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Support WildcardType resolution in GenericTypeResolver 

This commit adds support for WildcardType bounds resolution,
commonly seen in Kotlin due to declaration-site variance,
but also possible in Java even if less common.

Closes gh-22313
This commit is contained in:
Sébastien Deleuze 2023-06-30 11:41:03 +02:00
parent b8f091e2f6
commit f075120675
2 changed files with 101 additions and 18 deletions
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26
spring-core/src/main/java/org/springframework/core/GenericTypeResolver.java
View File

@ -39,6 +39,7 @@ import org.springframework.util.ConcurrentReferenceHashMap;
* @author Rob Harrop
* @author Sam Brannen
* @author Phillip Webb
* @author Sebastien Deleuze
* @since 2.5.2
*/
public final class GenericTypeResolver {
@ -166,7 +167,6 @@ public final class GenericTypeResolver {
}
else if (genericType instanceof ParameterizedType parameterizedType) {
ResolvableType resolvedType = ResolvableType.forType(genericType);
if (resolvedType.hasUnresolvableGenerics()) {
Class<?>[] generics = new Class<?>[parameterizedType.getActualTypeArguments().length];
Type[] typeArguments = parameterizedType.getActualTypeArguments();
ResolvableType contextType = ResolvableType.forClass(contextClass);
@ -181,6 +181,9 @@ public final class GenericTypeResolver {
generics[i] = ResolvableType.forType(typeArgument).resolve();
}
}
else if (typeArgument instanceof WildcardType wildcardType) {
generics[i] = resolveWildcard(wildcardType, contextType).resolve();
}
else {
generics[i] = ResolvableType.forType(typeArgument).resolve();
}
@ -191,7 +194,6 @@ public final class GenericTypeResolver {
}
}
}
}
return genericType;
}
@ -224,6 +226,26 @@ public final class GenericTypeResolver {
return ResolvableType.NONE;
}
private static ResolvableType resolveWildcard(WildcardType wildcardType, ResolvableType contextType) {
for (Type bound : wildcardType.getUpperBounds()) {
if (bound instanceof TypeVariable<?> typeVariable) {
ResolvableType resolvedTypeArgument = resolveVariable(typeVariable, contextType);
if (resolvedTypeArgument != ResolvableType.NONE) {
return resolvedTypeArgument;
}
}
}
for (Type bound : wildcardType.getLowerBounds()) {
if (bound instanceof TypeVariable<?> typeVariable) {
ResolvableType resolvedTypeArgument = resolveVariable(typeVariable, contextType);
if (resolvedTypeArgument != ResolvableType.NONE) {
return resolvedTypeArgument;
}
}
}
return ResolvableType.forType(wildcardType);
}
/**
* Resolve the specified generic type against the given TypeVariable map.
* <p>Used by Spring Data.

63
spring-core/src/test/java/org/springframework/core/GenericTypeResolverTests.java
View File

@ -1,5 +1,5 @@
/*
* Copyright 2002-2022 the original author or authors.
* Copyright 2002-2023 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.
@ -37,6 +37,7 @@ import static org.springframework.util.ReflectionUtils.findMethod;
/**
* @author Juergen Hoeller
* @author Sam Brannen
* @author Sebastien Deleuze
*/
@SuppressWarnings({"unchecked", "rawtypes"})
class GenericTypeResolverTests {
@ -185,6 +186,51 @@ class GenericTypeResolverTests {
assertThat(resolved).isEqualTo(E.class);
}
@Test
void resolveWildcardTypeWithUpperBound() {
Method method = findMethod(MySimpleSuperclassType.class, "upperBound", List.class);
Type resolved = resolveType(method.getGenericParameterTypes()[0], MySimpleSuperclassType.class);
ResolvableType resolvableType = ResolvableType.forType(resolved);
assertThat(resolvableType.hasUnresolvableGenerics()).isFalse();
assertThat(resolvableType.resolveGenerics()).containsExactly(String.class);
}
@Test
void resolveWildcardTypeWithUpperBoundWithResolvedType() {
Method method = findMethod(MySimpleSuperclassType.class, "upperBoundWithResolvedType", List.class);
Type resolved = resolveType(method.getGenericParameterTypes()[0], MySimpleSuperclassType.class);
ResolvableType resolvableType = ResolvableType.forType(resolved);
assertThat(resolvableType.hasUnresolvableGenerics()).isFalse();
assertThat(resolvableType.resolveGenerics()).containsExactly(Integer.class);
}
@Test
void resolveWildcardTypeWithLowerBound() {
Method method = findMethod(MySimpleSuperclassType.class, "lowerBound", List.class);
Type resolved = resolveType(method.getGenericParameterTypes()[0], MySimpleSuperclassType.class);
ResolvableType resolvableType = ResolvableType.forType(resolved);
assertThat(resolvableType.hasUnresolvableGenerics()).isFalse();
assertThat(resolvableType.resolveGenerics()).containsExactly(String.class);
}
@Test
void resolveWildcardTypeWithLowerBoundWithResolvedType() {
Method method = findMethod(MySimpleSuperclassType.class, "lowerBoundWithResolvedType", List.class);
Type resolved = resolveType(method.getGenericParameterTypes()[0], MySimpleSuperclassType.class);
ResolvableType resolvableType = ResolvableType.forType(resolved);
assertThat(resolvableType.hasUnresolvableGenerics()).isFalse();
assertThat(resolvableType.resolveGenerics()).containsExactly(Integer.class);
}
@Test
void resolveWildcardTypeWithUnbounded() {
Method method = findMethod(MySimpleSuperclassType.class, "unbounded", List.class);
Type resolved = resolveType(method.getGenericParameterTypes()[0], MySimpleSuperclassType.class);
ResolvableType resolvableType = ResolvableType.forType(resolved);
assertThat(resolvableType.hasUnresolvableGenerics()).isFalse();
assertThat(resolvableType.resolveGenerics()).containsExactly(Object.class);
}
public interface MyInterfaceType<T> {
}
@ -195,6 +241,21 @@ class GenericTypeResolverTests {
}
public abstract class MySuperclassType<T> {
public void upperBound(List<? extends T> list) {
}
public void upperBoundWithResolvedType(List<? extends Integer> list) {
}
public void lowerBound(List<? extends T> list) {
}
public void lowerBoundWithResolvedType(List<? super Integer> list) {
}
public void unbounded(List<?> list) {
}
}
public class MySimpleSuperclassType extends MySuperclassType<String> {