[英]What is the difference between redirect and navigation/forward and when to use what?

What is difference between a navigation in JSF


FacesContext context = FacesContext.getCurrentInstance();
context.getApplication().getNavigationHandler().handleNavigation(context, null, url);

and a redirect


HttpServletResponse response = (HttpServletResponse) FacesContext.getCurrentInstance().getExternalContext().getResponse();

and how to decide when to use what?


The issue with navigation is that page URL does not change unless faces-redirect=true is added to the query string of the navigation URL. However, in my case appending faces-redirect=true throws error if I want to redirect to a non-JSF page like a plain HTML page.

导航的问题是,除非将faces-redirect=true添加到导航URL的查询字符串中,否则页面URL不会更改。但是,在我的情况下,如果我想重定向到一个非jsf页面,比如一个普通的HTML页面,那么append -redirect=true抛出错误。

And another option is as BalusC suggested at JSF 2.0 redirect error

另一个选项是BalusC在JSF 2.0重定向错误中建议的。

1 个解决方案



First of all, the term "redirect" is in web development world the action of sending the client an empty HTTP response with just a Location header with therein the new URL on which the client has to send a brand new GET request. So basically:


  • Client sends a HTTP request to somepage.xhtml.
  • 客户机向somepage.xhtml发送一个HTTP请求。
  • Server sends a HTTP response back with Location: newpage.xhtml header
  • 服务器发送一个带有位置的HTTP响应:newpage。xhtml页眉
  • Client sends a HTTP request to newpage.xhtml (this get reflected in browser address bar!)
  • 客户端发送一个HTTP请求到newpage。xhtml(这在浏览器地址栏中得到了体现!)
  • Server sends a HTTP response back with content of newpage.xhtml.
  • 服务器以newpage.xhtml的内容发送HTTP响应。

You can track it with the webbrowser's builtin/addon developer toolset. Press F12 in Chrome/IE9/Firebug and check the "Network" section to see it.

您可以使用webbrowser的builtin/addon developer工具集跟踪它。按F12在Chrome/IE9/Firebug,并检查“网络”部分看它。

The JSF navigationhandler doesn't send a redirect. Instead, it uses the content of the target page as HTTP response.

JSF navigationhandler不发送重定向。相反,它使用目标页面的内容作为HTTP响应。

  • Client sends a HTTP request to somepage.xhtml.
  • 客户机向somepage.xhtml发送一个HTTP请求。
  • Server sends a HTTP response back with content of newpage.xhtml.
  • 服务器以newpage.xhtml的内容发送HTTP响应。

However as the original HTTP request was to somepage.xhtml, the URL in browser address bar remains unchanged. If you are familiar with the basic Servlet API, then you should understand that this has the same effect as RequestDispatcher#forward().

但是,由于最初的HTTP请求是在somepage上的。xhtml中,浏览器地址栏中的URL保持不变。如果您熟悉基本的Servlet API,那么您应该理解这与RequestDispatcher#forward()具有相同的效果。

As to whether pulling the HttpServletResponse from under the JSF hoods and calling sendRedirect() on it is the proper usage; no, that isn't the proper usage. Your server logs will get cluttered with IllegalStateExceptions because this way you aren't telling JSF that you've already taken over the control of the response handling and thus JSF shouldn't do its default response handling job. You should in fact be executing FacesContext#responseComplete() afterwards.


Also, everytime whenever you need to import something from javax.servlet.* package in a JSF artifact like a managed bean, you should absolutely stop writing code and think twice if you're really doing things the right way and ask yourself if there isn't already a "standard JSF way" for whatever you're trying to achieve and/or if the task really belongs in a JSF managed bean (there are namely some cases wherein a simple servlet filter would have been a better place).


The proper way of performing a redirect in JSF is using faces-redirect=true query string in the action outcome:


public String submit() {
    // ...
    return "/newpage.xhtml?faces-redirect=true";

Or using ExternalContext#redirect() when you're not inside an action method such as an ajax or prerender listener method:


public void listener() throws IOException {
    // ...
    ExternalContext ec = FacesContext.getCurrentInstance().getExternalContext();
    ec.redirect(ec.getRequestContextPath() + "/newpage.xhtml");

(yes, you do not need to put a try-catch around it on IOException, just let the exception go through throws, the servletcontainer will handle it)


Or using NavigationHandler#handleNavigation() in specific cases if you're using XML navigation cases and/or a custom navigation handler with some builtin listener:


public void listener() {
    // ...
    FacesContext fc = FacesContext.getCurrentInstance();
    NavigationHandler nh = fc.getApplication().getNavigationHandler();
    nh.handleNavigation(fc, null, "/newpage.xhtml?faces-redirect=true");

As to why the navigation handler fails for "plain HTML" files, that is simply because the navigation handler can process JSF views only, not other files. You should be using ExternalContext#redirect() then.


See also:



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