java - 通过过滤器设置 FacesMessage

Question

在我的 JSF 应用程序中，有一个 Filter 用于检查身份验证过程。当认证失败时，过滤器重定向到login.xhtml。

如何将 FacesMessage 从 Filter 传递到我的登录页面？

虽然，我用了下面，还是不行。

FacesContext.getCurrentInstance().addMessage(null, new FacesMessage(FacesMessage.SEVERITY_ERROR, message, null));

AuthenticationFilter.java

public class AuthenticationFilter implements Filter  {
    private FilterConfig config;
    private ServletContext servletContext;

    public void init(FilterConfig filterConfig) {
        config = filterConfig;
        servletContext = config.getServletContext();
    }

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest httpRequest = (HttpServletRequest) servletRequest;
        HttpServletResponse httpResponse = (HttpServletResponse) servletResponse;
        HttpSession session = httpRequest.getSession();
        User user = (User) session.getAttribute(Constants.LOGIN_USER);
        if (user == null) {
            ...
            FacesContext.getCurrentInstance().addMessage(null, new FacesMessage(FacesMessage.SEVERITY_ERROR, message, null));

            String loginView = httpRequest.getContextPath() + Constants.LOGIN_PAGE;
            httpResponse.sendRedirect(loginView);
        } else if (!user.getRole().equals(Role.SYSTEM_ADMINISTRATOR)) {
            ....
            FacesContext.getCurrentInstance().addMessage(null, new FacesMessage(FacesMessage.SEVERITY_ERROR, message, null));

            String loginView = httpRequest.getContextPath() + Constants.LOGIN_PAGE;
            httpResponse.sendRedirect(loginView);
        } else {
            filterChain.doFilter(servletRequest, servletResponse);
        }
        servletContext.log("Exiting the filter");
    }

    public void destroy() {
        //Nothing to do.
    }
}

Answer 1

FacesContext由 FacesServlet 创建.当您在过滤器内时，它尚未被调用。过滤器在 servlet 之前运行。所以你永远无法得到 FacesContext在过滤器中。此外，面孔消息是请求范围内的，因此无论如何重定向都会使它们消失。

让login.xhtml在 <f:event type="preRenderView"> 期间自行设置.最简单的方法是让过滤器将其暂时放在 session 范围内。

session.setAttribute("message", message);
httpResponse.sendRedirect(loginView);

然后在 login.xhtml 的预渲染 View 监听器方法中将其从 session 范围中删除:

String message = (String) externalContext.getSessionMap().remove("message");

if (message != null) {
    context.addMessage(null, new FacesMessage(FacesMessage.SEVERITY_ERROR, message, null));
}