HHH-17555 don't use getClass() inside entity equals()

documentation/src/main/asciidoc/introduction/Entities.adoc

@@ -1579,18 +1579,25 @@ class Book {
     @Basic(optional=false)
     String isbn;
 
+    String getIsbn() {
+        return isbn;
+    }
+
     ...
 
     @Override
     public boolean equals(Object other) {
-        return other instanceof Book
-            && ((Book) other).isbn.equals(isbn);
+        return other instanceof Book                   // check type with instanceof, not getClass()
+            && ((Book) other).getIsbn().equals(isbn);  // compare natural ids
     }
     @Override
     public int hashCode() {
-        return isbn.hashCode();
+        return isbn.hashCode();  // hashcode based on the natural id
     }
 }
 ----
 
 That said, an implementation of `equals()` and `hashCode()` based on the generated identifier of the entity can work _if you're careful_.
+
+CAUTION: Your implementation of `equals()` must be written to accommodate the possibility that the object passed to the `equals()` might be a <<proxies-and-lazy-fetching,proxy>>.
+Therefore, you should use `instanceof`, not `getClass()` to check the type of the argument, and should access fields of the passed entity via its accessor methods.

hibernate-core/src/test/java/org/hibernate/orm/test/mapping/identifier/NaiveEqualsHashCodeEntityTest.java

@@ -185,11 +185,11 @@ public class NaiveEqualsHashCodeEntityTest extends BaseEntityManagerFunctionalTe
 			if (this == o) {
 				return true;
 			}
-			if (o == null || getClass() != o.getClass()) {
+			if (!(o instanceof Book)) {
 				return false;
 			}
 			Book book = (Book) o;
-			return Objects.equals(id, book.id);
+			return Objects.equals(id, book.getId());
 		}
 
 		@Override

hibernate-core/src/test/java/org/hibernate/orm/test/mapping/identifier/NaturalIdEqualsHashCodeEntityTest.java

@@ -164,11 +164,11 @@ public class NaturalIdEqualsHashCodeEntityTest extends BaseEntityManagerFunction
 			if (this == o) {
 				return true;
 			}
-			if (o == null || getClass() != o.getClass()) {
+			if (!(o instanceof Book)) {
 				return false;
 			}
 			Book book = (Book) o;
-			return Objects.equals(isbn, book.isbn);
+			return Objects.equals(isbn, book.getIsbn());
 		}
 
 		@Override