从子类中的重写方法访问超类方法中的局部变量

Question

Is there a way in Java, either via reflection or other means, to access a local variable declared in a superclass' method from its corresponding overridden method in the subclass?

Specifically, I am working with Spring Security's DefaultLdapAuthoritiesPopulator . This class has a method named getAdditionalRoles which the documentation says subclasses can override to return extra roles for the user.

The class also implements the getGrantedAuthorities method, which actually calls the getAdditionalRoles method. The source code looks something like this:

public final GrantedAuthority[] getGrantedAuthorities(DirContextOperations user, String username) {
    ...
    Set roles = getGroupMembershipRoles(userDn, username);

    Set extraRoles = getAdditionalRoles(user, username);

    ...
}

This method calls getGroupMembershipRoles , which does an LDAP search for groups defined for this user and stores it in a local variable named roles . Now in my implementation of getAdditionalRoles , I also need access to the groups defined for this user in LDAP, so I can infer additional roles for this user. For business reasons, I cannot define these additional roles directly in LDAP.

I could simply go ahead and implement LdapAuthoritiesPopulator myself, but I was wondering if there was some other way around, as all I really need is access to the roles local variable in the parent class' method to avoid me having to do a second LDAP search.

Answer 1

1. you cann't access variables in other method, for variables in method is removed after the method is returned. because variables is in stack.
2. if possible, you can override getGroupMembershipRoles and get groups stored as property, and access it at other method.

Answer 2

Possibly you could leverage AOP and put After Retuning Advice on getGroupMembershipRoles(userDn, username); and modify the returned Roles.

Answer 3

I took Zutty's advice and implemented it this way:

@Override
public Set<GrantedAuthority> getGroupMembershipRoles(String userDn,
        String username) {
    Set<GrantedAuthority> authorities = super.getGroupMembershipRoles(userDn, username);

    // My app's logic by inspecting the authorities Set

    return authorities;

}

Answer 4

I dont think you can access data from local variables from any method(who's value method does not return) which is present in some other remote class. Even reflections wont help in this case. Please correct me if I am wrong or missed anything.