Improve documentation for BeanOverrideBeanFactoryPostProcessor

Author: sbrannen

spring-test/src/main/java/org/springframework/test/context/bean/override/BeanOverrideBeanFactoryPostProcessor.java

@@ -23,7 +23,6 @@
 
 import org.springframework.aop.scope.ScopedProxyUtils;
 import org.springframework.beans.BeansException;
-import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryUtils;
 import org.springframework.beans.factory.FactoryBean;
 import org.springframework.beans.factory.NoUniqueBeanDefinitionException;
@@ -44,7 +43,7 @@
 
 /**
  * A {@link BeanFactoryPostProcessor} implementation that processes identified
- * use of {@link BeanOverride @BeanOverride} and adapts the {@link BeanFactory}
+ * use of {@link BeanOverride @BeanOverride} and adapts the {@code BeanFactory}
  * accordingly.
  *
  * <p>For each override, the bean factory is prepared according to the chosen
@@ -119,17 +118,24 @@ private void replaceOrCreateBean(ConfigurableListableBeanFactory beanFactory, Be
 
 		// NOTE: This method supports 3 distinct scenarios which must be accounted for.
 		//
-		// 1) JVM runtime
-		// 2) AOT processing
-		// 3) AOT runtime
+		// - JVM runtime
+		// - AOT processing
+		// - AOT runtime
+		//
+		// In addition, this method supports 4 distinct use cases.
+		//
+		// 1) Override existing bean by-type
+		// 2) Create bean by-type, with a generated name
+		// 3) Override existing bean by-name
+		// 4) Create bean by-name, with a provided name
 
 		String beanName = handler.getBeanName();
 		Field field = handler.getField();
 		BeanDefinition existingBeanDefinition = null;
 		if (beanName == null) {
 			beanName = getBeanNameForType(beanFactory, handler, requireExistingBean);
 			if (beanName != null) {
-				// We are overriding an existing bean by-type.
+				// 1) We are overriding an existing bean by-type.
 				beanName = BeanFactoryUtils.transformedBeanName(beanName);
 				// If we are overriding a manually registered singleton, we won't find
 				// an existing bean definition.
@@ -138,15 +144,16 @@ private void replaceOrCreateBean(ConfigurableListableBeanFactory beanFactory, Be
 				}
 			}
 			else {
-				// We will later generate a name for the nonexistent bean, but since NullAway
-				// will reject leaving the beanName set to null, we set it to a placeholder.
+				// 2) We are creating a bean by-type, with a generated name.
+				// Since NullAway will reject leaving the beanName set to null,
+				// we set it to a placeholder that will be replaced later.
 				beanName = PSEUDO_BEAN_NAME_PLACEHOLDER;
 			}
 		}
 		else {
 			Set<String> candidates = getExistingBeanNamesByType(beanFactory, handler, false);
 			if (candidates.contains(beanName)) {
-				// We are overriding an existing bean by-name.
+				// 3) We are overriding an existing bean by-name.
 				existingBeanDefinition = beanFactory.getBeanDefinition(beanName);
 			}
 			else if (requireExistingBean) {
@@ -156,6 +163,7 @@ else if (requireExistingBean) {
 							.formatted(beanName, handler.getBeanType(),
 								field.getDeclaringClass().getSimpleName(), field.getName()));
 			}
+			// 4) We are creating a bean by-name with the provided beanName.
 		}
 
 		if (existingBeanDefinition != null) {
@@ -214,11 +222,14 @@ else if (Boolean.getBoolean(AbstractAotProcessor.AOT_PROCESSING)) {
 
 	/**
 	 * Check that a bean with the specified {@link BeanOverrideHandler#getBeanName() name}
-	 * and {@link BeanOverrideHandler#getBeanType() type} is registered.
-	 * <p>If so, put the {@link BeanOverrideHandler} in the early tracking map.
-	 * <p>The map will later be checked to see if a given bean should be wrapped
-	 * upon creation, during the {@link WrapEarlyBeanPostProcessor#getEarlyBeanReference}
-	 * phase.
+	 * or {@link BeanOverrideHandler#getBeanType() type} has already been registered
+	 * in the {@code BeanFactory}.
+	 * <p>If so, register the {@link BeanOverrideHandler} and the corresponding bean
+	 * name in the {@link BeanOverrideRegistry}.
+	 * <p>The registry will later be checked to see if a given bean should be wrapped
+	 * upon creation, during the early bean post-processing phase.
+	 * @see BeanOverrideRegistry#registerBeanOverrideHandler(BeanOverrideHandler, String)
+	 * @see WrapEarlyBeanPostProcessor#getEarlyBeanReference(Object, String)
 	 */
 	private void wrapBean(ConfigurableListableBeanFactory beanFactory, BeanOverrideHandler handler) {
 		String beanName = handler.getBeanName();
@@ -393,7 +404,7 @@ private static String determinePrimaryCandidate(
 	 * respectively.
 	 * <p>The returned bean definition should <strong>not</strong> be used to create
 	 * a bean instance but rather only for the purpose of having suitable bean
-	 * definition metadata available in the {@link BeanFactory} &mdash; for example,
+	 * definition metadata available in the {@code BeanFactory} &mdash; for example,
 	 * for autowiring candidate resolution.
 	 */
 	private static RootBeanDefinition createPseudoBeanDefinition(BeanOverrideHandler handler) {