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 015package org.apache.tapestry.form.validator; 016 017import org.apache.tapestry.form.IFormComponent; 018import org.apache.tapestry.form.FormComponentContributor; 019import org.apache.tapestry.form.ValidationMessages; 020import org.apache.tapestry.valid.ValidatorException; 021 022/** 023 * An object that can be "attached" to a {@link org.apache.tapestry.form.IFormComponent} to perform 024 * server-side validation ({@link #validate(IFormComponent, ValidationMessages, Object)}) as well 025 * as generate cleint-side validation (in the form of JavaScript submit listeners). 026 * 027 * @author Paul Ferraro 028 * @since 4.0 029 */ 030public interface Validator extends FormComponentContributor 031{ 032 /** 033 * Invoked to validate input for the field. A 034 * {@link org.apache.tapestry.form.translator.Translator} will have already converted the 035 * submitted user input string into an object. 036 * 037 * @param field 038 * the form element component being validated, often used to determine the 039 * {@link IFormComponent#getDisplayName() user presentable name} for the field, used 040 * in error messages. 041 * @param messages 042 * access to the pre-defined validation messages, in the appropriate locale 043 * @param object 044 * the client-side representation of the field's data. May be null if the client did 045 * not provide a value for the field (most Validators should check for null and 046 * perform no check if null). 047 * @throws ValidatorException 048 * if the object violates the constraint represented by this Validator. 049 */ 050 051 public void validate(IFormComponent field, ValidationMessages messages, Object object) 052 throws ValidatorException; 053 054 /** 055 * Returns true if this validator accepts null as the object parameter to validate(). When the 056 * object is null, validators that can't accept null are skipped. It is rare for a validator to 057 * return true. 058 */ 059 060 public boolean getAcceptsNull(); 061 062 /** 063 * Returns true if this field is required. Returns false otherwise. 064 */ 065 066 public boolean isRequired(); 067}