code: public final boolean abort()
      {
          boolean ret = false;
  
          if (UserLoginModule.LOG.isDebugEnabled()) {
              UserLoginModule.LOG.debug("Abort of " + this.principal);
          }
  
          // If our authentication was successful, just return false
          if (this.principal != null) {
  
              // Clean up if overall authentication failed
              if (this.committed) {
                  this.subject.getPrincipals().remove(this.principal);
              }
              this.committed = false;
              this.principal = null;
              ret = true;
          }
          return ret;
      }
docs: Abort the login.
  @return true if abort was successful