呈现页面之前的验证 [英] validation before rendering page

问题描述

我是JSF的新手，并使用JSF2来构建一个具有多个页面的webapp.我正在使用一个会话范围的Bean来保留通过浏览不同页面而设置的一些参数.

I'm new to JSF and using JSF2 to build a webapp which has several pages. I'm using a session scoped bean to keep some parameters that were set by going through the different pages.

当会话超时(或我重新部署应用程序)并且转到特定页面时，该页面将无法正确呈现，因为会话中缺少一些数据.此时，我希望显示主页.

When the session times out (or I redeploy the app) and I go to a specific page then this page is not able to render correctly because some data is missing from the session. At this point I want the home page to be shown.

我想对所有页面使用此机制.因此，总的来说，我想在呈现页面之前进行一些验证，如果验证失败，则将用户定向到主页.

I want to use this mechanism for all pages. So in general I want to do some validation before rendering a page and direct the user to the home page if the validation fails.

我应该如何处理?

推荐答案

在这种特殊情况下，我将使用简单的过滤器挂接到JSF请求并检查会话中托管bean的存在.下面的示例假定以下条件:

In this particular case I'd use a simple filter which hooks on JSF requests and checks the presence of the managed bean in the session. The below example assumes the following:

• FacesServlet在web.xml中定义为<servlet-name>facesServlet</servlet-name>
• 您的会话作用域bean的受管理bean名称为yourSessionBean.
• 您的主页位于home.xhtml

• FacesServlet is definied in web.xml as <servlet-name>facesServlet</servlet-name>
• Your session scoped bean has a managed bean name of yourSessionBean.
• Your home page is located at home.xhtml

@WebFilter(servletName="facesServlet")
public class FacesSessionFilter implements Filter {

    @Override
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;
        HttpSession session = request.getSession(false);

        if (!request.getRequestURI().endsWith("/home.xhtml") && (session == null || session.getAttribute("yourSessionBean") == null)) {
            response.sendRedirect(request.getContextPath() + "/home.xhtml"); // Redirect to home page.
        } else {
            chain.doFilter(req, res); // Bean is present in session, so just continue request.
        }
    }

    // Add/generate init() and destroy() with empty bodies.
}

或者，如果您想做更多JSF式的操作，请在主模板中添加<f:event type="preRenderView">.

Or if you want to do it more JSF-ish, add a <f:event type="preRenderView"> to the master template.

<f:metadata>
    <f:event type="preRenderView" listener="#{someBean.preRenderView}" />
</f:metadata>

使用

@ManagedProperty(value="#{yourSessionBean}")
private YourSessionBean yourSessionBean;

public void preRenderView() {
    if (yourSessionBean.isEmpty()) {
        yourSessionBean.addPage("home");
        FacesContext.getCurrentInstance().getExternalContext().redirect("/home.xhtml");
    }
}

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