You can implement a simple solution with spring security. The idea is to create a class that implements org.springframework.security.access.PermissionEvaluator and override the method hasPermission. Look the next example:
@Component("permissionEvaluator")
public class PermissionEvaluator implements org.springframework.security.access.PermissionEvaluator {
/**
* @param authentication represents the user in question. Should not be null.
* @param targetDomainObject the domain object for which permissions should be
* checked. May be null in which case implementations should return false, as the null
* condition can be checked explicitly in the expression.
* @param permission a representation of the permission object as supplied by the
* expression system. Not null.
* @return true if the permission is granted, false otherwise
*/
@Override
public boolean hasPermission(Authentication authentication, Object targetDomainObject, Object permission) {
if (authentication != null && permission instanceof String) {
User loggedUser = (User) authentication.getPrincipal();
String permissionToCheck = (String) permission;
// in this part of the code you need to check if the loggedUser has the "permission" over the
// targetDomainObject. In this implementation the "permission" is a string, for example "read", or "update"
// The targetDomainObject is an actual object, for example a object of UserProfile class (a class that
// has the profile information for a User)
// You can implement the permission to check over the targetDomainObject in the way that suits you best
// A naive approach:
if (targetDomainObject.getClass().getSimpleName().compareTo("UserProfile") == 0) {
if ((UserProfile) targetDomainObject.getId() == loggedUser.getId())
return true;
}
// A more robust approach: you can have a table in your database holding permissions to each user over
// certain targetDomainObjects
List<Permission> userPermissions = permissionRepository.findByUserAndObject(loggedUser,
targetDomainObject.getClass().getSimpleName());
// now check if in userPermissions list we have the "permission" permission.
// ETC...
}
//access denied
return false;
}
}
Now, with this implementation you can use in for example your service layer the @PreAuthorize annotation like this:
@PreAuthorize("hasPermission(#profile, 'update')")
public void updateUserProfileInASecureWay(UserProfile profile) {
//code to update user profile
}
The "hasPermission" inside the @PreAuthorize annotation receives the targetDomainObject #profile from the params of the updateUserProfileInASecureWay method and also we pass the required permission (in this case 'update').
This solution avoids all the complexity of the ACL by implementing a "small" ACL. Maybe it can work for you.
