Improve TestCompiler and allow lookup based class defines

Update the `TestCompiler` so that classes can be defined using
a `Lookup`. This update allows package-private classes to be
accessed without needing a quite so unusual classloader setup.

The `@CompileWithTargetClassAccess` should be added to any
test that needs to use `Lookup` based defines. The test will
run with a completed forked classloader so not to pollute the
main classloader.

This commit also adds some useful additional APIs.

See gh-28120

spring-core-test/spring-core-test.gradle

@@ -4,6 +4,9 @@ dependencies {
 	api(project(":spring-core"))
 	api("org.assertj:assertj-core")
 	api("com.thoughtworks.qdox:qdox")
+	compileOnly("org.junit.jupiter:junit-jupiter")
+	compileOnly("org.junit.platform:junit-platform-engine")
+	compileOnly("org.junit.platform:junit-platform-launcher")
 }
 
 tasks.withType(PublishToMavenRepository).configureEach {

spring-core-test/src/main/java/org/springframework/aot/test/generator/compile/CompilationException.java

@@ -16,6 +16,11 @@
 
 package org.springframework.aot.test.generator.compile;
 
+import org.springframework.aot.test.generator.file.ResourceFile;
+import org.springframework.aot.test.generator.file.ResourceFiles;
+import org.springframework.aot.test.generator.file.SourceFile;
+import org.springframework.aot.test.generator.file.SourceFiles;
+
 /**
  * Exception thrown when code cannot compile.
  *
@@ -25,8 +30,29 @@ package org.springframework.aot.test.generator.compile;
 @SuppressWarnings("serial")
 public class CompilationException extends RuntimeException {
 
-	CompilationException(String message) {
-		super(message);
+
+	CompilationException(String errors, SourceFiles sourceFiles, ResourceFiles resourceFiles) {
+		super(buildMessage(errors, sourceFiles, resourceFiles));
+	}
+
+
+	private static String buildMessage(String errors, SourceFiles sourceFiles,
+			ResourceFiles resourceFiles) {
+		StringBuilder message = new StringBuilder();
+		message.append("Unable to compile source\n\n");
+		message.append(errors);
+		message.append("\n\n");
+		for (SourceFile sourceFile : sourceFiles) {
+			message.append("---- source:   " + sourceFile.getPath() + "\n\n");
+			message.append(sourceFile.getContent());
+			message.append("\n\n");
+		}
+		for (ResourceFile resourceFile : resourceFiles) {
+			message.append("---- resource: " + resourceFile.getPath() + "\n\n");
+			message.append(resourceFile.getContent());
+			message.append("\n\n");
+		}
+		return message.toString();
 	}
 
 }

spring-core-test/src/main/java/org/springframework/aot/test/generator/compile/CompileWithTargetClassAccess.java

@@ -0,0 +1,56 @@
+/*
+ * 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.test.generator.compile;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.MethodHandles.Lookup;
+
+import org.junit.jupiter.api.extension.ExtendWith;
+
+/**
+ * Annotation that can be used on tests that need a {@link TestCompiler} with
+ * non-public access to a target class. Allows the compiler to use
+ * {@link MethodHandles#privateLookupIn} to {@link Lookup#defineClass define the
+ * class} without polluting the test {@link ClassLoader}.
+ *
+ * @author Phillip Webb
+ * @since 6.0
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ ElementType.TYPE, ElementType.METHOD })
+@Documented
+@ExtendWith(CompileWithTargetClassAccessExtension.class)
+public @interface CompileWithTargetClassAccess {
+
+	/**
+	 * The target class names.
+	 * @return the class name
+	 */
+	String[] classNames() default {};
+
+	/**
+	 * The target classes.
+	 * @return the classes
+	 */
+	Class<?>[] classes() default {};
+
+}

spring-core-test/src/main/java/org/springframework/aot/test/generator/compile/CompileWithTargetClassAccessClassLoader.java

@@ -0,0 +1,78 @@
+/*
+ * 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.test.generator.compile;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
+import java.util.Enumeration;
+
+/**
+ * {@link ClassLoader} implementation to support
+ * {@link CompileWithTargetClassAccess @CompileWithTargetClassAccess}.
+ *
+ * @author Phillip Webb
+ * @since 6.0
+ */
+final class CompileWithTargetClassAccessClassLoader extends ClassLoader {
+
+	private final ClassLoader testClassLoader;
+
+	private final String[] targetClasses;
+
+
+	public CompileWithTargetClassAccessClassLoader(ClassLoader testClassLoader,
+			String[] targetClasses) {
+		super(testClassLoader.getParent());
+		this.testClassLoader = testClassLoader;
+		this.targetClasses = targetClasses;
+	}
+
+
+	public String[] getTargetClasses() {
+		return this.targetClasses;
+	}
+
+	@Override
+	public Class<?> loadClass(String name) throws ClassNotFoundException {
+		if (name.startsWith("org.junit") || name.startsWith("org.hamcrest")) {
+			return Class.forName(name, false, this.testClassLoader);
+		}
+		return super.loadClass(name);
+	}
+
+	@Override
+	protected Class<?> findClass(String name) throws ClassNotFoundException {
+		String resourceName = name.replace(".", "/") + ".class";
+		InputStream stream = this.testClassLoader.getResourceAsStream(resourceName);
+		if (stream != null) {
+			try (stream) {
+				byte[] bytes = stream.readAllBytes();
+				return defineClass(name, bytes, 0, bytes.length, null);
+			}
+			catch (IOException ex) {
+			}
+		}
+		return super.findClass(name);
+	}
+
+	@Override
+	protected Enumeration<URL> findResources(String name) throws IOException {
+		return this.testClassLoader.getResources(name);
+	}
+
+}

spring-core-test/src/main/java/org/springframework/aot/test/generator/compile/CompileWithTargetClassAccessExtension.java

@@ -0,0 +1,197 @@
+/*
+ * 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.test.generator.compile;
+
+import java.lang.reflect.AnnotatedElement;
+import java.lang.reflect.Method;
+import java.util.Arrays;
+import java.util.LinkedHashSet;
+import java.util.Set;
+
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.jupiter.api.extension.InvocationInterceptor;
+import org.junit.jupiter.api.extension.ReflectiveInvocationContext;
+import org.junit.platform.engine.discovery.DiscoverySelectors;
+import org.junit.platform.launcher.Launcher;
+import org.junit.platform.launcher.LauncherDiscoveryRequest;
+import org.junit.platform.launcher.TestPlan;
+import org.junit.platform.launcher.core.LauncherDiscoveryRequestBuilder;
+import org.junit.platform.launcher.core.LauncherFactory;
+import org.junit.platform.launcher.listeners.SummaryGeneratingListener;
+import org.junit.platform.launcher.listeners.TestExecutionSummary;
+
+import org.springframework.core.annotation.MergedAnnotation;
+import org.springframework.core.annotation.MergedAnnotations;
+import org.springframework.util.Assert;
+import org.springframework.util.CollectionUtils;
+import org.springframework.util.ReflectionUtils;
+
+/**
+ * JUnit {@link InvocationInterceptor} to support
+ * {@link CompileWithTargetClassAccess @CompileWithTargetClassAccess}.
+ *
+ * @author Christoph Dreis
+ * @author Phillip Webb
+ * @since 6.0
+ */
+class CompileWithTargetClassAccessExtension implements InvocationInterceptor {
+
+	@Override
+	public void interceptBeforeAllMethod(Invocation<Void> invocation,
+			ReflectiveInvocationContext<Method> invocationContext,
+			ExtensionContext extensionContext) throws Throwable {
+
+		intercept(invocation, extensionContext);
+	}
+
+	@Override
+	public void interceptBeforeEachMethod(Invocation<Void> invocation,
+			ReflectiveInvocationContext<Method> invocationContext,
+			ExtensionContext extensionContext) throws Throwable {
+
+		intercept(invocation, extensionContext);
+	}
+
+	@Override
+	public void interceptAfterEachMethod(Invocation<Void> invocation,
+			ReflectiveInvocationContext<Method> invocationContext,
+			ExtensionContext extensionContext) throws Throwable {
+
+		intercept(invocation, extensionContext);
+	}
+
+	@Override
+	public void interceptAfterAllMethod(Invocation<Void> invocation,
+			ReflectiveInvocationContext<Method> invocationContext,
+			ExtensionContext extensionContext) throws Throwable {
+
+		intercept(invocation, extensionContext);
+	}
+
+	@Override
+	public void interceptTestMethod(Invocation<Void> invocation,
+			ReflectiveInvocationContext<Method> invocationContext,
+			ExtensionContext extensionContext) throws Throwable {
+
+		intercept(invocation, extensionContext,
+				() -> runTestWithModifiedClassPath(invocationContext, extensionContext));
+	}
+
+	private void intercept(Invocation<Void> invocation, ExtensionContext extensionContext)
+			throws Throwable {
+
+		intercept(invocation, extensionContext, Action.NONE);
+	}
+
+	private void intercept(Invocation<Void> invocation, ExtensionContext extensionContext,
+			Action action) throws Throwable {
+
+		if (isUsingForkedClassPathLoader(extensionContext)) {
+			invocation.proceed();
+			return;
+		}
+		invocation.skip();
+		action.run();
+	}
+
+	private boolean isUsingForkedClassPathLoader(ExtensionContext extensionContext) {
+		Class<?> testClass = extensionContext.getRequiredTestClass();
+		ClassLoader classLoader = testClass.getClassLoader();
+		return classLoader.getClass().getName()
+				.equals(CompileWithTargetClassAccessClassLoader.class.getName());
+	}
+
+	private void runTestWithModifiedClassPath(
+			ReflectiveInvocationContext<Method> invocationContext,
+			ExtensionContext extensionContext) throws Throwable {
+
+		Class<?> testClass = extensionContext.getRequiredTestClass();
+		Method testMethod = invocationContext.getExecutable();
+		String[] targetClasses = getTargetClasses(testClass, testMethod);
+		ClassLoader originalClassLoader = Thread.currentThread().getContextClassLoader();
+		ClassLoader forkedClassPathClassLoader = new CompileWithTargetClassAccessClassLoader(
+				testClass.getClassLoader(), targetClasses);
+		Thread.currentThread().setContextClassLoader(forkedClassPathClassLoader);
+		try {
+			runTest(forkedClassPathClassLoader, testClass.getName(), testMethod.getName());
+		}
+		finally {
+			Thread.currentThread().setContextClassLoader(originalClassLoader);
+		}
+	}
+
+	private String[] getTargetClasses(AnnotatedElement... elements) {
+		Set<String> targetClasses = new LinkedHashSet<>();
+		for (AnnotatedElement element : elements) {
+			MergedAnnotation<?> annotation = MergedAnnotations.from(element)
+					.get(CompileWithTargetClassAccess.class);
+			if (annotation.isPresent()) {
+				Arrays.stream(annotation.getStringArray("classNames")).forEach(targetClasses::add);
+				Arrays.stream(annotation.getClassArray("classes")).map(Class::getName).forEach(targetClasses::add);
+				if (element instanceof Class<?> clazz) {
+					targetClasses.add(clazz.getName());
+				}
+			}
+		}
+		return targetClasses.toArray(String[]::new);
+	}
+
+	private void runTest(ClassLoader classLoader, String testClassName,
+			String testMethodName) throws Throwable {
+
+		Class<?> testClass = classLoader.loadClass(testClassName);
+		Method testMethod = findMethod(testClass, testMethodName);
+		LauncherDiscoveryRequest request = LauncherDiscoveryRequestBuilder.request()
+				.selectors(DiscoverySelectors.selectMethod(testClass, testMethod))
+				.build();
+		Launcher launcher = LauncherFactory.create();
+		TestPlan testPlan = launcher.discover(request);
+		SummaryGeneratingListener listener = new SummaryGeneratingListener();
+		launcher.registerTestExecutionListeners(listener);
+		launcher.execute(testPlan);
+		TestExecutionSummary summary = listener.getSummary();
+		if (!CollectionUtils.isEmpty(summary.getFailures())) {
+			throw summary.getFailures().get(0).getException();
+		}
+	}
+
+	private Method findMethod(Class<?> testClass, String testMethodName) {
+		Method method = ReflectionUtils.findMethod(testClass, testMethodName);
+		if (method == null) {
+			Method[] methods = ReflectionUtils.getUniqueDeclaredMethods(testClass);
+			for (Method candidate : methods) {
+				if (candidate.getName().equals(testMethodName)) {
+					return candidate;
+				}
+			}
+		}
+		Assert.state(method != null, () -> "Unable to find " + testClass + "." + testMethodName);
+		return method;
+	}
+
+
+	interface Action {
+
+		static Action NONE = () -> {
+		};
+
+
+		void run() throws Throwable;
+
+	}
+
+}

spring-core-test/src/main/java/org/springframework/aot/test/generator/compile/Compiled.java

@@ -74,6 +74,28 @@ public class Compiled {
 		return this.sourceFiles.getSingle();
 	}
 
+	/**
+	 * Return the single matching source file that was compiled.
+	 * @param pattern the pattern used to find the file
+	 * @return the single source file
+	 * @throws IllegalStateException if the compiler wasn't passed exactly one
+	 * file
+	 */
+	public SourceFile getSourceFile(String pattern) {
+		return this.sourceFiles.getSingle(pattern);
+	}
+
+	/**
+	 * Return the single source file that was compiled in the given package.
+	 * @param packageName the package name to check
+	 * @return the single source file
+	 * @throws IllegalStateException if the compiler wasn't passed exactly one
+	 * file
+	 */
+	public SourceFile getSourceFileFromPackage(String packageName) {
+		return this.sourceFiles.getSingleFromPackage(packageName);
+	}
+
 	/**
 	 * Return all source files that were compiled.
 	 * @return the source files used by the compiler

spring-core-test/src/main/java/org/springframework/aot/test/generator/compile/DynamicClassLoader.java

@@ -23,7 +23,7 @@ import java.lang.System.Logger;
 import java.lang.System.Logger.Level;
 import java.lang.invoke.MethodHandles;
 import java.lang.invoke.MethodHandles.Lookup;
-import java.lang.reflect.Modifier;
+import java.lang.reflect.Method;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.net.URLConnection;
@@ -34,9 +34,9 @@ import java.util.Map;
 
 import org.springframework.aot.test.generator.file.ResourceFile;
 import org.springframework.aot.test.generator.file.ResourceFiles;
-import org.springframework.aot.test.generator.file.SourceFile;
-import org.springframework.aot.test.generator.file.SourceFiles;
 import org.springframework.lang.Nullable;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.ReflectionUtils;
 
 /**
  * {@link ClassLoader} used to expose dynamically generated content.
@@ -50,20 +50,15 @@ public class DynamicClassLoader extends ClassLoader {
 	private static final Logger logger = System.getLogger(DynamicClassLoader.class.getName());
 
 
-	private final SourceFiles sourceFiles;
-
 	private final ResourceFiles resourceFiles;
 
 	private final Map<String, DynamicClassFileObject> classFiles;
 
-	private final ClassLoader sourceLoader;
 
+	public DynamicClassLoader(ClassLoader parent, ResourceFiles resourceFiles,
+			Map<String, DynamicClassFileObject> classFiles) {
 
-	public DynamicClassLoader(ClassLoader sourceLoader, SourceFiles sourceFiles,
-			ResourceFiles resourceFiles, Map<String, DynamicClassFileObject> classFiles) {
-		super(sourceLoader.getParent());
-		this.sourceLoader = sourceLoader;
-		this.sourceFiles = sourceFiles;
+		super(parent);
 		this.resourceFiles = resourceFiles;
 		this.classFiles = classFiles;
 	}
@@ -75,42 +70,43 @@ public class DynamicClassLoader extends ClassLoader {
 		if (classFile != null) {
 			return defineClass(name, classFile);
 		}
-		try {
-			Class<?> fromSourceLoader = this.sourceLoader.loadClass(name);
-			if (Modifier.isPublic(fromSourceLoader.getModifiers())) {
-				return fromSourceLoader;
-			}
-		}
-		catch (Exception ex) {
-			// Continue
-		}
-		try (InputStream classStream = this.sourceLoader.getResourceAsStream(name.replace(".", "/") + ".class")) {
-			byte[] bytes = classStream.readAllBytes();
-			return defineClass(name, bytes, 0, bytes.length, null);
-		}
-		catch (IOException ex) {
-			throw new ClassNotFoundException(name);
-		}
+		return super.findClass(name);
 	}
 
 	private Class<?> defineClass(String name, DynamicClassFileObject classFile) {
 		byte[] bytes = classFile.getBytes();
-		SourceFile sourceFile = this.sourceFiles.get(name);
-		if (sourceFile != null && sourceFile.getTarget() != null) {
+		Class<?> targetClass = getTargetClass(name);
+		if (targetClass != null) {
 			try {
-				Lookup lookup = MethodHandles.privateLookupIn(sourceFile.getTarget(),
-						MethodHandles.lookup());
+				Lookup lookup = MethodHandles.privateLookupIn(targetClass, MethodHandles.lookup());
 				return lookup.defineClass(bytes);
 			}
 			catch (IllegalAccessException ex) {
-				logger.log(Level.WARNING,
-						"Unable to define class using MethodHandles Lookup, "
-								+ "only public methods and classes will be accessible");
+				logger.log(Level.WARNING, "Unable to define class using MethodHandles Lookup, "
+						+ "only public methods and classes will be accessible");
 			}
 		}
 		return defineClass(name, bytes, 0, bytes.length, null);
 	}
 
+	private Class<?> getTargetClass(String name) {
+		ClassLoader parentClassLoader = getParent();
+		if (parentClassLoader.getClass().getName()
+				.equals(CompileWithTargetClassAccessClassLoader.class.getName())) {
+			String packageName = ClassUtils.getPackageName(name);
+			Method method = ReflectionUtils.findMethod(parentClassLoader.getClass(), "getTargetClasses");
+			ReflectionUtils.makeAccessible(method);
+			String[] targetCasses = (String[]) ReflectionUtils.invokeMethod(method, parentClassLoader);
+			for (String targetClass : targetCasses) {
+				String targetPackageName = ClassUtils.getPackageName(targetClass);
+				if (targetPackageName.equals(packageName)) {
+					return ClassUtils.resolveClassName(targetClass, this);
+				}
+			}
+		}
+		return null;
+	}
+
 	@Override
 	protected Enumeration<URL> findResources(String name) throws IOException {
 		URL resource = findResource(name);

spring-core-test/src/main/java/org/springframework/aot/test/generator/compile/TestCompiler.java

@@ -16,6 +16,7 @@
 
 package org.springframework.aot.test.generator.compile;
 
+import java.io.PrintStream;
 import java.util.List;
 import java.util.Locale;
 import java.util.function.Consumer;
@@ -92,6 +93,16 @@ public final class TestCompiler {
 				this.sourceFiles.and(sourceFiles), this.resourceFiles);
 	}
 
+	/**
+	 * Return a new {@link TestCompiler} instance with addition source files.
+	 * @param sourceFiles the additional source files
+	 * @return a new {@link TestCompiler} instance
+	 */
+	public TestCompiler withSources(Iterable<SourceFile> sourceFiles) {
+		return new TestCompiler(this.classLoader, this.compiler,
+				this.sourceFiles.and(sourceFiles), this.resourceFiles);
+	}
+
 	/**
 	 * Return a new {@link TestCompiler} instance with addition source files.
 	 * @param sourceFiles the additional source files
@@ -112,6 +123,16 @@ public final class TestCompiler {
 				this.resourceFiles.and(resourceFiles));
 	}
 
+	/**
+	 * Return a new {@link TestCompiler} instance with addition source files.
+	 * @param resourceFiles the additional source files
+	 * @return a new {@link TestCompiler} instance
+	 */
+	public TestCompiler withResources(Iterable<ResourceFile> resourceFiles) {
+		return new TestCompiler(this.classLoader, this.compiler, this.sourceFiles,
+				this.resourceFiles.and(resourceFiles));
+	}
+
 	/**
 	 * Return a new {@link TestCompiler} instance with addition resource files.
 	 * @param resourceFiles the additional resource files
@@ -179,8 +200,11 @@ public final class TestCompiler {
 		ClassLoader previousClassLoader = Thread.currentThread().getContextClassLoader();
 		try {
 			Thread.currentThread().setContextClassLoader(dynamicClassLoader);
-			compiled.accept(new Compiled(dynamicClassLoader, this.sourceFiles,
-					this.resourceFiles));
+			compiled.accept(new Compiled(dynamicClassLoader, this.sourceFiles, this.resourceFiles));
+		}
+		catch (IllegalAccessError ex) {
+			throw new IllegalAccessError(ex.getMessage() + ". " +
+					"For non-public access ensure annotate your tests with @CompileWithTargetClassAccess");
 		}
 		finally {
 			Thread.currentThread().setContextClassLoader(previousClassLoader);
@@ -202,11 +226,30 @@ public final class TestCompiler {
 					null, compilationUnits);
 			boolean result = task.call();
 			if (!result || errors.hasReportedErrors()) {
-				throw new CompilationException("Unable to compile source" + errors);
+				throw new CompilationException(errors.toString(), this.sourceFiles, this.resourceFiles);
 			}
 		}
-		return new DynamicClassLoader(classLoaderToUse, this.sourceFiles,
-				this.resourceFiles, fileManager.getClassFiles());
+		return new DynamicClassLoader(classLoaderToUse, this.resourceFiles, fileManager.getClassFiles());
+	}
+
+	/**
+	 * Print the contents of the source and resource files to the specified
+	 * {@link PrintStream}.
+	 * @param printStream the destination print stream
+	 * @return this instance
+	 */
+	public TestCompiler printFiles(PrintStream printStream) {
+		for (SourceFile sourceFile : this.sourceFiles) {
+			printStream.append("---- source:   " + sourceFile.getPath() + "\n\n");
+			printStream.append(sourceFile.getContent());
+			printStream.append("\n\n");
+		}
+		for (ResourceFile resourceFile : this.resourceFiles) {
+			printStream.append("---- resource: " + resourceFile.getPath() + "\n\n");
+			printStream.append(resourceFile.getContent());
+			printStream.append("\n\n");
+		}
+		return this;
 	}
 
 

spring-core-test/src/main/java/org/springframework/aot/test/generator/file/DynamicFileAssert.java

@@ -44,6 +44,11 @@ public class DynamicFileAssert<A extends DynamicFileAssert<A, F>, F extends Dyna
 		return this.myself;
 	}
 
+	public A doesNotContain(CharSequence... values) {
+		assertThat(this.actual.getContent()).doesNotContain(values);
+		return this.myself;
+	}
+
 	public A isEqualTo(@Nullable Object expected) {
 		if (expected instanceof DynamicFile) {
 			return super.isEqualTo(expected);

spring-core-test/src/main/java/org/springframework/aot/test/generator/file/DynamicFiles.java

@@ -20,12 +20,13 @@ import java.util.Arrays;
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
+import java.util.List;
 import java.util.Map;
+import java.util.function.Predicate;
 import java.util.stream.Stream;
 
 import org.springframework.lang.Nullable;
 
-
 /**
  * Internal class used by {@link SourceFiles} and {@link ResourceFiles} to
  * manage {@link DynamicFile} instances.
@@ -54,6 +55,12 @@ final class DynamicFiles<F extends DynamicFile> implements Iterable<F> {
 		return (DynamicFiles<F>) NONE;
 	}
 
+	DynamicFiles<F> and(Iterable<F> files) {
+		Map<String, F> merged = new LinkedHashMap<>(this.files);
+		files.forEach(file -> merged.put(file.getPath(), file));
+		return new DynamicFiles<>(Collections.unmodifiableMap(merged));
+	}
+
 	DynamicFiles<F> and(F[] files) {
 		Map<String, F> merged = new LinkedHashMap<>(this.files);
 		Arrays.stream(files).forEach(file -> merged.put(file.getPath(), file));
@@ -85,10 +92,15 @@ final class DynamicFiles<F extends DynamicFile> implements Iterable<F> {
 	}
 
 	F getSingle() {
-		if (this.files.size() != 1) {
+		return getSingle(candidate -> true);
+	}
+
+	F getSingle(Predicate<F> filter) {
+		List<F> files = this.files.values().stream().filter(filter).toList();
+		if (files.size() != 1) {
 			throw new IllegalStateException("No single file available");
 		}
-		return this.files.values().iterator().next();
+		return files.iterator().next();
 	}
 
 	@Override

spring-core-test/src/main/java/org/springframework/aot/test/generator/file/ResourceFile.java

@@ -16,8 +16,15 @@
 
 package org.springframework.aot.test.generator.file;
 
+import java.io.InputStreamReader;
+import java.nio.charset.StandardCharsets;
+
 import org.assertj.core.api.AssertProvider;
 
+import org.springframework.core.io.InputStreamSource;
+import org.springframework.lang.Nullable;
+import org.springframework.util.FileCopyUtils;
+
 /**
  * {@link DynamicFile} that holds resource file content and provides
  * {@link ResourceFileAssert} support.
@@ -46,6 +53,20 @@ public final class ResourceFile extends DynamicFile
 		return new ResourceFile(path, charSequence.toString());
 	}
 
+	/**
+	 * Factory method to create a new {@link ResourceFile} from the given
+	 * {@link InputStreamSource}.
+	 * @param path the relative path of the file or {@code null} to have the
+	 * path deduced
+	 * @param inputStreamSource the source for the file
+	 * @return a {@link SourceFile} instance
+	 */
+	public static ResourceFile of(@Nullable String path,
+			InputStreamSource inputStreamSource) {
+		return of(path, appendable -> appendable.append(FileCopyUtils.copyToString(
+				new InputStreamReader(inputStreamSource.getInputStream(), StandardCharsets.UTF_8))));
+	}
+
 	/**
 	 * Factory method to create a new {@link SourceFile} from the given
 	 * {@link WritableContent}.

spring-core-test/src/main/java/org/springframework/aot/test/generator/file/ResourceFiles.java

@@ -21,7 +21,6 @@ import java.util.stream.Stream;
 
 import org.springframework.lang.Nullable;
 
-
 /**
  * An immutable collection of {@link ResourceFile} instances.
  *
@@ -62,11 +61,21 @@ public final class ResourceFiles implements Iterable<ResourceFile> {
 	/**
 	 * Return a new {@link ResourceFiles} instance that merges files from
 	 * another array of {@link ResourceFile} instances.
-	 * @param ResourceFiles the instances to merge
+	 * @param resourceFiles the instances to merge
 	 * @return a new {@link ResourceFiles} instance containing merged content
 	 */
-	public ResourceFiles and(ResourceFile... ResourceFiles) {
-		return new ResourceFiles(this.files.and(ResourceFiles));
+	public ResourceFiles and(ResourceFile... resourceFiles) {
+		return new ResourceFiles(this.files.and(resourceFiles));
+	}
+
+	/**
+	 * Return a new {@link ResourceFiles} instance that merges files from another iterable
+	 * of {@link ResourceFiles} instances.
+	 * @param resourceFiles the instances to merge
+	 * @return a new {@link ResourceFiles} instance containing merged content
+	 */
+	public ResourceFiles and(Iterable<ResourceFile> resourceFiles) {
+		return new ResourceFiles(this.files.and(resourceFiles));
 	}
 
 	/**

spring-core-test/src/main/java/org/springframework/aot/test/generator/file/SourceFile.java

@@ -16,7 +16,10 @@
 
 package org.springframework.aot.test.generator.file;
 
+import java.io.IOException;
+import java.io.InputStreamReader;
 import java.io.StringReader;
+import java.nio.charset.StandardCharsets;
 
 import com.thoughtworks.qdox.JavaProjectBuilder;
 import com.thoughtworks.qdox.model.JavaClass;
@@ -25,7 +28,9 @@ import com.thoughtworks.qdox.model.JavaSource;
 import org.assertj.core.api.AssertProvider;
 import org.assertj.core.util.Strings;
 
+import org.springframework.core.io.InputStreamSource;
 import org.springframework.lang.Nullable;
+import org.springframework.util.FileCopyUtils;
 
 /**
  * {@link DynamicFile} that holds Java source code and provides
@@ -59,7 +64,7 @@ public final class SourceFile extends DynamicFile
 	 * @return a {@link SourceFile} instance
 	 */
 	public static SourceFile of(CharSequence charSequence) {
-		return of(null, appendable -> appendable.append(charSequence));
+		return of(null, charSequence);
 	}
 
 	/**
@@ -74,6 +79,33 @@ public final class SourceFile extends DynamicFile
 		return of(path, appendable -> appendable.append(charSequence));
 	}
 
+	/**
+	 * Factory method to create a new {@link SourceFile} from the given
+	 * {@link InputStreamSource}.
+	 * @param inputStreamSource the source for the file
+	 * @return a {@link SourceFile} instance
+	 */
+	public static SourceFile of(InputStreamSource inputStreamSource) {
+		return of(null, inputStreamSource);
+	}
+
+	/**
+	 * Factory method to create a new {@link SourceFile} from the given
+	 * {@link InputStreamSource}.
+	 * @param path the relative path of the file or {@code null} to have the
+	 * path deduced
+	 * @param inputStreamSource the source for the file
+	 * @return a {@link SourceFile} instance
+	 */
+	public static SourceFile of(@Nullable String path, InputStreamSource inputStreamSource) {
+		return of(path, appendable -> appendable.append(copyToString(inputStreamSource)));
+	}
+
+	private static String copyToString(InputStreamSource inputStreamSource) throws IOException {
+		InputStreamReader reader = new InputStreamReader(inputStreamSource.getInputStream(), StandardCharsets.UTF_8);
+		return FileCopyUtils.copyToString(reader);
+	}
+
 	/**
 	 * Factory method to create a new {@link SourceFile} from the given
 	 * {@link WritableContent}.
@@ -134,15 +166,9 @@ public final class SourceFile extends DynamicFile
 	}
 
 	/**
-	 * Return the target class for this source file or {@code null}. The target
-	 * class can be used if private lookup access is required.
-	 * @return the target class
+	 * Return the class name of the source file.
+	 * @return the class name
 	 */
-	@Nullable
-	public Class<?> getTarget() {
-		return null; // Not yet supported
-	}
-
 	public String getClassName() {
 		return this.javaSource.getClasses().get(0).getFullyQualifiedName();
 	}

spring-core-test/src/main/java/org/springframework/aot/test/generator/file/SourceFiles.java

@@ -17,6 +17,8 @@
 package org.springframework.aot.test.generator.file;
 
 import java.util.Iterator;
+import java.util.Objects;
+import java.util.regex.Pattern;
 import java.util.stream.Stream;
 
 import org.springframework.lang.Nullable;
@@ -68,6 +70,16 @@ public final class SourceFiles implements Iterable<SourceFile> {
 		return new SourceFiles(this.files.and(sourceFiles));
 	}
 
+	/**
+	 * Return a new {@link SourceFiles} instance that merges files from another
+	 * array of {@link SourceFile} instances.
+	 * @param sourceFiles the instances to merge
+	 * @return a new {@link SourceFiles} instance containing merged content
+	 */
+	public SourceFiles and(Iterable<SourceFile> sourceFiles) {
+		return new SourceFiles(this.files.and(sourceFiles));
+	}
+
 	/**
 	 * Return a new {@link SourceFiles} instance that merges files from another
 	 * {@link SourceFiles} instance.
@@ -120,6 +132,32 @@ public final class SourceFiles implements Iterable<SourceFile> {
 		return this.files.getSingle();
 	}
 
+	/**
+	 * Return the single matching source file contained in the collection.
+	 * @return the single file
+	 * @throws IllegalStateException if the collection doesn't contain exactly
+	 * one file
+	 */
+	public SourceFile getSingle(String pattern) throws IllegalStateException {
+		return getSingle(Pattern.compile(pattern));
+	}
+
+	private SourceFile getSingle(Pattern pattern) {
+		return this.files.getSingle(
+				candidate -> pattern.matcher(candidate.getClassName()).matches());
+	}
+
+	/**
+	 * Return a single source file contained in the specified package.
+	 * @return the single file
+	 * @throws IllegalStateException if the collection doesn't contain exactly
+	 * one file
+	 */
+	public SourceFile getSingleFromPackage(String packageName) {
+		return this.files.getSingle(candidate -> Objects.equals(packageName,
+				candidate.getJavaSource().getPackageName()));
+	}
+
 	@Override
 	public boolean equals(Object obj) {
 		if (this == obj) {

spring-core-test/src/test/java/org/springframework/aot/test/generator/compile/CompilationExceptionTests.java

@@ -18,6 +18,9 @@ package org.springframework.aot.test.generator.compile;
 
 import org.junit.jupiter.api.Test;
 
+import org.springframework.aot.test.generator.file.ResourceFiles;
+import org.springframework.aot.test.generator.file.SourceFiles;
+
 import static org.assertj.core.api.Assertions.assertThat;
 
 
@@ -31,8 +34,8 @@ class CompilationExceptionTests {
 
 	@Test
 	void getMessageReturnsMessage() {
-		CompilationException exception = new CompilationException("message");
-		assertThat(exception).hasMessage("message");
+		CompilationException exception = new CompilationException("message", SourceFiles.none(), ResourceFiles.none());
+		assertThat(exception).hasMessageContaining("message");
 	}
 
 }

spring-core-test/src/test/java/org/springframework/aot/test/generator/compile/TestCompilerTests.java

@@ -26,6 +26,7 @@ import org.springframework.aot.test.generator.file.ResourceFiles;
 import org.springframework.aot.test.generator.file.SourceFile;
 import org.springframework.aot.test.generator.file.SourceFiles;
 import org.springframework.aot.test.generator.file.WritableContent;
+import org.springframework.util.ClassUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
@@ -170,7 +171,8 @@ class TestCompilerTests {
 	}
 
 	@Test
-	void compiledCodeCanAccessExistingPackagePrivateClass() {
+	@CompileWithTargetClassAccess(classNames = "com.example.PackagePrivate")
+	void compiledCodeCanAccessExistingPackagePrivateClassIfAnnotated() throws ClassNotFoundException, LinkageError {
 		SourceFiles sourceFiles = SourceFiles.of(SourceFile.of("""
 				package com.example;
 
@@ -187,6 +189,26 @@ class TestCompilerTests {
 				.isEqualTo("Hello from PackagePrivate"));
 	}
 
+	@Test
+	void compiledCodeCannotAccessExistingPackagePrivateClassIfNotAnnotated() {
+		SourceFiles sourceFiles = SourceFiles.of(SourceFile.of("""
+				package com.example;
+
+				public class Test implements PublicInterface {
+
+					public String perform() {
+						return new PackagePrivate().perform();
+					}
+
+				}
+				"""));
+		assertThatExceptionOfType(IllegalAccessError.class)
+				.isThrownBy(() -> TestCompiler.forSystem().compile(sourceFiles,
+						compiled -> compiled.getInstance(PublicInterface.class, "com.example.Test").perform()))
+				.withMessageContaining(ClassUtils.getShortName(CompileWithTargetClassAccess.class));
+	}
+
+
 	private void assertSuppliesHelloWorld(Compiled compiled) {
 		assertThat(compiled.getInstance(Supplier.class).get()).isEqualTo("Hello World!");
 	}

spring-orm/src/test/java/org/springframework/orm/jpa/support/PersistenceAnnotationBeanPostProcessorTests.java

@@ -32,6 +32,7 @@ import org.springframework.aot.generator.DefaultGeneratedTypeContext;
 import org.springframework.aot.generator.GeneratedType;
 import org.springframework.aot.hint.RuntimeHints;
 import org.springframework.aot.hint.TypeReference;
+import org.springframework.aot.test.generator.compile.CompileWithTargetClassAccess;
 import org.springframework.aot.test.generator.compile.TestCompiler;
 import org.springframework.aot.test.generator.file.SourceFile;
 import org.springframework.aot.test.generator.file.SourceFiles;
@@ -126,6 +127,7 @@ class PersistenceAnnotationBeanPostProcessorTests {
 	}
 
 	@Test
+	@CompileWithTargetClassAccess(classes = DefaultPersistenceUnitField.class)
 	void generateEntityManagerFactoryInjection() {
 		GenericApplicationContext context = new AnnotationConfigApplicationContext();
 		context.registerBeanDefinition("test", new RootBeanDefinition(DefaultPersistenceUnitField.class));

src/checkstyle/checkstyle-suppressions.xml

@@ -38,6 +38,9 @@
 	<suppress files="ResolvableType" checks="FinalClass"/>
 	<suppress files="[\\/]src[\\/]testFixtures[\\/]java[\\/].+" checks="IllegalImport" id="bannedJUnitJupiterImports"/>
 
+	<!-- spring-core-test -->
+	<suppress files="CompileWithTargetClassAccess" checks="IllegalImport" id="bannedJUnitJupiterImports" />
+
 	<!-- spring-expression -->
 	<suppress files="ExpressionException" checks="MutableException"/>
 	<suppress files="SpelMessage" checks="JavadocVariable|JavadocStyle"/>