Allow TestCompiler DynamicClassLoader to resolve '.class' resources

Update `DynamicClassLoader` so that `findResource(...)` also considered
compiled class bytecode.

Closes gh-29347

Author: philwebb

spring-core-test/src/main/java/org/springframework/core/test/tools/DynamicClassLoader.java

@@ -31,6 +31,7 @@
 
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
 import org.springframework.util.ReflectionUtils;
 
 /**
@@ -91,15 +92,7 @@ protected Class<?> findClass(String name) throws ClassNotFoundException {
 		return super.findClass(name);
 	}
 
-	@Nullable
-	private byte[] findClassBytes(String name) {
-		ClassFile classFile = this.classFiles.get(name);
-		if (classFile != null) {
-			return classFile.getContent();
-		}
-		DynamicClassFileObject dynamicClassFile = this.dynamicClassFiles.get(name);
-		return (dynamicClassFile != null) ? dynamicClassFile.getBytes() : null;
-	}
+
 
 	private Class<?> defineClass(String name, byte[] bytes) {
 		if (this.defineClassMethod != null) {
@@ -109,7 +102,6 @@ private Class<?> defineClass(String name, byte[] bytes) {
 		return defineClass(name, bytes, 0, bytes.length);
 	}
 
-
 	@Override
 	protected Enumeration<URL> findResources(String name) throws IOException {
 		URL resource = findResource(name);
@@ -122,6 +114,14 @@ protected Enumeration<URL> findResources(String name) throws IOException {
 	@Override
 	@Nullable
 	protected URL findResource(String name) {
+		if (name.endsWith(ClassUtils.CLASS_FILE_SUFFIX)) {
+			String className = ClassUtils.convertResourcePathToClassName(name.substring(0,
+					name.length() - ClassUtils.CLASS_FILE_SUFFIX.length()));
+			byte[] classBytes = findClassBytes(className);
+			if (classBytes != null) {
+				return createResourceUrl(name, () -> classBytes);
+			}
+		}
 		ResourceFile resourceFile = this.resourceFiles.get(name);
 		if (resourceFile != null) {
 			return createResourceUrl(resourceFile.getPath(), resourceFile::getBytes);
@@ -133,6 +133,16 @@ protected URL findResource(String name) {
 		return super.findResource(name);
 	}
 
+	@Nullable
+	private byte[] findClassBytes(String name) {
+		ClassFile classFile = this.classFiles.get(name);
+		if (classFile != null) {
+			return classFile.getContent();
+		}
+		DynamicClassFileObject dynamicClassFile = this.dynamicClassFiles.get(name);
+		return (dynamicClassFile != null) ? dynamicClassFile.getBytes() : null;
+	}
+
 	private URL createResourceUrl(String name, Supplier<byte[]> bytesSupplier) {
 		try {
 			return new URL(null, "resource:///" + name,

spring-core-test/src/test/java/org/springframework/core/test/tools/TestCompilerTests.java

@@ -16,6 +16,7 @@
 
 package org.springframework.core.test.tools;
 
+import java.io.InputStream;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Set;
@@ -278,6 +279,15 @@ public String perform() {
 				compiled.getInstance(PublicInterface.class, "com.example.Test").perform()).isEqualTo("Hello from subpackage"));
 	}
 
+	@Test
+	void getResourceForCompiledBytecode() {
+		SourceFile sourceFile = SourceFile.of(HELLO_WORLD);
+		TestCompiler.forSystem().compile(sourceFile, compiled -> {
+			InputStream stream = compiled.getClassLoader().getResourceAsStream("com/example/Hello.class");
+			assertThat(stream).isNotNull();
+		});
+	}
+
 	private void assertSuppliesHelloWorld(Compiled compiled) {
 		assertThat(compiled.getInstance(Supplier.class).get()).isEqualTo("Hello World!");
 	}