow the validator to provide a contribution to the rendering process. Validators typically
067         * generated client-side JavaScript to peform validation.
068         * 
069         * @since 2.2
070         */
071    
072        void renderValidatorContribution(IFormComponent field, IMarkupWriter writer,
073                IRequestCycle cycle);
074    
075        /**
076         * Sets the script source used to resolve script paths.
077         * 
078         * @param scriptSource
079         */
080        void setScriptSource(IScriptSource scriptSource);
081    }