Avoid shipping AWT classes in native images

This commit provides an alternative
java.beans.Introspector#findCustomizerClass implementation
via a GraalVM substitution that avoids to include thousands
of unused AWT classes in the native image.

Closes gh-29060

spring-core/graalvm/src/main/java/org/springframework/aot/graalvm/Target_ClassFinder.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2002-2022 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.graalvm;
+
+import com.oracle.svm.core.annotate.Alias;
+import com.oracle.svm.core.annotate.TargetClass;
+
+/**
+ * Allow to reference {@code com.sun.beans.finder.ClassFinder} from
+ * {@link Target_Introspector}.
+ *
+ * @author Sebastien Deleuze
+ * @since 6.0
+ */
+@TargetClass(className = "com.sun.beans.finder.ClassFinder")
+final class Target_ClassFinder {
+
+	@Alias
+	public static Class<?> findClass(String name, ClassLoader loader) throws ClassNotFoundException {
+		return null;
+	}
+}

spring-core/graalvm/src/main/java/org/springframework/aot/graalvm/Target_Introspector.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2002-2022 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.graalvm;
+
+import java.beans.Customizer;
+
+import com.oracle.svm.core.annotate.Substitute;
+import com.oracle.svm.core.annotate.TargetClass;
+
+/**
+ * {@link java.beans.Introspector} substitution with a refined {@code findCustomizerClass} implementation
+ * designed to avoid thousands of AWT classes to be included in the native image.
+ *
+ * @author Sebastien Deleuze
+ * @since 6.0
+ */
+@TargetClass(className = "java.beans.Introspector")
+final class Target_Introspector {
+
+	@Substitute
+	private static Class<?> findCustomizerClass(Class<?> type) {
+		String name = type.getName() + "Customizer";
+		try {
+			type = Target_ClassFinder.findClass(name, type.getClassLoader());
+			if (Customizer.class.isAssignableFrom(type)) {
+				Class<?> c = type;
+				do {
+					c = c.getSuperclass();
+					if (c.getName().equals("java.awt.Component")) {
+						return type;
+					}
+				} while (!c.getName().equals("java.lang.Object"));
+			}
+		}
+		catch (Exception exception) {
+		}
+		return null;
+	}
+
+}

src/checkstyle/checkstyle-suppressions.xml

@@ -37,6 +37,7 @@
 	<suppress files="SocketUtils" checks="HideUtilityClassConstructor"/>
 	<suppress files="ResolvableType" checks="FinalClass"/>
 	<suppress files="[\\/]src[\\/]testFixtures[\\/]java[\\/].+" checks="IllegalImport" id="bannedJUnitJupiterImports"/>
+	<suppress files="Target_ClassFinder" checks="HideUtilityClassConstructor"/>
 
 	<!-- spring-core-test -->
 	<suppress files="CompileWithTargetClassAccess" checks="IllegalImport" id="bannedJUnitJupiterImports" />