Grails如何在没有对象注入的情况下注入正在扩展savedRequestAwareAuthenticationSuccessHandler的类的bean

Question

SuccessHandler：

import React from 'react'
import ReactDOM from 'react-dom'
import {ButtonToolbar, Button} from 'react-bootstrap' // define individual controls to import    
const buttonsInstance = (
  <ButtonToolbar>
    <Button bsStyle="primary" bsSize="large" active>Primary button</Button>
    <Button bsSize="large" active>Button</Button>
  </ButtonToolbar>
);

ReactDOM.render(buttonsInstance, document.getElementById('root'));

资源：

class SuccessHandler extends SavedRequestAwareAuthenticationSuccessHandler{
    public void onAuthenticationSuccess(final HttpServletRequest request, final HttpServletResponse response,
                                        final Authentication authentication) throws ServletException, IOException {
        String targetUrl = determineTargetUrl(request, response)
        redirectStrategy.sendRedirect(request, response, targetUrl)
    }
    @Override
    protected String determineTargetUrl(HttpServletRequest request,
                                        HttpServletResponse response) {
        boolean hasAdmin =SpringSecurityUtils.ifAllGranted("ROLE_ADMIN");
        boolean hasUser=SpringSecurityUtils.ifAllGranted("ROLE_USER");

        if(hasAdmin){
            return adminUrl;
        }else if (hasUser){
            return userUrl
        }else{
            return super.determineTargetUrl(request, response);
        }
    }
    private String adminUrl
    private String userUrl

    public void setAdminUrl(String adminUrl){
        this.adminUrl = adminUrl
    }

    public void setUserUrl(String userUrl){
        this.userUrl = userUrl
    }

}

我想知道虽然没有创建任何对象，但import successHandler.SuccessHandler // Place your Spring DSL code here beans = { authenticationSuccessHandler(SuccessHandler) { adminUrl = '/admin/adminPanel' userUrl = '/' } } 和adminUrl属性是如何被注入的？

据我所知，我们应该创建一个对象，例如userUrl。这会使用Autowired创建对象，然后该对象将被注入资源bean中定义的属性。

但是，这里如何在没有创建任何对象的情况下注入属性？