spring - Spring Security:访问servlet Filter中当前经过身份验证的User

我最近开始学习Spring安全性，今天我提出了一个基本的（我相信）问题：为什么我不能访问servlet过滤器中的当前主体，如下所示：

package com.acme.test;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

import org.springframework.security.core.Authentication;
import org.springframework.security.core.context.SecurityContext;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.stereotype.Component;

@Component
public class TestFilter implements Filter {

    /*
     * (non-Javadoc)
     *
     * @see javax.servlet.Filter#init(javax.servlet.FilterConfig)
     */
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        // TODO Auto-generated method stub

    }

    /*
     * (non-Javadoc)
     *
     * @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest,
     * javax.servlet.ServletResponse, javax.servlet.FilterChain)
     */
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {

        SecurityContext securityContext = SecurityContextHolder.getContext();
        Authentication auth = securityContext.getAuthentication();

        // auth is null here

        chain.doFilter(request, response);
    }

    /*
     * (non-Javadoc)
     *
     * @see javax.servlet.Filter#destroy()
     */
    @Override
    public void destroy() {
        // TODO Auto-generated method stub

    }

}

使用authentication auth=securityContext.getauthentication（）；检索的身份验证对象为空。当在MVC@Controller中使用上述代码片段时，它工作得很好（如预期的那样）。
为什么会这样？

最佳答案

内部：

HttpServletRequest request = (HttpServletRequest) request;
HttpSession session = request.getSession(false);

SecurityContextImpl sci = (SecurityContextImpl) session.getAttribute("SPRING_SECURITY_CONTEXT");

if (sci != null) {
        UserDetails cud = (UserDetails) sci.getAuthentication().getPrincipal();
        // do whatever you need here with the UserDetails
}

希望这有帮助