Merge branch '3.5.x'

Closes gh-47899

Author: philwebb

core/spring-boot/src/main/java/org/springframework/boot/bootstrap/BootstrapContext.java

@@ -29,9 +29,14 @@
  * <p>
  * Provides lazy access to singletons that may be expensive to create, or need to be
  * shared before the {@link ApplicationContext} is available.
+ * <p>
+ * Instances are registered by type. The contact may return {@code null} values when a
+ * type has been registered but no value is actually supplied.
  *
  * @author Phillip Webb
  * @since 4.0.0
+ * @since 2.4.0
+ * @see BootstrapRegistry
  */
 public interface BootstrapContext {
 
@@ -40,7 +45,7 @@ public interface BootstrapContext {
 	 * will be created if it hasn't been accessed previously.
 	 * @param <T> the instance type
 	 * @param type the instance type
-	 * @return the instance managed by the context
+	 * @return the instance managed by the context, which may be {@code null}
 	 * @throws IllegalStateException if the type has not been registered
 	 */
 	<T> @Nullable T get(Class<T> type) throws IllegalStateException;
@@ -51,7 +56,7 @@ public interface BootstrapContext {
 	 * @param <T> the instance type
 	 * @param type the instance type
 	 * @param other the instance to use if the type has not been registered
-	 * @return the instance
+	 * @return the instance, which may be {@code null}
 	 */
 	<T> @Nullable T getOrElse(Class<T> type, @Nullable T other);
 
@@ -61,7 +66,7 @@ public interface BootstrapContext {
 	 * @param <T> the instance type
 	 * @param type the instance type
 	 * @param other a supplier for the instance to use if the type has not been registered
-	 * @return the instance
+	 * @return the instance, which may be {@code null}
 	 */
 	<T> @Nullable T getOrElseSupply(Class<T> type, Supplier<@Nullable T> other);
 
@@ -72,7 +77,7 @@ public interface BootstrapContext {
 	 * @param <X> the exception to throw if the type is not registered
 	 * @param type the instance type
 	 * @param exceptionSupplier the supplier which will return the exception to be thrown
-	 * @return the instance managed by the context
+	 * @return the instance managed by the context, which may be {@code null}
 	 * @throws X if the type has not been registered
 	 * @throws IllegalStateException if the type has not been registered
 	 */