How to inject Service and javafilter in Java Filter

How to inject Service and javafilter in Java Filter

A problem occurs in the project. If Serivce injection fails in the Filter, the injected service is always null. As follows:

public class WeiXinFilter implements Filter{        @Autowired    private UsersService usersService;

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest)request;
        HttpServletResponse resp = (HttpServletResponse)response;
　　　　 Users users = this.usersService.queryByOpenid(openid);

}

The above usersService will report a null pointer exception.

Solution:

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {        HttpServletRequest req = (HttpServletRequest)request;        HttpServletResponse resp = (HttpServletResponse)response;        ServletContext sc = req.getSession().getServletContext();
        XmlWebApplicationContext cxt = (XmlWebApplicationContext)WebApplicationContextUtils.getWebApplicationContext(sc);
        
        if(cxt != null && cxt.getBean("usersService") != null && usersService == null)
            usersService = (UsersService) cxt.getBean("usersService");
        
        Users users = this.usersService.queryByOpenid(openid);

That's all.

Method 2:

public class WeiXinFilter implements Filter{        private UsersService usersService;        public void init(FilterConfig fConfig) throws ServletException {        ServletContext sc = fConfig.getServletContext();         XmlWebApplicationContext cxt = (XmlWebApplicationContext)WebApplicationContextUtils.getWebApplicationContext(sc);                if(cxt != null && cxt.getBean("usersService") != null && usersService == null)            usersService = (UsersService) cxt.getBean("usersService");            }

Related Principles:

1. How to obtain ServletContext:

1) Get it directly in javax. servlet. Filter
ServletContext context = config. getServletContext ();

2) directly retrieve from HttpServlet
This. getServletContext ()

3) Use HttpServletRequest to obtain
Request. getSession (). getServletContext ();

2. WebApplicationContext and ServletContext(