Throw ClassNotFoundException for missing class resource

ThrowawayClassLoader.loadClass fell back to loadClassFromResource,
which returns null when no class resource is available. Returning
null from loadClass violates the ClassLoader contract and leads to
a NullPointerException in callers such as PreComputeFieldFeature.

Re-throw the original ClassNotFoundException when the resource
fallback yields no class.

Signed-off-by: junhyeong9812 <pickjog@gmail.com>

Author: junhyeong9812

spring-core/src/main/java/org/springframework/aot/nativex/feature/ThrowawayClassLoader.java

@@ -54,7 +54,11 @@ protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundE
 				return super.loadClass(name, true);
 			}
 			catch (ClassNotFoundException ex) {
-				return loadClassFromResource(name);
+				Class<?> loadedFromResource = loadClassFromResource(name);
+				if (loadedFromResource == null) {
+					throw ex;
+				}
+				return loadedFromResource;
 			}
 		}
 	}

spring-core/src/test/java/org/springframework/aot/nativex/feature/ThrowawayClassLoaderTests.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2002-present 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.aot.nativex.feature;
+
+import java.io.InputStream;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+
+/**
+ * Tests for {@link ThrowawayClassLoader}.
+ *
+ * @author Junhyeong Kim
+ */
+class ThrowawayClassLoaderTests {
+
+	@Test
+	void loadClassThrowsClassNotFoundExceptionWhenClassResourceIsMissing() {
+		// The grandparent resolves bootstrap classes only, so super.loadClass(...) fails,
+		// and the resource loader provides no class bytes. The fallback must then honor the
+		// ClassLoader.loadClass contract by reporting the failure instead of returning null.
+		ClassLoader resourceLoader = new ClassLoader(new ClassLoader(null) {}) {
+			@Override
+			public InputStream getResourceAsStream(String name) {
+				return null;
+			}
+		};
+		ThrowawayClassLoader classLoader = new ThrowawayClassLoader(resourceLoader);
+
+		assertThatExceptionOfType(ClassNotFoundException.class)
+				.isThrownBy(() -> classLoader.loadClass("com.example.MissingClass"));
+	}
+
+}