According to the documentation on Symfony.com(1), the class named Group should implements RoleInterface.

http-teapot · http-teapot · commit 09d4488772e8 · 2012-05-17T11:40:22.000-07:00
However, when implementing ACLs, the code I modified would look for the Role class and therefore saves the Group as an object rather than saving the role name of the group. (1)http://symfony.com/doc/current/cookbook/security/entity_provider.html#managing-roles-in-the-database
diff --git a/src/Symfony/Component/Security/Acl/Domain/RoleSecurityIdentity.php b/src/Symfony/Component/Security/Acl/Domain/RoleSecurityIdentity.php
@@ -30,7 +30,7 @@ final class RoleSecurityIdentity implements SecurityIdentityInterface
      */
     public function __construct($role)
     {
-        if ($role instanceof Role) {
+        if ($role instanceof RoleInterface) {
             $role = $role->getRole();
         }
 

Original file line number	Diff line number	Diff line change
`@@ -30,7 +30,7 @@ final class RoleSecurityIdentity implements SecurityIdentityInterface`
`30`	`30`	`*/`
`31`	`31`	`public function __construct($role)`
`32`	`32`	`{`
`33`		`- if ($role instanceof Role) {`
	`33`	`+ if ($role instanceof RoleInterface) {`
`34`	`34`	`$role = $role->getRole();`
`35`	`35`	`}`
`36`	`36`