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 015package org.apache.tapestry.coerce; 016 017/** 018 * Converts a value (possibly null) to an alternate data type; typically from String to boolean or a 019 * number type. 020 * <p> 021 * Typically, a ValueConverter will select a particular 022 * {@link org.apache.tapestry.coerce.TypeConverter}to perform the conversion. The 023 * {@link org.apache.tapestry.coerce.ValueConverterImpl}implementation also makes use of built-in 024 * {@link java.beans.PropertyEditor}s. 025 * 026 * @author Howard M. Lewis Ship 027 * @since 4.0 028 */ 029public interface ValueConverter 030{ 031 /** 032 * Performs a conversion of a value to a particular type. 033 * 034 * @param value 035 * The value to be converted (may be null) 036 * @param desiredType 037 * the type that will be converted to 038 * @returns the value converted to the indicated type. May return the input value if it is 039 * already assignable to the desiredType. 040 * @throws org.apache.hivemind.ApplicationRuntimeException 041 * if the value can not be converted 042 */ 043 public Object coerceValue(Object value, Class desiredType); 044}