package guestbook;import javax.servlet.*;import javax.servlet.http.*;import java.io.*;import sun.misc.BASE64Decoder;public class adminlogin extends HttpServlet{  public void doGet(HttpServletRequest request,    HttpServletResponse response) throws ServletException,    IOException  {    Init init=new Init(getServletContext().getRealPath("/"));    response.setContentType("text/html; charset=GB2312");    //get authorization header    String authorization = request.getHeader("Authorization");    if (authorization == null)    {      challenge(response); //no authorization so challenge    }    else    {      //determine if client is using basic authentication      if (!authorization.toLowerCase().startsWith("basic"))      {        challenge(response); //not basic so challenge      }      //取經過base64編碼后的帳號和密碼，從字符串第六位開始取      String namePass = authorization.substring(6).trim();      //instantiate Base64 decoder      BASE64Decoder decode = new BASE64Decoder();      //decode username and password      namePass = new String(decode.decodeBuffer(namePass));      int colon = namePass.indexOf(":");      //get username and password from decoded authorization text      String username = namePass.substring(0, colon);      String password = namePass.substring(colon+1);      //validate username and password (case sensitive)      if (!username.equals(init.getSuperName()) ||!password.equals(init.getSuperPassword()))      {        challenge(response); //invalid credentials so challenge      }      else      {        //驗證通過后就寫如cookie        Cookie myCookie=new Cookie("ADMIN",init.getSuperName());        response.addCookie(myCookie);        response.sendRedirect("index.jsp");      }    }  }//向瀏覽器響應401頭  private void challenge(HttpServletResponse response)  {    response.setStatus(response.SC_UNAUTHORIZED);    response.setHeader("WWW-Authenticate", "Basic realm=\"Login\"");  }}