org.pkl.config.java.mapper.ConverterFactory Maven / Gradle / Ivy
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/*
* Copyright © 2024 Apple Inc. and the Pkl project authors. 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
*
* https://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.pkl.config.java.mapper;
import java.lang.reflect.Type;
import java.util.Optional;
import java.util.function.Predicate;
import org.pkl.core.PClassInfo;
/**
* A factory for {@link Converter}s. Used to implement conversions to generic Java classes. In such
* a case a single {@link Converter} does not suffice. Instead, the factory creates a new converter
* for every parameterization of the target type. Once created, the converter is cached for later
* use, and the factory is never again invoked for the same parameterized target type.
*
* For best performance, all introspection of target types (for example using {@link Reflection})
* should happen in the factory rather than the returned converters.
*/
@FunctionalInterface
public interface ConverterFactory {
/**
* Returns a converter for the given source and target types, or {@code Optional.empty()} if the
* factory cannot handle the requested types.
*/
// idea: return Success/Failure providing an explanation of why this factory wasn't applicable
Optional> create(PClassInfo sourceType, Type targetType);
/**
* Returns a new factory that restricts use of this factory to target types for which the given
* predicate holds.
*/
default ConverterFactory when(Predicate predicate) {
return (sourceType, targetType) -> {
if (!predicate.test(targetType)) return Optional.empty();
return create(sourceType, targetType);
};
}
}