Backport further refinements from the nullability efforts

Issue: SPR-15656

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -55,10 +55,10 @@
  * as String arrays are converted in such a format if the array itself is not
  * assignable.
  *
- * @author Rod Johnson
  * @author Juergen Hoeller
- * @author Rob Harrop
  * @author Stephane Nicoll
+ * @author Rod Johnson
+ * @author Rob Harrop
  * @since 4.2
  * @see #registerCustomEditor
  * @see #setPropertyValues
@@ -96,9 +96,7 @@ public abstract class AbstractNestablePropertyAccessor extends AbstractPropertyA
 
 	Object rootObject;
 
-	/**
-	 * Map with cached nested Accessors: nested path -> Accessor instance.
-	 */
+	/** Map with cached nested Accessors: nested path -> Accessor instance */
 	private Map<String, AbstractNestablePropertyAccessor> nestedPropertyAccessors;
 
 

spring-beans/src/main/java/org/springframework/beans/factory/CannotLoadBeanClassException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -46,8 +46,8 @@ public class CannotLoadBeanClassException extends FatalBeanException {
 	public CannotLoadBeanClassException(
 			String resourceDescription, String beanName, String beanClassName, ClassNotFoundException cause) {
 
-		super("Cannot find class [" + beanClassName + "] for bean with name '" + beanName +
-				"' defined in " + resourceDescription, cause);
+		super("Cannot find class [" + String.valueOf(beanClassName) + "] for bean with name '" + beanName + "'" +
+				(resourceDescription != null ? " defined in " + resourceDescription : ""), cause);
 		this.resourceDescription = resourceDescription;
 		this.beanName = beanName;
 		this.beanClassName = beanClassName;
@@ -64,8 +64,9 @@ public CannotLoadBeanClassException(
 	public CannotLoadBeanClassException(
 			String resourceDescription, String beanName, String beanClassName, LinkageError cause) {
 
-		super("Error loading class [" + beanClassName + "] for bean with name '" + beanName +
-				"' defined in " + resourceDescription + ": problem with class file or dependent class", cause);
+		super("Error loading class [" + String.valueOf(beanClassName) + "] for bean with name '" + beanName + "'" +
+				(resourceDescription != null ? " defined in " + resourceDescription : "") +
+				": problem with class file or dependent class", cause);
 		this.resourceDescription = resourceDescription;
 		this.beanName = beanName;
 		this.beanClassName = beanClassName;

spring-beans/src/main/java/org/springframework/beans/factory/config/DependencyDescriptor.java

@@ -240,12 +240,14 @@ public void setContainingClass(Class<?> containingClass) {
 	 * @since 4.0
 	 */
 	public ResolvableType getResolvableType() {
-		if (this.resolvableType == null) {
-			this.resolvableType = (this.field != null ?
+		ResolvableType resolvableType = this.resolvableType;
+		if (resolvableType == null) {
+			resolvableType = (this.field != null ?
 					ResolvableType.forField(this.field, this.nestingLevel, this.containingClass) :
 					ResolvableType.forMethodParameter(this.methodParameter));
+			this.resolvableType = resolvableType;
 		}
-		return this.resolvableType;
+		return resolvableType;
 	}
 
 	/**

spring-beans/src/main/java/org/springframework/beans/factory/support/StaticListableBeanFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -35,6 +35,7 @@
 import org.springframework.core.ResolvableType;
 import org.springframework.core.annotation.AnnotationUtils;
 import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
 /**
@@ -134,12 +135,21 @@ public Object getBean(String name) throws BeansException {
 	@SuppressWarnings("unchecked")
 	public <T> T getBean(String name, Class<T> requiredType) throws BeansException {
 		Object bean = getBean(name);
-		if (requiredType != null && !requiredType.isAssignableFrom(bean.getClass())) {
+		if (requiredType != null && !requiredType.isInstance(bean)) {
 			throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
 		}
 		return (T) bean;
 	}
 
+	@Override
+	public Object getBean(String name, Object... args) throws BeansException {
+		if (!ObjectUtils.isEmpty(args)) {
+			throw new UnsupportedOperationException(
+					"StaticListableBeanFactory does not support explicit bean creation arguments");
+		}
+		return getBean(name);
+	}
+
 	@Override
 	public <T> T getBean(Class<T> requiredType) throws BeansException {
 		String[] beanNames = getBeanNamesForType(requiredType);
@@ -154,18 +164,9 @@ else if (beanNames.length > 1) {
 		}
 	}
 
-	@Override
-	public Object getBean(String name, Object... args) throws BeansException {
-		if (args != null) {
-			throw new UnsupportedOperationException(
-					"StaticListableBeanFactory does not support explicit bean creation arguments");
-		}
-		return getBean(name);
-	}
-
 	@Override
 	public <T> T getBean(Class<T> requiredType, Object... args) throws BeansException {
-		if (args != null) {
+		if (!ObjectUtils.isEmpty(args)) {
 			throw new UnsupportedOperationException(
 					"StaticListableBeanFactory does not support explicit bean creation arguments");
 		}
@@ -352,7 +353,8 @@ public Map<String, Object> getBeansWithAnnotation(Class<? extends Annotation> an
 	public <A extends Annotation> A findAnnotationOnBean(String beanName, Class<A> annotationType)
 			throws NoSuchBeanDefinitionException{
 
-		return AnnotationUtils.findAnnotation(getType(beanName), annotationType);
+		Class<?> beanType = getType(beanName);
+		return (beanType != null ? AnnotationUtils.findAnnotation(beanType, annotationType) : null);
 	}
 
 }

spring-beans/src/main/java/org/springframework/beans/factory/xml/AbstractBeanDefinitionParser.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -140,7 +140,7 @@ protected void registerBeanDefinition(BeanDefinitionHolder definition, BeanDefin
 	/**
 	 * Central template method to actually parse the supplied {@link Element}
 	 * into one or more {@link BeanDefinition BeanDefinitions}.
-	 * @param element	the element that is to be parsed into one or more {@link BeanDefinition BeanDefinitions}
+	 * @param element the element that is to be parsed into one or more {@link BeanDefinition BeanDefinitions}
 	 * @param parserContext the object encapsulating the current state of the parsing process;
 	 * provides access to a {@link org.springframework.beans.factory.support.BeanDefinitionRegistry}
 	 * @return the primary {@link BeanDefinition} resulting from the parsing of the supplied {@link Element}

spring-beans/src/main/java/org/springframework/beans/factory/xml/BeanDefinitionParserDelegate.java

@@ -389,8 +389,7 @@ else if (parentDefaults != null) {
 	}
 
 	/**
-	 * Return the defaults definition object, or {@code null} if the
-	 * defaults have been initialized yet.
+	 * Return the defaults definition object.
 	 */
 	public DocumentDefaultsDefinition getDefaults() {
 		return this.defaults;

spring-context/src/main/java/org/springframework/context/annotation/ConditionContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -25,43 +25,39 @@
  * Context information for use by {@link Condition}s.
  *
  * @author Phillip Webb
+ * @author Juergen Hoeller
  * @since 4.0
  */
 public interface ConditionContext {
 
 	/**
 	 * Return the {@link BeanDefinitionRegistry} that will hold the bean definition
-	 * should the condition match or {@code null} if the registry is not available.
-	 * @return the registry or {@code null}
+	 * should the condition match, or {@code null} if the registry is not available.
 	 */
 	BeanDefinitionRegistry getRegistry();
 
 	/**
 	 * Return the {@link ConfigurableListableBeanFactory} that will hold the bean
-	 * definition should the condition match or {@code null} if the bean factory
+	 * definition should the condition match, or {@code null} if the bean factory
 	 * is not available.
-	 * @return the bean factory or {@code null}
 	 */
 	ConfigurableListableBeanFactory getBeanFactory();
 
 	/**
-	 * Return the {@link Environment} for which the current application is running
+	 * Return the {@link Environment} for which the current application is running,
 	 * or {@code null} if no environment is available.
-	 * @return the environment or {@code null}
 	 */
 	Environment getEnvironment();
 
 	/**
-	 * Return the {@link ResourceLoader} currently being used or {@code null}
-	 * if the resource loader cannot be obtained.
-	 * @return a resource loader or {@code null}
+	 * Return the {@link ResourceLoader} currently being used, or {@code null} if
+	 * the resource loader cannot be obtained.
 	 */
 	ResourceLoader getResourceLoader();
 
 	/**
-	 * Return the {@link ClassLoader} that should be used to load additional
-	 * classes or {@code null} if the default classloader should be used.
-	 * @return the class loader or {@code null}
+	 * Return the {@link ClassLoader} that should be used to load additional classes,
+	 * or {@code null} if the default classloader should be used.
 	 */
 	ClassLoader getClassLoader();
 

spring-context/src/test/java/org/springframework/jmx/IJmxTestBean.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -22,19 +22,19 @@
  */
 public interface IJmxTestBean {
 
-	public int add(int x, int y);
+	int add(int x, int y);
 
-	public long myOperation();
+	long myOperation();
 
-	public int getAge();
+	int getAge();
 
-	public void setAge(int age);
+	void setAge(int age);
 
-	public void setName(String name) throws Exception;
+	void setName(String name) throws Exception;
 
-	public String getName();
+	String getName();
 
 	// used to test invalid methods that exist in the proxy interface
-	public void dontExposeMe();
+	void dontExposeMe();
 
 }

spring-core/src/main/java/org/springframework/util/ClassUtils.java

@@ -1030,7 +1030,7 @@ public static String classPackageAsResourcePath(Class<?> clazz) {
 	 * in the given array.
 	 * <p>Basically like {@code AbstractCollection.toString()}, but stripping
 	 * the "class "/"interface " prefix before every class name.
-	 * @param classes a Collection of Class objects (may be {@code null})
+	 * @param classes an array of Class objects
 	 * @return a String of form "[com.foo.Bar, com.foo.Baz]"
 	 * @see java.util.AbstractCollection#toString()
 	 */
@@ -1231,6 +1231,7 @@ public static boolean isVisible(Class<?> clazz, ClassLoader classLoader) {
 	/**
 	 * Check whether the given object is a CGLIB proxy.
 	 * @param object the object to check
+	 * @see #isCglibProxyClass(Class)
 	 * @see org.springframework.aop.support.AopUtils#isCglibProxy(Object)
 	 */
 	public static boolean isCglibProxy(Object object) {
@@ -1240,6 +1241,7 @@ public static boolean isCglibProxy(Object object) {
 	/**
 	 * Check whether the specified class is a CGLIB-generated class.
 	 * @param clazz the class to check
+	 * @see #isCglibProxyClassName(String)
 	 */
 	public static boolean isCglibProxyClass(Class<?> clazz) {
 		return (clazz != null && isCglibProxyClassName(clazz.getName()));

spring-core/src/main/java/org/springframework/util/ConcurrentReferenceHashMap.java

@@ -419,9 +419,8 @@ protected final class Segment extends ReentrantLock {
 		private final int initialSize;
 
 		/**
-		 * Array of references indexed using the low order bits from the hash. This
-		 * property should only be set via {@link #setReferences} to ensure that the
-		 * {@code resizeThreshold} is maintained.
+		 * Array of references indexed using the low order bits from the hash.
+		 * This property should only be set along with {@code resizeThreshold}.
 		 */
 		private volatile Reference<K, V>[] references;
 
@@ -617,14 +616,14 @@ private void setReferences(Reference<K, V>[] references) {
 		}
 
 		/**
-		 * @return the size of the current references array
+		 * Return the size of the current references array.
 		 */
 		public final int getSize() {
 			return this.references.length;
 		}
 
 		/**
-		 * @return the total number of references in this segment
+		 * Return the total number of references in this segment.
 		 */
 		public final int getCount() {
 			return this.count;
@@ -639,21 +638,17 @@ public final int getCount() {
 	protected interface Reference<K, V> {
 
 		/**
-		 * Returns the referenced entry or {@code null} if the entry is no longer
-		 * available.
-		 * @return the entry or {@code null}
+		 * Return the referenced entry, or {@code null} if the entry is no longer available.
 		 */
 		Entry<K, V> get();
 
 		/**
-		 * Returns the hash for the reference.
-		 * @return the hash
+		 * Return the hash for the reference.
 		 */
 		int getHash();
 
 		/**
-		 * Returns the next reference in the chain or {@code null}
-		 * @return the next reference of {@code null}
+		 * Return the next reference in the chain, or {@code null} if none.
 		 */
 		Reference<K, V> getNext();
 
@@ -930,7 +925,7 @@ protected class ReferenceManager {
 		 * Factory method used to create a new {@link Reference}.
 		 * @param entry the entry contained in the reference
 		 * @param hash the hash
-		 * @param next the next reference in the chain or {@code null}
+		 * @param next the next reference in the chain, or {@code null} if none
 		 * @return a new {@link Reference}
 		 */
 		public Reference<K, V> createReference(Entry<K, V> entry, int hash, Reference<K, V> next) {