Using filter filter to implement login authorization

1. First write a permission filtering filter class to implement the filter interface
Import Javax.servlet.Filter;
Import Javax.servlet.FilterConfig;
Import javax.servlet.ServletException;
Import Javax.servlet.ServletRequest;
Import Javax.servlet.ServletResponse;
Import Javax.servlet.FilterChain;
Import java.io.IOException;
Import Javax.servlet.http.HttpServletRequest;
Import javax.servlet.http.HttpSession;
Import Javax.servlet.http.HttpServletResponse;

public class Rightfilter
Implements Filter ... {
public void init (Filterconfig filterconfig) throws Servletexception ... {
}

public void Dofilter (ServletRequest request, servletresponse response,
Filterchain chain) throws IOException, servletexception ... {
HttpServletRequest req = (httpservletrequest) request;
HttpServletResponse res = (httpservletresponse) response;

HttpSession session = Req.getsession (true);

User name information taken from the session
String username = (string) session.getattribute ("username");

If you don't get the user information, jump to the landing page
if (username = null | | "". Equals (username)) ... {
Jump to landing page
Res.sendredirect ("http://" +req.getheader ("Host") + "/login.jsp");
}
else ... {
Have logged in, continue this request
Chain.dofilter (Request,response);
}
}

public void Destroy () ... {
}
}

2. Then configure the JSP files that require login authorization in Web.xml:

     A. If a specific JSP file (such as a.jsp) requires login validation < Web-app >
   ....
   < filter >
     < filter-name > right </filter-name >
&nbs p;    < Filter-class > com.taihuatalk.taihua.common.RightFilter </filter-class >
   </filter >

   < filter-mapping >
     < Filter-name > Right </filter-name >
     < url-pattern >/a.jsp </url-pattern >
   </filter-mapping >
   ....
</Web-app >

    B. If it is a directory (such as A/directory) the entire directory of files need to login verification: < Web-app >
  
   < filter >
     < filter-name > right </filter-name >
&nbs p;    < Filter-class > com.taihuatalk.taihua.common.RightFilter </filter-class >
   </filter >

   < filter-mapping >
     < Filter-name > Right </filter-name >
     < url-pattern >/a/* </url-pattern &G T
   </filter-mapping >
   ....
</web-app >