org.springframework.core.KotlinReflectionParameterNameDiscoverer Maven / Gradle / Ivy
/*
* Copyright 2002-2017 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.core;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.List;
import java.util.stream.Collectors;
import kotlin.reflect.KFunction;
import kotlin.reflect.KParameter;
import kotlin.reflect.jvm.ReflectJvmMapping;
import org.springframework.lang.Nullable;
/**
* {@link ParameterNameDiscoverer} implementation which uses Kotlin's reflection facilities
* for introspecting parameter names.
*
* Compared to {@link StandardReflectionParameterNameDiscoverer}, it allows in addition to
* determine interface parameter names without requiring Java 8 -parameters compiler flag.
*
* @author Sebastien Deleuze
* @since 5.0
*/
public class KotlinReflectionParameterNameDiscoverer implements ParameterNameDiscoverer {
@Override
@Nullable
public String[] getParameterNames(Method method) {
if (!KotlinDetector.isKotlinType(method.getDeclaringClass())) {
return null;
}
try {
KFunction function = ReflectJvmMapping.getKotlinFunction(method);
return (function != null ? getParameterNames(function.getParameters()) : null);
}
catch (UnsupportedOperationException ex) {
return null;
}
}
@Override
@Nullable
public String[] getParameterNames(Constructor ctor) {
if (!KotlinDetector.isKotlinType(ctor.getDeclaringClass())) {
return null;
}
try {
KFunction function = ReflectJvmMapping.getKotlinFunction(ctor);
return (function != null ? getParameterNames(function.getParameters()) : null);
}
catch (UnsupportedOperationException ex) {
return null;
}
}
@Nullable
private String[] getParameterNames(List parameters) {
List filteredParameters = parameters
.stream()
// Extension receivers of extension methods must be included as they appear as normal method parameters in Java
.filter(p -> KParameter.Kind.VALUE.equals(p.getKind()) || KParameter.Kind.EXTENSION_RECEIVER.equals(p.getKind()))
.collect(Collectors.toList());
String[] parameterNames = new String[filteredParameters.size()];
for (int i = 0; i < filteredParameters.size(); i++) {
KParameter parameter = filteredParameters.get(i);
// extension receivers are not explicitly named, but require a name for Java interoperability
// $receiver is not a valid Kotlin identifier, but valid in Java, so it can be used here
String name = KParameter.Kind.EXTENSION_RECEIVER.equals(parameter.getKind()) ? "$receiver" : parameter.getName();
if (name == null) {
return null;
}
parameterNames[i] = name;
}
return parameterNames;
}
}