Pass ClassLoader to Instantiator

Update `Instantiator` so that it can accept a `ClassLoader` when
creating instances and rework `EnvironmentPostProcessorsFactory` to
use the new methods.

Prior to this commit we would use the `ClassLoader` to get the class
names from `SpringFactories` but not when actually creating the
instances.

Fixes gh-27043

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/env/EnvironmentPostProcessorsFactory.java

 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -48,7 +48,7 @@ public interface EnvironmentPostProcessorsFactory {
 	 * @return an {@link EnvironmentPostProcessorsFactory} instance
 	 */
 	static EnvironmentPostProcessorsFactory fromSpringFactories(ClassLoader classLoader) {
-		return new ReflectionEnvironmentPostProcessorsFactory(
+		return new ReflectionEnvironmentPostProcessorsFactory(classLoader,
 				SpringFactoriesLoader.loadFactoryNames(EnvironmentPostProcessor.class, classLoader));
 	}
 
@@ -69,7 +69,19 @@ public interface EnvironmentPostProcessorsFactory {
 	 * @return an {@link EnvironmentPostProcessorsFactory} instance
 	 */
 	static EnvironmentPostProcessorsFactory of(String... classNames) {
-		return new ReflectionEnvironmentPostProcessorsFactory(classNames);
+		return of(null, classNames);
+	}
+
+	/**
+	 * Return a {@link EnvironmentPostProcessorsFactory} that reflectively creates post
+	 * processors from the given class names.
+	 * @param classLoader the source class loader
+	 * @param classNames the post processor class names
+	 * @return an {@link EnvironmentPostProcessorsFactory} instance
+	 * @since 2.4.8
+	 */
+	static EnvironmentPostProcessorsFactory of(ClassLoader classLoader, String... classNames) {
+		return new ReflectionEnvironmentPostProcessorsFactory(classLoader, classNames);
 	}
 
 }

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/env/ReflectionEnvironmentPostProcessorsFactory.java

 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -16,6 +16,7 @@
 
 package org.springframework.boot.env;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 
@@ -35,17 +36,24 @@ import org.springframework.boot.util.Instantiator;
  */
 class ReflectionEnvironmentPostProcessorsFactory implements EnvironmentPostProcessorsFactory {
 
+	private final List<Class<?>> classes;
+
+	private ClassLoader classLoader;
+
 	private final List<String> classNames;
 
 	ReflectionEnvironmentPostProcessorsFactory(Class<?>... classes) {
-		this(Arrays.stream(classes).map(Class::getName).toArray(String[]::new));
+		this.classes = new ArrayList<>(Arrays.asList(classes));
+		this.classNames = null;
 	}
 
-	ReflectionEnvironmentPostProcessorsFactory(String... classNames) {
-		this(Arrays.asList(classNames));
+	ReflectionEnvironmentPostProcessorsFactory(ClassLoader classLoader, String... classNames) {
+		this(classLoader, Arrays.asList(classNames));
 	}
 
-	ReflectionEnvironmentPostProcessorsFactory(List<String> classNames) {
+	ReflectionEnvironmentPostProcessorsFactory(ClassLoader classLoader, List<String> classNames) {
+		this.classes = null;
+		this.classLoader = classLoader;
 		this.classNames = classNames;
 	}
 
@@ -60,7 +68,8 @@ class ReflectionEnvironmentPostProcessorsFactory implements EnvironmentPostProce
 					parameters.add(BootstrapContext.class, bootstrapContext);
 					parameters.add(BootstrapRegistry.class, bootstrapContext);
 				});
-		return instantiator.instantiate(this.classNames);
+		return (this.classes != null) ? instantiator.instantiateTypes(this.classes)
+				: instantiator.instantiate(this.classLoader, this.classNames);
 	}
 
 }

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/util/Instantiator.java

 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -17,7 +17,6 @@
 package org.springframework.boot.util;
 
 import java.lang.reflect.Constructor;
-import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
@@ -27,6 +26,9 @@ import java.util.List;
 import java.util.Map;
 import java.util.function.Consumer;
 import java.util.function.Function;
+import java.util.function.Supplier;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import org.springframework.core.annotation.AnnotationAwareOrderComparator;
 import org.springframework.util.Assert;
@@ -85,22 +87,48 @@ public class Instantiator<T> {
 	 * @return a list of instantiated instances
 	 */
 	public List<T> instantiate(Collection<String> names) {
-		List<T> instances = new ArrayList<>(names.size());
-		for (String name : names) {
-			instances.add(instantiate(name));
-		}
+		return instantiate((ClassLoader) null, names);
+	}
+
+	/**
+	 * Instantiate the given set of class name, injecting constructor arguments as
+	 * necessary.
+	 * @param classLoader the source classloader
+	 * @param names the class names to instantiate
+	 * @return a list of instantiated instances
+	 * @since 2.4.8
+	 */
+	public List<T> instantiate(ClassLoader classLoader, Collection<String> names) {
+		Assert.notNull(names, "Names must not be null");
+		return instantiate(names.stream().map((name) -> TypeSupplier.forName(classLoader, name)));
+	}
+
+	/**
+	 * Instantiate the given set of classes, injecting constructor arguments as necessary.
+	 * @param types the types to instantiate
+	 * @return a list of instantiated instances
+	 * @since 2.4.8
+	 */
+	public List<T> instantiateTypes(Collection<Class<?>> types) {
+		Assert.notNull(types, "Types must not be null");
+		return instantiate(types.stream().map((type) -> TypeSupplier.forType(type)));
+	}
+
+	public List<T> instantiate(Stream<TypeSupplier> typeSuppliers) {
+		List<T> instances = typeSuppliers.map(this::instantiate).collect(Collectors.toList());
 		AnnotationAwareOrderComparator.sort(instances);
 		return Collections.unmodifiableList(instances);
 	}
 
-	private T instantiate(String name) {
+	private T instantiate(TypeSupplier typeSupplier) {
 		try {
-			Class<?> type = ClassUtils.forName(name, null);
+			Class<?> type = typeSupplier.get();
 			Assert.isAssignable(this.type, type);
 			return instantiate(type);
 		}
 		catch (Throwable ex) {
-			throw new IllegalArgumentException("Unable to instantiate " + this.type.getName() + " [" + name + "]", ex);
+			throw new IllegalArgumentException(
+					"Unable to instantiate " + this.type.getName() + " [" + typeSupplier.getName() + "]", ex);
 		}
 	}
 
@@ -160,4 +188,47 @@ public class Instantiator<T> {
 
 	}
 
+	/**
+	 * {@link Supplier} that provides a class type.
+	 */
+	private interface TypeSupplier {
+
+		String getName();
+
+		Class<?> get() throws ClassNotFoundException;
+
+		static TypeSupplier forName(ClassLoader classLoader, String name) {
+			return new TypeSupplier() {
+
+				@Override
+				public String getName() {
+					return name;
+				}
+
+				@Override
+				public Class<?> get() throws ClassNotFoundException {
+					return ClassUtils.forName(name, classLoader);
+				}
+
+			};
+		}
+
+		static TypeSupplier forType(Class<?> type) {
+			return new TypeSupplier() {
+
+				@Override
+				public String getName() {
+					return type.getName();
+				}
+
+				@Override
+				public Class<?> get() throws ClassNotFoundException {
+					return type;
+				}
+
+			};
+		}
+
+	}
+
 }

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/env/EnvironmentPostProcessorsFactoryTests.java

 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -24,6 +24,7 @@ import org.junit.jupiter.api.Test;
 import org.springframework.boot.DefaultBootstrapContext;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.logging.DeferredLogFactory;
+import org.springframework.core.OverridingClassLoader;
 import org.springframework.core.env.ConfigurableEnvironment;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -67,6 +68,25 @@ class EnvironmentPostProcessorsFactoryTests {
 		assertThat(processors.get(0)).isInstanceOf(TestEnvironmentPostProcessor.class);
 	}
 
+	@Test
+	void ofClassNamesWithClassLoaderReturnsFactory() {
+		OverridingClassLoader classLoader = new OverridingClassLoader(getClass().getClassLoader()) {
+
+			@Override
+			protected boolean isEligibleForOverriding(String className) {
+				return super.isEligibleForOverriding(className)
+						&& className.equals(TestEnvironmentPostProcessor.class.getName());
+			}
+
+		};
+		EnvironmentPostProcessorsFactory factory = EnvironmentPostProcessorsFactory.of(classLoader,
+				TestEnvironmentPostProcessor.class.getName());
+		List<EnvironmentPostProcessor> processors = factory.getEnvironmentPostProcessors(this.logFactory,
+				this.bootstrapContext);
+		assertThat(processors).hasSize(1);
+		assertThat(processors.get(0).getClass().getClassLoader()).isSameAs(classLoader);
+	}
+
 	static class TestEnvironmentPostProcessor implements EnvironmentPostProcessor {
 
 		TestEnvironmentPostProcessor(DeferredLogFactory logFactory) {

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/env/ReflectionEnvironmentPostProcessorsFactoryTests.java

 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -28,6 +28,7 @@ import org.springframework.boot.BootstrapRegistry;
 import org.springframework.boot.DefaultBootstrapContext;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.logging.DeferredLogFactory;
+import org.springframework.core.OverridingClassLoader;
 import org.springframework.core.env.ConfigurableEnvironment;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -53,49 +54,65 @@ class ReflectionEnvironmentPostProcessorsFactoryTests {
 
 	@Test
 	void createWithClassNamesArrayCreatesFactory() {
-		ReflectionEnvironmentPostProcessorsFactory factory = new ReflectionEnvironmentPostProcessorsFactory(
+		ReflectionEnvironmentPostProcessorsFactory factory = new ReflectionEnvironmentPostProcessorsFactory(null,
 				TestEnvironmentPostProcessor.class.getName());
 		assertThatFactory(factory).createsSinglePostProcessor(TestEnvironmentPostProcessor.class);
 	}
 
 	@Test
 	void createWithClassNamesListCreatesFactory() {
-		ReflectionEnvironmentPostProcessorsFactory factory = new ReflectionEnvironmentPostProcessorsFactory(
+		ReflectionEnvironmentPostProcessorsFactory factory = new ReflectionEnvironmentPostProcessorsFactory(null,
 				Arrays.asList(TestEnvironmentPostProcessor.class.getName()));
 		assertThatFactory(factory).createsSinglePostProcessor(TestEnvironmentPostProcessor.class);
 	}
 
+	@Test
+	void createWithClassNamesAndClassLoaderListCreatesFactory() {
+		OverridingClassLoader classLoader = new OverridingClassLoader(getClass().getClassLoader()) {
+
+			@Override
+			protected boolean isEligibleForOverriding(String className) {
+				return super.isEligibleForOverriding(className)
+						&& className.equals(TestEnvironmentPostProcessor.class.getName());
+			}
+
+		};
+		ReflectionEnvironmentPostProcessorsFactory factory = new ReflectionEnvironmentPostProcessorsFactory(classLoader,
+				Arrays.asList(TestEnvironmentPostProcessor.class.getName()));
+		assertThatFactory(factory).createsSinglePostProcessorWithClassLoader(classLoader);
+	}
+
 	@Test
 	void getEnvironmentPostProcessorsWhenHasDefaultConstructorCreatesPostProcessors() {
-		ReflectionEnvironmentPostProcessorsFactory factory = new ReflectionEnvironmentPostProcessorsFactory(
+		ReflectionEnvironmentPostProcessorsFactory factory = new ReflectionEnvironmentPostProcessorsFactory(null,
 				TestEnvironmentPostProcessor.class.getName());
 		assertThatFactory(factory).createsSinglePostProcessor(TestEnvironmentPostProcessor.class);
 	}
 
 	@Test
 	void getEnvironmentPostProcessorsWhenHasLogFactoryConstructorCreatesPostProcessors() {
-		ReflectionEnvironmentPostProcessorsFactory factory = new ReflectionEnvironmentPostProcessorsFactory(
+		ReflectionEnvironmentPostProcessorsFactory factory = new ReflectionEnvironmentPostProcessorsFactory(null,
 				TestLogFactoryEnvironmentPostProcessor.class.getName());
 		assertThatFactory(factory).createsSinglePostProcessor(TestLogFactoryEnvironmentPostProcessor.class);
 	}
 
 	@Test
 	void getEnvironmentPostProcessorsWhenHasLogConstructorCreatesPostProcessors() {
-		ReflectionEnvironmentPostProcessorsFactory factory = new ReflectionEnvironmentPostProcessorsFactory(
+		ReflectionEnvironmentPostProcessorsFactory factory = new ReflectionEnvironmentPostProcessorsFactory(null,
 				TestLogEnvironmentPostProcessor.class.getName());
 		assertThatFactory(factory).createsSinglePostProcessor(TestLogEnvironmentPostProcessor.class);
 	}
 
 	@Test
 	void getEnvironmentPostProcessorsWhenHasBootstrapRegistryConstructorCreatesPostProcessors() {
-		ReflectionEnvironmentPostProcessorsFactory factory = new ReflectionEnvironmentPostProcessorsFactory(
+		ReflectionEnvironmentPostProcessorsFactory factory = new ReflectionEnvironmentPostProcessorsFactory(null,
 				TestBootstrapRegistryEnvironmentPostProcessor.class.getName());
 		assertThatFactory(factory).createsSinglePostProcessor(TestBootstrapRegistryEnvironmentPostProcessor.class);
 	}
 
 	@Test
 	void getEnvironmentPostProcessorsWhenHasNoSuitableConstructorThrowsException() {
-		ReflectionEnvironmentPostProcessorsFactory factory = new ReflectionEnvironmentPostProcessorsFactory(
+		ReflectionEnvironmentPostProcessorsFactory factory = new ReflectionEnvironmentPostProcessorsFactory(null,
 				BadEnvironmentPostProcessor.class.getName());
 		assertThatIllegalArgumentException()
 				.isThrownBy(() -> factory.getEnvironmentPostProcessors(this.logFactory, this.bootstrapContext))
@@ -115,11 +132,21 @@ class ReflectionEnvironmentPostProcessorsFactoryTests {
 		}
 
 		void createsSinglePostProcessor(Class<?> expectedType) {
+			EnvironmentPostProcessor processor = getSingleProcessor();
+			assertThat(processor).isInstanceOf(expectedType);
+		}
+
+		void createsSinglePostProcessorWithClassLoader(OverridingClassLoader classLoader) {
+			EnvironmentPostProcessor processor = getSingleProcessor();
+			assertThat(processor.getClass().getClassLoader()).isSameAs(classLoader);
+		}
+
+		private EnvironmentPostProcessor getSingleProcessor() {
 			List<EnvironmentPostProcessor> processors = this.factory.getEnvironmentPostProcessors(
 					ReflectionEnvironmentPostProcessorsFactoryTests.this.logFactory,
 					ReflectionEnvironmentPostProcessorsFactoryTests.this.bootstrapContext);
 			assertThat(processors).hasSize(1);
-			assertThat(processors.get(0)).isInstanceOf(expectedType);
+			return processors.get(0);
 		}
 
 	}

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/util/InstantiatorTests.java

 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -23,6 +23,7 @@ import java.util.List;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.core.Ordered;
+import org.springframework.core.OverridingClassLoader;
 import org.springframework.core.annotation.Order;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -76,6 +77,29 @@ class InstantiatorTests {
 		assertThat(instance.getParamC()).isEqualTo(this.paramC);
 	}
 
+	@Test
+	void instantiateTypesCreatesInstance() {
+		WithDefaultConstructor instance = createInstantiator(WithDefaultConstructor.class)
+				.instantiateTypes(Collections.singleton(WithDefaultConstructor.class)).get(0);
+		assertThat(instance).isInstanceOf(WithDefaultConstructor.class);
+	}
+
+	@Test
+	void instantiateWithClassLoaderCreatesInstance() {
+		OverridingClassLoader classLoader = new OverridingClassLoader(getClass().getClassLoader()) {
+
+			@Override
+			protected boolean isEligibleForOverriding(String className) {
+				return super.isEligibleForOverriding(className)
+						&& className.equals(WithDefaultConstructorSubclass.class.getName());
+			}
+
+		};
+		WithDefaultConstructor instance = createInstantiator(WithDefaultConstructor.class)
+				.instantiate(classLoader, Collections.singleton(WithDefaultConstructorSubclass.class.getName())).get(0);
+		assertThat(instance.getClass().getClassLoader()).isSameAs(classLoader);
+	}
+
 	@Test
 	void createWhenWrongTypeThrowsException() {
 		assertThatIllegalArgumentException()
@@ -96,7 +120,7 @@ class InstantiatorTests {
 		});
 	}
 
-	static class WithDefaultConstructor {
+	static class WithDefaultConstructorSubclass extends WithDefaultConstructor {
 
 	}
 

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/util/WithDefaultConstructor.java

+/*
+ * Copyright 2012-2021 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.boot.util;
+
+/**
+ * Simple public class with a default constructor.
+ *
+ * @author Phillip Webb
+ */
+public class WithDefaultConstructor {
+
+}