/*
* Copyright 2002-2010 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.expression;
import org.springframework.core.convert.TypeDescriptor;
/**
* A type converter can convert values between different types encountered
* during expression evaluation. This is an SPI for the expression parser;
* see {@link org.springframework.core.convert.ConversionService} for the
* primary user API to Spring's conversion facilities.
*
* @author Andy Clement
* @author Juergen Hoeller
* @since 3.0
*/
public interface TypeConverter {
/**
* Return true if the type converter can convert the specified type to the desired target type.
* @param sourceType a type descriptor that describes the source type
* @param targetType a type descriptor that describes the requested result type
* @return true if that conversion can be performed
*/
boolean canConvert(TypeDescriptor sourceType, TypeDescriptor targetType);
/**
* Convert (may coerce) a value from one type to another, for example from a boolean to a string.
* The typeDescriptor parameter enables support for typed collections - if the caller really wishes they
* can have a List<Integer> for example, rather than simply a List.
* @param value the value to be converted
* @param sourceType a type descriptor that supplies extra information about the source object
* @param targetType a type descriptor that supplies extra information about the requested result type
* @return the converted value
* @throws EvaluationException if conversion is not possible
*/
Object convertValue(Object value, TypeDescriptor sourceType, TypeDescriptor targetType);
}
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