Revise TargetSource implementations for proper nullability

Includes hashCode optimization in AbstractBeanFactoryBasedTargetSource.
Includes ThreadLocal naming fix in ThreadLocalTargetSource.

Closes gh-30576
Closes gh-30581

(cherry picked from commit c685525)

Author: jhoeller

spring-aop/src/main/java/org/springframework/aop/framework/autoproxy/target/AbstractBeanFactoryBasedTargetSourceCreator.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -34,6 +34,7 @@
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 import org.springframework.beans.factory.support.GenericBeanDefinition;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 
 /**
  * Convenient superclass for
@@ -81,6 +82,11 @@ protected final BeanFactory getBeanFactory() {
 		return this.beanFactory;
 	}
 
+	private ConfigurableBeanFactory getConfigurableBeanFactory() {
+		Assert.state(this.beanFactory != null, "BeanFactory not set");
+		return this.beanFactory;
+	}
+
 
 	//---------------------------------------------------------------------
 	// Implementation of the TargetSourceCreator interface
@@ -104,7 +110,7 @@ public final TargetSource getTargetSource(Class<?> beanClass, String beanName) {
 		// We need to override just this bean definition, as it may reference other beans
 		// and we're happy to take the parent's definition for those.
 		// Always use prototype scope if demanded.
-		BeanDefinition bd = this.beanFactory.getMergedBeanDefinition(beanName);
+		BeanDefinition bd = getConfigurableBeanFactory().getMergedBeanDefinition(beanName);
 		GenericBeanDefinition bdCopy = new GenericBeanDefinition(bd);
 		if (isPrototypeBased()) {
 			bdCopy.setScope(BeanDefinition.SCOPE_PROTOTYPE);
@@ -126,7 +132,7 @@ public final TargetSource getTargetSource(Class<?> beanClass, String beanName) {
 	protected DefaultListableBeanFactory getInternalBeanFactoryForBean(String beanName) {
 		synchronized (this.internalBeanFactories) {
 			return this.internalBeanFactories.computeIfAbsent(beanName,
-					name -> buildInternalBeanFactory(this.beanFactory));
+					name -> buildInternalBeanFactory(getConfigurableBeanFactory()));
 		}
 	}
 

spring-aop/src/main/java/org/springframework/aop/target/AbstractBeanFactoryBasedTargetSource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2023 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 +24,8 @@
 import org.springframework.aop.TargetSource;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -57,15 +59,18 @@ public abstract class AbstractBeanFactoryBasedTargetSource implements TargetSour
 	protected final Log logger = LogFactory.getLog(getClass());
 
 	/** Name of the target bean we will create on each invocation. */
+	@Nullable
 	private String targetBeanName;
 
 	/** Class of the target. */
+	@Nullable
 	private volatile Class<?> targetClass;
 
 	/**
 	 * BeanFactory that owns this TargetSource. We need to hold onto this
 	 * reference so that we can create new prototype instances as necessary.
 	 */
+	@Nullable
 	private BeanFactory beanFactory;
 
 
@@ -86,6 +91,7 @@ public void setTargetBeanName(String targetBeanName) {
 	 * Return the name of the target bean in the factory.
 	 */
 	public String getTargetBeanName() {
+		Assert.state(this.targetBeanName != null, "Target bean name not set");
 		return this.targetBeanName;
 	}
 
@@ -115,11 +121,13 @@ public void setBeanFactory(BeanFactory beanFactory) {
 	 * Return the owning BeanFactory.
 	 */
 	public BeanFactory getBeanFactory() {
+		Assert.state(this.beanFactory != null, "BeanFactory not set");
 		return this.beanFactory;
 	}
 
 
 	@Override
+	@Nullable
 	public Class<?> getTargetClass() {
 		Class<?> targetClass = this.targetClass;
 		if (targetClass != null) {
@@ -128,7 +136,7 @@ public Class<?> getTargetClass() {
 		synchronized (this) {
 			// Full check within synchronization, entering the BeanFactory interaction algorithm only once...
 			targetClass = this.targetClass;
-			if (targetClass == null && this.beanFactory != null) {
+			if (targetClass == null && this.beanFactory != null && this.targetBeanName != null) {
 				// Determine type of the target bean.
 				targetClass = this.beanFactory.getType(this.targetBeanName);
 				if (targetClass == null) {
@@ -182,18 +190,16 @@ public boolean equals(Object other) {
 
 	@Override
 	public int hashCode() {
-		int hashCode = getClass().hashCode();
-		hashCode = 13 * hashCode + ObjectUtils.nullSafeHashCode(this.beanFactory);
-		hashCode = 13 * hashCode + ObjectUtils.nullSafeHashCode(this.targetBeanName);
-		return hashCode;
+		return getClass().hashCode() * 13 + ObjectUtils.nullSafeHashCode(this.targetBeanName);
 	}
 
 	@Override
 	public String toString() {
 		StringBuilder sb = new StringBuilder(getClass().getSimpleName());
 		sb.append(" for target bean '").append(this.targetBeanName).append('\'');
-		if (this.targetClass != null) {
-			sb.append(" of type [").append(this.targetClass.getName()).append(']');
+		Class<?> targetClass = this.targetClass;
+		if (targetClass != null) {
+			sb.append(" of type [").append(targetClass.getName()).append(']');
 		}
 		return sb.toString();
 	}

spring-aop/src/main/java/org/springframework/aop/target/AbstractLazyCreationTargetSource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -46,6 +46,7 @@ public abstract class AbstractLazyCreationTargetSource implements TargetSource {
 	protected final Log logger = LogFactory.getLog(getClass());
 
 	/** The lazily initialized target object. */
+	@Nullable
 	private Object lazyTarget;
 
 

spring-aop/src/main/java/org/springframework/aop/target/EmptyTargetSource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -70,6 +70,7 @@ public static EmptyTargetSource forClass(@Nullable Class<?> targetClass, boolean
 	// Instance implementation
 	//---------------------------------------------------------------------
 
+	@Nullable
 	private final Class<?> targetClass;
 
 	private final boolean isStatic;

spring-aop/src/main/java/org/springframework/aop/target/HotSwappableTargetSource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -95,8 +95,7 @@ public synchronized Object swap(Object newTarget) throws IllegalArgumentExceptio
 
 
 	/**
-	 * Two HotSwappableTargetSources are equal if the current target
-	 * objects are equal.
+	 * Two HotSwappableTargetSources are equal if the current target objects are equal.
 	 */
 	@Override
 	public boolean equals(Object other) {

spring-aop/src/main/java/org/springframework/aop/target/SingletonTargetSource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -82,14 +82,8 @@ public boolean isStatic() {
 	 */
 	@Override
 	public boolean equals(Object other) {
-		if (this == other) {
-			return true;
-		}
-		if (!(other instanceof SingletonTargetSource)) {
-			return false;
-		}
-		SingletonTargetSource otherTargetSource = (SingletonTargetSource) other;
-		return this.target.equals(otherTargetSource.target);
+		return (this == other || (other instanceof SingletonTargetSource &&
+				this.target.equals(((SingletonTargetSource) other).target)));
 	}
 
 	/**

spring-aop/src/main/java/org/springframework/aop/target/ThreadLocalTargetSource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -58,7 +58,12 @@ public class ThreadLocalTargetSource extends AbstractPrototypeBasedTargetSource
 	 * is meant to be per thread per instance of the ThreadLocalTargetSource class.
 	 */
 	private final ThreadLocal<Object> targetInThread =
-			new NamedThreadLocal<>("Thread-local instance of bean '" + getTargetBeanName() + "'");
+			new NamedThreadLocal<Object>("Thread-local instance of bean") {
+				@Override
+				public String toString() {
+					return super.toString() + " '" + getTargetBeanName() + "'";
+				}
+			};
 
 	/**
 	 * Set of managed targets, enabling us to keep track of the targets we've created.