Collect nested generic arguments when resolving type signatures

src/main/java/org/springframework/data/util/TypeUtils.java

@@ -22,6 +22,7 @@
 import java.lang.reflect.Method;
 import java.lang.reflect.Parameter;
 import java.util.Collection;
+import java.util.HashSet;
 import java.util.LinkedHashSet;
 import java.util.Set;
 import java.util.stream.Stream;
@@ -37,6 +38,7 @@
 
 /**
  * @author Christoph Strobl
+ * @author arimu1
  */
 // TODO: Consider moving to the org.springframework.data.util package or make this package-private if not used somewhere
 // else.
@@ -159,21 +161,25 @@ public static Set<Class<?>> resolveTypesInSignature(ResolvableType root) {
 	}
 
 	private static void resolveTypesInSignature(ResolvableType current, Set<Class<?>> signatures) {
+		resolveTypesInSignature(current, signatures, new HashSet<>());
+	}
+
+	private static void resolveTypesInSignature(ResolvableType current, Set<Class<?>> signatures, Set<String> visited) {
 
 		if (ResolvableType.NONE.equals(current) || ObjectUtils.nullSafeEquals(Void.TYPE, current.getType())
 				|| ObjectUtils.nullSafeEquals(Object.class, current.getType())) {
 			return;
 		}
-		if (signatures.contains(current.toClass())) {
+		if (!visited.add(current.toString())) {
 			return;
 		}
 		signatures.add(current.toClass());
-		resolveTypesInSignature(current.getSuperType(), signatures);
+		resolveTypesInSignature(current.getSuperType(), signatures, visited);
 		for (ResolvableType type : current.getGenerics()) {
-			resolveTypesInSignature(type, signatures);
+			resolveTypesInSignature(type, signatures, visited);
 		}
 		for (ResolvableType type : current.getInterfaces()) {
-			resolveTypesInSignature(type, signatures);
+			resolveTypesInSignature(type, signatures, visited);
 		}
 	}
 

src/test/java/org/springframework/data/aot/TypeCollectorUnitTests.java

@@ -29,6 +29,7 @@
  *
  * @author Christoph Strobl
  * @author Mark Paluch
+ * @author arimu1
  */
 public class TypeCollectorUnitTests {
 
@@ -99,4 +100,10 @@ void typeFilterReflectsAdditionalTypeFilters() {
 		assertThat(TypeCollector.inspect(c -> c.filterTypes(cls -> false), FieldsAndMethods.class).list()).isEmpty();
 	}
 
+	@Test // GH-3530
+	void detectsTypesNestedMoreThanOneGenericLevel() {
+		assertThat(TypeCollector.inspect(NestedGenericMaps.class).list()).contains(NestedGenericMaps.class,
+				EmptyType1.class, EmptyType2.class);
+	}
+
 }

src/test/java/org/springframework/data/aot/types/NestedGenericMaps.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2026 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
+ *
+ *      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.springframework.data.aot.types;
+
+import java.util.Map;
+
+/**
+ * @author arimu1
+ */
+public class NestedGenericMaps {
+
+	Map<String, EmptyType1> one;
+	Map<String, Map<String, EmptyType2>> two;
+}