001/* 002 * Copyright 2002-2013 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.expression; 018 019import org.springframework.core.convert.TypeDescriptor; 020 021/** 022 * A type converter can convert values between different types encountered during 023 * expression evaluation. This is an SPI for the expression parser; see 024 * {@link org.springframework.core.convert.ConversionService} for the primary 025 * user API to Spring's conversion facilities. 026 * 027 * @author Andy Clement 028 * @author Juergen Hoeller 029 * @since 3.0 030 */ 031public interface TypeConverter { 032 033 /** 034 * Return {@code true} if the type converter can convert the specified type 035 * to the desired target type. 036 * @param sourceType a type descriptor that describes the source type 037 * @param targetType a type descriptor that describes the requested result type 038 * @return {@code true} if that conversion can be performed 039 */ 040 boolean canConvert(TypeDescriptor sourceType, TypeDescriptor targetType); 041 042 /** 043 * Convert (or coerce) a value from one type to another, for example from a 044 * {@code boolean} to a {@code String}. 045 * <p>The {@link TypeDescriptor} parameters enable support for typed collections: 046 * A caller may prefer a {@code List<Integer>}, for example, rather than 047 * simply any {@code List}. 048 * @param value the value to be converted 049 * @param sourceType a type descriptor that supplies extra information about the 050 * source object 051 * @param targetType a type descriptor that supplies extra information about the 052 * requested result type 053 * @return the converted value 054 * @throws EvaluationException if conversion failed or is not possible to begin with 055 */ 056 Object convertValue(Object value, TypeDescriptor sourceType, TypeDescriptor targetType); 057 058}