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/*******************************************************************************
* Copyright (c) Contributors to the Eclipse Foundation
*
* 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.
*
* SPDX-License-Identifier: Apache-2.0
*******************************************************************************/
package org.osgi.util.converter;
import java.lang.reflect.Type;
import org.osgi.annotation.versioning.ConsumerType;
/**
* An functional interface with a convert method that is passed the original
* object and the target type to perform a custom conversion.
*
* This interface can also be used to register a custom error handler.
*
* @author $Id: 753819645ba2b4ea93b68cf467206fd23dd9da6d $
*/
@ConsumerType
public interface ConverterFunction {
/**
* Special object to indicate that a custom converter rule or error handler
* cannot handle the conversion.
*/
static final Object CANNOT_HANDLE = new Object();
/**
* Convert the object into the target type.
*
* @param obj The object to be converted. This object will never be
* {@code null} as the convert function will not be invoked for
* null values.
* @param targetType The target type.
* @return The conversion result or {@link #CANNOT_HANDLE} to indicate that
* the convert function cannot handle this conversion. In this case
* the next matching rule or parent converter will be given a
* opportunity to convert.
* @throws Exception the operation can throw an exception if the conversion
* can not be performed due to incompatible types.
*/
Object apply(Object obj, Type targetType) throws Exception;
}