Servlet Filter filter Determines whether a user logs on (JSP page) __js

filter servlet class:

Package servlet;
Import java.io.IOException;

Import Java.io.PrintWriter;
Import Javax.servlet.Filter;
Import Javax.servlet.FilterChain;
Import Javax.servlet.FilterConfig;
Import Javax.servlet.RequestDispatcher;
Import javax.servlet.ServletException;
Import Javax.servlet.ServletRequest;
Import Javax.servlet.ServletResponse;
Import Javax.servlet.http.HttpServlet;
Import Javax.servlet.http.HttpServletRequest;
Import Javax.servlet.http.HttpServletResponse;


	Import javax.servlet.http.HttpSession;

		 public class Loginfilter implements Filter {private static final String Logon_uri = "Logon_uri";

		 private static final String Register_uri = "Register_uri";

		 Private String logon_page;

		 Private String register_page; public void Destroy () {} public void Dofilter (ServletRequest request, servletresponse response, Filterchain C
		  Hain) throws IOException, servletexception {httpservletrequest req = (httpservletrequest) request; HttpServletResponse resp = (HttPservletresponse) response;
		  Resp.setcontenttype ("text/html;");
		  Resp.setcharacterencoding ("Utf-8");
		 HttpSession session = Req.getsession ();
		  PrintWriter out = Resp.getwriter ();
		  Gets the URI String Request_uri = Req.getrequesturi () of the user request;
		  Gets the context path of the Web application String Ctxpath = Req.getcontextpath ();
		  Remove the context path and get the remaining part of the path String uri = request_uri.substring (Ctxpath.length ());
		   Determine if the user is accessing the login page if (uri.equals (logon_page) | | uri.equals (register_page)) {Chain.dofilter (request, response);
		  Return else {//If the access is not a login page, determine if the user has logged on if (null!= session.getattribute ("Curuser") && "!= session.
		    GetAttribute ("Curuser")) {Chain.dofilter (request, response);
		   Return else {String msg = "You are not logged in."
	           ";
	             String url = "Errorer";
	             Req.setattribute ("Err", msg);
	  		     RequestDispatcher dis = req.getrequestdispatcher (URL);
		   Dis.forward (req, resp);
		  }  Out.println ("<script language=/" javascript/">"//+ "parent.location.href=" "+//ctxpath + logon_page
		   + "'"//+ "</script>");
		  Return 
		  }} public void init (Filterconfig config) throws servletexception {//TODO auto-generated a stub
		  Get the login page and the URI logon_page = Config.getinitparameter (Logon_uri) from the deployment descriptor;
		  Register_page = Config.getinitparameter (Register_uri);
		  System.out.println (Logon_page);
		  if (null = = Logon_page | | | null = register_page) {throw new Servletexception ("No login page or homepage found"); }
		 }

	}

To modify the Web core configuration file:

Note: The tomcat server needs to be restarted after saving

<filter>
    <filter-name>loginFilter</filter-name>
    <filter-class>servlet. loginfilter</filter-class>
    <init-param>
          <param-name>LOGON_URI</param-name>
          <param-value>/login.jsp</param-value>
    </init-param>
    <init-param>
          < param-name>register_uri</param-name>
          <param-value>/register.jsp</param-value>
    </init-param>
  </filter>
<filter-mapping>
	<filter-name> charseterencodingfilter</filter-name>
	<url-pattern>/*</url-pattern>
</ filter-mapping>
 <filter-mapping>
   <filter-name>loginFilter</filter-name>
   <url-pattern>*.jsp</url-pattern>
  </filter-mapping>

Errorer Error Information Processing class:

Package servlet;
Import java.io.IOException;

Import Java.io.PrintWriter;
Import Javax.servlet.RequestDispatcher;
Import javax.servlet.ServletException;
Import Javax.servlet.http.HttpServlet;
Import Javax.servlet.http.HttpServletRequest;

Import Javax.servlet.http.HttpServletResponse; /** * Servlet Implementation Class ERROR */public class Errorer extends HttpServlet {private static final long seria

	Lversionuid = 1L; protected void ProcessRequest (HttpServletRequest request, httpservletresponse response) throws Servletexception, IO
			        Exception {response.setcontenttype ("text/html;charset=utf-8");
			        PrintWriter out = Response.getwriter ();
			        String url= "login.jsp";
			            try {out.println (" 
Effect Display: