Nullability refinements and related polishing

spring-beans/src/main/java/org/springframework/beans/TypeMismatchException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -41,10 +41,10 @@ public class TypeMismatchException extends PropertyAccessException {
 	private String propertyName;
 
 	@Nullable
-	private transient Object value;
+	private final transient Object value;
 
 	@Nullable
-	private Class<?> requiredType;
+	private final Class<?> requiredType;
 
 
 	/**

spring-context/src/main/java/org/springframework/validation/beanvalidation/LocalValidatorFactoryBean.java

@@ -294,7 +294,7 @@ public class LocalValidatorFactoryBean extends SpringValidatorAdapter
 		}
 		List<InputStream> mappingStreams = null;
 		if (this.mappingLocations != null) {
-			mappingStreams = new ArrayList<>(mappingLocations.length);
+			mappingStreams = new ArrayList<>(this.mappingLocations.length);
 			for (Resource location : this.mappingLocations) {
 				try {
 					InputStream stream = location.getInputStream();

spring-context/src/test/java/org/springframework/context/annotation/EnableLoadTimeWeavingTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -40,7 +40,7 @@ public class EnableLoadTimeWeavingTests {
 	@Test
 	public void control() {
 		GenericXmlApplicationContext ctx =
-			new GenericXmlApplicationContext(getClass(), "EnableLoadTimeWeavingTests-context.xml");
+				new GenericXmlApplicationContext(getClass(), "EnableLoadTimeWeavingTests-context.xml");
 		ctx.getBean("loadTimeWeaver", LoadTimeWeaver.class);
 	}
 
@@ -73,9 +73,11 @@ public class EnableLoadTimeWeavingTests {
 		verify(loadTimeWeaver).addTransformer(isA(ClassFileTransformer.class));
 	}
 
+
 	@Configuration
 	@EnableLoadTimeWeaving(aspectjWeaving=AspectJWeaving.DISABLED)
 	static class EnableLTWConfig_withAjWeavingDisabled implements LoadTimeWeavingConfigurer {
+
 		@Override
 		public LoadTimeWeaver getLoadTimeWeaver() {
 			return mock(LoadTimeWeaver.class);
@@ -85,6 +87,7 @@ public class EnableLoadTimeWeavingTests {
 	@Configuration
 	@EnableLoadTimeWeaving(aspectjWeaving=AspectJWeaving.AUTODETECT)
 	static class EnableLTWConfig_withAjWeavingAutodetect implements LoadTimeWeavingConfigurer {
+
 		@Override
 		public LoadTimeWeaver getLoadTimeWeaver() {
 			return mock(LoadTimeWeaver.class);
@@ -94,9 +97,11 @@ public class EnableLoadTimeWeavingTests {
 	@Configuration
 	@EnableLoadTimeWeaving(aspectjWeaving=AspectJWeaving.ENABLED)
 	static class EnableLTWConfig_withAjWeavingEnabled implements LoadTimeWeavingConfigurer {
+
 		@Override
 		public LoadTimeWeaver getLoadTimeWeaver() {
 			return mock(LoadTimeWeaver.class);
 		}
 	}
+
 }

spring-test/src/main/java/org/springframework/test/context/event/ApplicationEventsHolder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -67,7 +67,6 @@ public abstract class ApplicationEventsHolder {
 	 * @throws IllegalStateException if an instance of {@code ApplicationEvents}
 	 * has not been registered for the current thread
 	 */
-	@Nullable
 	public static ApplicationEvents getRequiredApplicationEvents() {
 		ApplicationEvents events = applicationEvents.get();
 		Assert.state(events != null, "Failed to retrieve ApplicationEvents for the current thread. " +

spring-web/src/main/java/org/springframework/http/client/reactive/JettyClientHttpResponse.java

@@ -32,6 +32,7 @@ import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseCookie;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.LinkedMultiValueMap;
@@ -147,10 +148,12 @@ class JettyClientHttpResponse implements ClientHttpResponse {
 			HttpHeaders headers = new HttpHeaders();
 			Iterable<?> iterator = (Iterable<?>)
 					ReflectionUtils.invokeMethod(getHeadersMethod, response.getResponse());
+			Assert.notNull(iterator, "Iterator must not be null");
 			for (Object field : iterator) {
-				headers.add(
+				String name = (String) ReflectionUtils.invokeMethod(getNameMethod, field);
-						(String) ReflectionUtils.invokeMethod(getNameMethod, field),
+				Assert.notNull(name, "Header name must not be null");
-						(String) ReflectionUtils.invokeMethod(getValueMethod, field));
+				String value = (String) ReflectionUtils.invokeMethod(getValueMethod, field);
+				headers.add(name, value);
 			}
 			return headers;
 		}

spring-web/src/main/java/org/springframework/http/converter/HttpMessageConverter.java

@@ -30,6 +30,7 @@ import org.springframework.lang.Nullable;
  *
  * @author Arjen Poutsma
  * @author Juergen Hoeller
+ * @author Rossen Stoyanchev
  * @since 3.0
  * @param <T> the converted object type
  */
@@ -67,8 +68,8 @@ public interface HttpMessageConverter<T> {
 	/**
 	 * Return the list of media types supported by this converter for the given
 	 * class. The list may differ from {@link #getSupportedMediaTypes()} if the
-	 * converter doesn't support given Class or if it support it only for a
+	 * converter does not support the given Class or if it supports it only for
-	 * subset of media types.
+	 * a subset of media types.
 	 * @param clazz the type of class to check
 	 * @return the list of media types supported for the given class
 	 * @since 5.3.4

spring-webflux/src/main/java/org/springframework/web/reactive/socket/server/upgrade/Jetty10RequestUpgradeStrategy.java

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.web.reactive.socket.server.upgrade;
 
 import java.lang.reflect.Method;
@@ -35,6 +36,7 @@ import org.springframework.http.server.reactive.ServerHttpResponse;
 import org.springframework.http.server.reactive.ServerHttpResponseDecorator;
 import org.springframework.lang.NonNull;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.util.ReflectionUtils;
 import org.springframework.web.reactive.socket.HandshakeInfo;
 import org.springframework.web.reactive.socket.WebSocketHandler;
@@ -67,7 +69,9 @@ public class Jetty10RequestUpgradeStrategy implements RequestUpgradeStrategy {
 
 			Class<?> type = loader.loadClass("org.eclipse.jetty.websocket.server.JettyWebSocketServerContainer");
 			getContainerMethod = type.getMethod("getContainer", ServletContext.class);
-			upgradeMethod = ReflectionUtils.findMethod(type, "upgrade", (Class<?>[]) null);
+			Method upgrade = ReflectionUtils.findMethod(type, "upgrade", (Class<?>[]) null);
+			Assert.state(upgrade != null, "Upgrade method not found");
+			upgradeMethod = upgrade;
 
 			type = loader.loadClass("org.eclipse.jetty.websocket.server.JettyServerUpgradeResponse");
 			setAcceptedSubProtocol = type.getMethod("setAcceptedSubProtocol", String.class);

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/AbstractMessageConverterMethodArgumentResolver.java

@@ -203,7 +203,8 @@ public abstract class AbstractMessageConverterMethodArgumentResolver implements
 					(noContentType && !message.hasBody())) {
 				return null;
 			}
-			throw new HttpMediaTypeNotSupportedException(contentType, getSupportedMediaTypes(targetClass));
+			throw new HttpMediaTypeNotSupportedException(contentType,
+					getSupportedMediaTypes(targetClass != null ? targetClass : Object.class));
 		}
 
 		MediaType selectedContentType = contentType;

spring-websocket/src/main/java/org/springframework/web/socket/server/jetty/Jetty10RequestUpgradeStrategy.java

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.web.socket.server.jetty;
 
 import java.lang.reflect.Method;
@@ -72,7 +73,9 @@ public class Jetty10RequestUpgradeStrategy implements RequestUpgradeStrategy {
 
 			Class<?> type = loader.loadClass("org.eclipse.jetty.websocket.server.JettyWebSocketServerContainer");
 			getContainerMethod = type.getMethod("getContainer", ServletContext.class);
-			upgradeMethod = ReflectionUtils.findMethod(type, "upgrade", (Class<?>[]) null);
+			Method upgrade = ReflectionUtils.findMethod(type, "upgrade", (Class<?>[]) null);
+			Assert.state(upgrade != null, "Upgrade method not found");
+			upgradeMethod = upgrade;
 
 			type = loader.loadClass("org.eclipse.jetty.websocket.server.JettyServerUpgradeResponse");
 			setAcceptedSubProtocol = type.getMethod("setAcceptedSubProtocol", String.class);