Overview of JSP/Servlet redirection technology

The redirection technology of JSP/Servlet is summarized as follows:
1. RequestDispatcher. forward ()
Is used on the server. When forward () is used, the Servlet engine transmits the HTTP request from the current Servlet or JSP to another Servlet, JSP or common HTML file, that is, your form is submitted to. jsp, in. jsp uses forward () to redirect to B. jsp. At this time, all information submitted by form is in B. jsp can be obtained, and parameters are automatically transmitted.
However, forward () cannot be redirected to a jsp file with a frame. It can be redirected to an html file with a frame. At the same time, forward () cannot be passed with parameters after it, such as servlet? Name = frank. If this is not the case, you can use response. setAttribute ("name", name) in the program to upload it to the next page.
The URL in the browser address bar remains unchanged after redirection.
For example, redirection in servlet
Public void doPost (HttpServletRequest request, HttpServletResponse response)
Throws ServletException, IOException
{
Response. setContentType ("text/html; charset = gb2312 ");
ServletContext SC = getServletContext ();
RequestDispatcher rd = null;
Rd = SC. getRequestDispatcher ("/index. jsp"); // Targeted page
Rd. forward (request, response );
}
Usually used in servlet, not in jsp.
2. response. sendRedirect ()
It works on the user's browser. sendRedirect () can be passed with parameters, such as servlet? Name = frank is uploaded to the next page, and can be redirected to different hosts. sendRedirect () can be used to redirect jsp files with frame.
After redirection, the URL of the redirection page will appear in the address bar of the browser.
For example, redirection in servlet
Public void doPost (HttpServletRequest request, HttpServletResponse response)
Throws ServletException, IOException
{
Response. setContentType ("text/html; charset = gb2312 ");
Response. sendRedirect ("/index. jsp ");
}
Because response is an implicit object in the jsp page, you can use response. sendRedirect () in the jsp page to directly implement relocation.
Note:
(1) when response. sendRedirect is used, no HTML output is available.
This is not absolute. The absence of HTML output means that HTML cannot be sent to a browser. In fact, the current server has a cache mechanism, generally at 8 K (I mean JSP SERVER), which means that unless you disable the cache or you use out. flush () force refresh. A small amount of HTML output is allowed before sendRedirect is used.