src/main/java/org/osgi/util/converter/Functioning.java

/*
 * Copyright (c) OSGi Alliance (2017). All Rights Reserved.
 *
 * 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.osgi.util.converter;

import java.lang.reflect.Type;

import org.osgi.annotation.versioning.ProviderType;
import org.osgi.util.function.Function;

/**
 * This interface is used to specify the target function to perform conversions.
 * This function can be used multiple times. A {@link Functioning} instance can
 * be obtained via the {@link Converter}.
 *
 * @author $Id$
 */
@ProviderType
public interface Functioning extends Specifying<Functioning> {
	/**
	 * Specify the target object type for the conversion as a class object.
	 *
	 * @param cls The class to convert to.
	 * @param <T> The type to convert to.
	 * @return A function that can perform the conversion.
	 */
	<T> Function<Object,T> to(Class<T> cls);

	/**
	 * Specify the target object type as a Java Reflection Type object.
	 *
	 * @param type A Type object to represent the target type to be converted
	 *            to.
	 * @param <T> The type to convert to.
	 * @return A function that can perform the conversion.
	 */
	<T> Function<Object,T> to(Type type);

	/**
	 * Specify the target object type as a {@link TypeReference}. If the target
	 * class carries generics information a TypeReference should be used as this
	 * preserves the generic information whereas a Class object has this
	 * information erased. Example use:
	 *
	 * <pre>
	 * List&lt;String&gt; result = converter.function()
	 * 		.to(new TypeReference&lt;List&lt;String&gt;&gt;() {});
	 * </pre>
	 *
	 * @param ref A type reference to the object being converted to.
	 * @param <T> The type to convert to.
	 * @return A function that can perform the conversion.
	 */
	<T> Function<Object,T> to(TypeReference<T> ref);
}