Delete Devtools cache reset support for HATEOAS

As of spring-projects/spring-hateoas#854, Spring HATEOAS is not relying
on Objenesis anymore and removed the cache that was being used for it.

This commit removes the support for clearing that cache when running an
application with Devtools enabled.

See gh-16833

spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/autoconfigure/HateoasObjenesisCacheDisabler.java

-/*
- * Copyright 2012-2019 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.boot.devtools.autoconfigure;
-
-import java.lang.reflect.Field;
-
-import org.apache.commons.logging.Log;
-import org.apache.commons.logging.LogFactory;
-
-import org.springframework.beans.factory.InitializingBean;
-import org.springframework.util.ClassUtils;
-import org.springframework.util.ReflectionUtils;
-
-/**
- * Replaces the Objenesis instance in Spring HATEOAS's {@code DummyInvocationUtils} with
- * one that does not perform any caching. The cache is problematic as it's keyed on class
- * name which leads to {@code ClassCastExceptions} as the class loader changes across
- * restarts.
- *
- * @author Andy Wilkinson
- * @since 1.3.0
- */
-class HateoasObjenesisCacheDisabler implements InitializingBean {
-
-	private static final Log logger = LogFactory
-			.getLog(HateoasObjenesisCacheDisabler.class);
-
-	private static boolean cacheDisabled;
-
-	@Override
-	public void afterPropertiesSet() {
-		disableCaching();
-	}
-
-	private void disableCaching() {
-		if (!cacheDisabled) {
-			cacheDisabled = true;
-			doDisableCaching();
-		}
-	}
-
-	private void doDisableCaching() {
-		try {
-			Class<?> type = ClassUtils.forName(
-					"org.springframework.hateoas.server.core.DummyInvocationUtils",
-					getClass().getClassLoader());
-			removeObjenesisCache(type);
-		}
-		catch (Exception ex) {
-			// Assume that Spring HATEOAS is not on the classpath and continue
-		}
-	}
-
-	private void removeObjenesisCache(Class<?> dummyInvocationUtils) {
-		try {
-			Field objenesisField = ReflectionUtils.findField(dummyInvocationUtils,
-					"OBJENESIS");
-			if (objenesisField != null) {
-				ReflectionUtils.makeAccessible(objenesisField);
-				Object objenesis = ReflectionUtils.getField(objenesisField, null);
-				Field cacheField = ReflectionUtils.findField(objenesis.getClass(),
-						"cache");
-				ReflectionUtils.makeAccessible(cacheField);
-				ReflectionUtils.setField(cacheField, objenesis, null);
-			}
-		}
-		catch (Exception ex) {
-			logger.warn(
-					"Failed to disable Spring HATEOAS's Objenesis cache. ClassCastExceptions may occur",
-					ex);
-		}
-	}
-
-}

spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/autoconfigure/LocalDevToolsAutoConfiguration.java

@@ -133,11 +133,6 @@ public class LocalDevToolsAutoConfiguration {
 					this.properties.getRestart().getAllExclude());
 		}
 
-		@Bean
-		public HateoasObjenesisCacheDisabler hateoasObjenesisCacheDisabler() {
-			return new HateoasObjenesisCacheDisabler();
-		}
-
 		@Bean
 		public FileSystemWatcherFactory fileSystemWatcherFactory() {
 			return this::newFileSystemWatcher;

spring-boot-project/spring-boot-devtools/src/test/java/org/springframework/boot/devtools/autoconfigure/HateoasObjenesisCacheDisablerTests.java

-/*
- * Copyright 2012-2019 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.boot.devtools.autoconfigure;
-
-import java.util.concurrent.ConcurrentHashMap;
-
-import org.junit.After;
-import org.junit.Before;
-import org.junit.Test;
-
-import org.springframework.hateoas.server.core.DummyInvocationUtils;
-import org.springframework.objenesis.ObjenesisStd;
-import org.springframework.objenesis.instantiator.ObjectInstantiator;
-import org.springframework.test.util.ReflectionTestUtils;
-
-import static org.assertj.core.api.Assertions.assertThat;
-
-/**
- * Tests for {@link HateoasObjenesisCacheDisabler}.
- *
- * @author Andy Wilkinson
- */
-public class HateoasObjenesisCacheDisablerTests {
-
-	private ObjenesisStd objenesis;
-
-	@Before
-	@After
-	public void resetCacheField() {
-		ReflectionTestUtils.setField(HateoasObjenesisCacheDisabler.class, "cacheDisabled",
-				false);
-		this.objenesis = (ObjenesisStd) ReflectionTestUtils
-				.getField(DummyInvocationUtils.class, "OBJENESIS");
-		ReflectionTestUtils.setField(this.objenesis, "cache",
-				new ConcurrentHashMap<String, ObjectInstantiator<?>>());
-	}
-
-	@Test
-	public void cacheIsEnabledByDefault() {
-		assertThat(this.objenesis.getInstantiatorOf(TestObject.class))
-				.isSameAs(this.objenesis.getInstantiatorOf(TestObject.class));
-	}
-
-	@Test
-	public void cacheIsDisabled() {
-		new HateoasObjenesisCacheDisabler().afterPropertiesSet();
-		assertThat(this.objenesis.getInstantiatorOf(TestObject.class))
-				.isNotSameAs(this.objenesis.getInstantiatorOf(TestObject.class));
-	}
-
-	private static class TestObject {
-
-	}
-
-}