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GenericTypeResolver.resolveType should resolve TypeVariable with nested ParameterizedType #36480

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Merged
jhoeller merged 2 commits into from
Mar 21, 2026
+31 −0
Merged

GenericTypeResolver.resolveType should resolve TypeVariable with nested ParameterizedType #36480

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6df6b32
Add test case
anaconda875 Mar 16, 2026
66a057c
Fix GenericTypeResolver.resolveType should resolve TypeVariable with …
anaconda875 Mar 16, 2026
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4 changes: 4 additions & 0 deletions spring-core/src/main/java/org/springframework/core/GenericTypeResolver.java
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Original file line number Diff line number Diff line change
Expand Up @@ -160,6 +160,10 @@ public static Type resolveType(Type genericType, @Nullable Class<?> contextClass
resolvedTypeVariable = ResolvableType.forVariableBounds(typeVariable);
}
if (resolvedTypeVariable != ResolvableType.NONE) {
Type type = resolvedTypeVariable.getType();
if (type instanceof ParameterizedType) {
return resolveType(type, contextClass);
}
Class<?> resolved = resolvedTypeVariable.resolve();
if (resolved != null) {
return resolved;
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27 changes: 27 additions & 0 deletions spring-core/src/test/java/org/springframework/core/GenericTypeResolverTests.java
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.function.Supplier;

import org.junit.jupiter.api.Test;
Expand Down Expand Up @@ -250,6 +251,15 @@ void resolveTypeFromGenericDefaultMethod() {
assertThat(resolvedType).isEqualTo(InheritsDefaultMethod.ConcreteType.class);
}

@Test
void resolveTypeFromNestedParameterizedType() {
Type resolvedType = resolveType(method(MyInterfaceType.class, "get").getGenericReturnType(), MyCollectionInterfaceType.class);
assertThat(resolvedType).isEqualTo(method(MyCollectionInterfaceType.class, "get").getGenericReturnType());

resolvedType = resolveType(method(MyInterfaceType.class, "get").getGenericReturnType(), MyOptionalInterfaceType.class);
assertThat(resolvedType).isEqualTo(method(MyOptionalInterfaceType.class, "get").getGenericReturnType());
}

private static Method method(Class<?> target, String methodName, Class<?>... parameterTypes) {
Method method = findMethod(target, methodName, parameterTypes);
assertThat(method).describedAs(target.getName() + "#" + methodName).isNotNull();
Expand All @@ -258,12 +268,29 @@ private static Method method(Class<?> target, String methodName, Class<?>... par


public interface MyInterfaceType<T> {
default T get() {
return null;
}
}

public class MySimpleInterfaceType implements MyInterfaceType<String> {
}

public class MyParameterizedInterfaceType<P> implements MyInterfaceType<Collection<P>> {
}

public class MyOptionalInterfaceType extends MyParameterizedInterfaceType<Optional<String>> {
@Override
public Collection<Optional<String>> get() {
return super.get();
}
}

public class MyCollectionInterfaceType implements MyInterfaceType<Collection<String>> {
@Override
public Collection<String> get() {
return MyInterfaceType.super.get();
}
}

public abstract class MyAbstractType<T> implements MyInterfaceType<T> {
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