Avoid UndeclaredThrowableStrategy with 1.8 bytecode level (CGLIB 3.3)

ClassLoaderAwareUndeclaredThrowableStrategy fails with a VerifyError on recent JDKs after the CGLIB 3.3 upgrade. The alternative is to replace it with a plain ClassLoaderAwareGeneratorStrategy (extracted from CglibSubclassingInstantiationStrategy) and custom UndeclaredThrowableException handling in CglibMethodInvocation.

See gh-23453

spring-core/src/main/java/org/springframework/cglib/core/ClassLoaderAwareGeneratorStrategy.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2002-2019 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.cglib.core;
+
+/**
+ * CGLIB GeneratorStrategy variant which exposes the application ClassLoader
+ * as current thread context ClassLoader for the time of class generation.
+ * The ASM ClassWriter in Spring's ASM variant will pick it up when doing
+ * common superclass resolution.
+ *
+ * @author Juergen Hoeller
+ * @since 5.2
+ */
+public class ClassLoaderAwareGeneratorStrategy extends DefaultGeneratorStrategy {
+
+	private final ClassLoader classLoader;
+
+	public ClassLoaderAwareGeneratorStrategy(ClassLoader classLoader) {
+		this.classLoader = classLoader;
+	}
+
+	@Override
+	public byte[] generate(ClassGenerator cg) throws Exception {
+		if (this.classLoader == null) {
+			return super.generate(cg);
+		}
+
+		Thread currentThread = Thread.currentThread();
+		ClassLoader threadContextClassLoader;
+		try {
+			threadContextClassLoader = currentThread.getContextClassLoader();
+		}
+		catch (Throwable ex) {
+			// Cannot access thread context ClassLoader - falling back...
+			return super.generate(cg);
+		}
+
+		boolean overrideClassLoader = !this.classLoader.equals(threadContextClassLoader);
+		if (overrideClassLoader) {
+			currentThread.setContextClassLoader(this.classLoader);
+		}
+		try {
+			return super.generate(cg);
+		}
+		finally {
+			if (overrideClassLoader) {
+				// Reset original thread context ClassLoader.
+				currentThread.setContextClassLoader(threadContextClassLoader);
+			}
+		}
+	}
+
+}

spring-core/src/main/java/org/springframework/cglib/package-info.java

@@ -1,6 +1,6 @@
 /**
  * Spring's repackaging of
- * <a href="https://github.com/cglib/cglib">CGLIB 3.2</a>
+ * <a href="https://github.com/cglib/cglib">CGLIB 3.3</a>
  * (with Spring-specific patches; for internal use only).
  *
  * <p>This repackaging technique avoids any potential conflicts with