JSP 转发与重定向和浏览器 URL
我对 JSP/Servlet 设置以及浏览器 URL 中显示的内容有疑问。 page1.jsp 通过带有“SAVE.do”操作的表单提交到 servlet。 Servlet 希望在保存时将成功消息传递回 page1.jsp。 将消息放入请求中来做到这一点
request.setAttribute("message", "Save Successful");
我通过使用I then call
request.getRequestDispatcher("page1.jsp").forward(req,resp);
，但是，浏览器将显示 http:// /localhost:8080/SAVE.do 而不是 http://localhost:8080/page1.jsp
当我更改转发时使用重定向
response.sendRedirect("page1.jsp");
然后该属性就会丢失。
我想我正在寻找正确的方法来执行此操作，以便在再次加载 page1.jsp 时可以取回该属性，并在浏览器中显示正确的 URL。
I have an issue with a JSP/Servlet set-up and what's getting displayed in the browser URL. page1.jsp submits to the servlet by a form with an action of "SAVE.do". The servlet wants to pass a success message back to page1.jsp on the save. I do this by placing the message in the request using the
request.setAttribute("message", "Save Successful");
I then call
request.getRequestDispatcher("page1.jsp").forward(req,resp);
However, the browser will display the URL of http://localhost:8080/SAVE.do instead of http://localhost:8080/page1.jsp
When I change the forward to a redirect using
response.sendRedirect("page1.jsp");
Then the attribute is lost.
I guess I'm looking for the right way to do this, so that I can get the attribute back when page1.jsp loads again, WITH the right URL displaying in the browser.
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正确的 URL 是浏览器提交的 URL。请求首先由 servlet 处理，然后由 JSP 处理，这一事实与浏览器无关。顺便说一句，JSP 很可能位于受保护的文件夹中（如
/WEB-INF），因为浏览器从不直接向此 JSP 发送请求，而是通过调度程序 servlet 的 URL 发送请求。重定向与转发完全不同。转发意味着：我使用另一个服务器组件来完成我的请求的处理。重定向的意思是：我已经处理完请求，我会要求浏览器去访问另一个URL，从而发出一个新的请求。这个新 URL 可以是完全外部的 URL（例如 google.com）。
在您的情况下，您可能需要应用 post-redirect-get 模式，这样“成功”页面的刷新就不会触发表单的重新提交。但是，如果您想显示动态选择的消息，则必须将其保存到会话中并在第二个请求中检索它。不过，如果您想正确应用 MVC 模式，您的第二个请求也应该通过 servlet。
请注意，大多数 MVC 框架都支持 post-redirect-get 模式。
The right URL is the one the browser submitted to. The fact that the request is first handled by a servlet and then by a JSP is irrelevant to the browser. BTW, the JSP could very well be in a protected folder (like
/WEB-INF), since the browser never sends a request to this JSP directly, but does through the URL of the dispatcher servlet.A redirect is a totally different thing than a forward. Forward means : I use another server component to finish the handling of my request. Redirect means : I have finished handling the request, and I'll ask the browser to go visit another URL, and thus make a new request. This new URL could be a totally external URL (google.com for example).
In your situation, you might want to apply the post-redirect-get pattern, so that a refresh of the "success" page doesn't trigger the re-submission of the form. But if you want to display a dynamically chosen message, you'll have to save it into the session and retrieve it in the second request. Your second request should go through a servlet as well, though, if you want to apply the MVC pattern correctly.
Note that most MVC frameworks have suppport for the post-redirect-get pattern.