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.validator;
016    
017    import java.util.List;
018    
019    import org.apache.tapestry.IComponent;
020    
021    /**
022     * Constructs {@link org.apache.tapestry.form.validator.Validator} instances from a specification. A
023     * specification is a comma-seperated list of entries. Each entry is in one of the following forms:
024     * <ul>
025     * <li><em>name</em>
026     * <li><em>name</em>=<em>value</em>
027     * <li><em>name[<em>message</em>]</em>
028     * <li><em>name</em>=<em>value</em>[<em>message</em>]
029     * <li>$<em>name</em>
030     * </ul>
031     * <p>
032     * Most validator classes are <em>configurable</em>: they have a property that matches their
033     * name. For example, {@link org.apache.tapestry.form.validator.MinDate} (which is named "minDate"
034     * has a <code>minDate</code> property. A few validators are not configurable ("required" =>
035     * {@link org.apache.tapestry.form.validator.Required}, for example).
036     * <p>
037     * Validators are expected to have a public no-args constructor. They are also expected to have a
038     * <code>message</code> property which is set from the value in brackets.
039     * The message is either a literal string, or may be prefixed with a '%' character, to indicate
040     * a localized key, resolved using the component's message catalog.
041     * <p>
042     * When the name is prefixed with a dollary sign, it indicates a reference to a <em>bean</em>
043     * with the given name.
044     * <p>
045     * A full validator specification might be:
046     * <code>required,email[%email-format],minLength=20[Email addresses must be at least 20 characters long.]
047     * 
048     * @author Howard Lewis Ship
049     * @since 4.0
050     */
051    public interface ValidatorFactory
052    {
053        /**
054         * Constructs a new (immutable) List of {@link Validator}, or returns a previously constructed
055         * List.
056         * 
057         * @param component
058         *            the component for which the list is being created
059         * @param specification
060         *            a string identifying which validators and their configuration
061         * @return List of {@link Validator} (possibly empty)
062         */
063        public List constructValidatorList(IComponent component, String specification);
064    }