servlet中处理用户非法登录页面
比如我们现在有两个页面，一个是登录页面（login.java），一个是登录后的欢迎页面（wel.java），现在我们只有先让用户正常登录后才能允许进入wel.jsp页面（也就是不准用户直接进入wel.jsp），这时我们就得用到session技术。
//login.java如下
package cn.hnu;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class testhtml extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
resp.setContentType("text/html;charset=gbk");
try {
PrintWriter pw = resp.getWriter();
pw.println("<html>");
pw.println("<head>");
pw.println("<title>");
pw.println("用户登录");
pw.println("</title>");
pw.println("</head>");
pw.println("<body>");
pw.println("<h1>用户登录</h1>");
pw.println("<hr>");
pw.println("<form method=post action=loginCl>");
pw.println("用户名：<input type=text name=userName><br>");
pw.println("密  码：<input type=password name=password><br>");
pw.println("<input type=submit value=登录>");
pw.println("<input type=reset value=重置>");
pw.println("</form>");
pw.println("</body>");
pw.println("</html>");
} catch (Exception e) {
e.printStackTrace();
// TODO: handle exception
}
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
// TODO Auto-generated method stub
this.doGet(req, resp);
}
}
//loginCl.java如下，它主要用于负责页面的转发及用户登录验证
package cn.hnu;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class loginCl extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
// TODO Auto-generated method stub
String u = req.getParameter("userName");
String p = req.getParameter("password");
if(u.equals("fxk")&& p.equals("123")){
HttpSession hs = req.getSession(true);
hs.setAttribute("pass", "OK");
resp.sendRedirect("wel");
}else{
resp.sendRedirect("login");
}
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
// TODO Auto-generated method stub
this.doGet(req, resp);
}
}
//wel.java如下，它主要用于用户正常登录后显示信息给用户
package cn.hnu;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class Wel extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
// TODO Auto-generated method stub
HttpSession hs = req.getSession();
String s = (String)hs.getAttribute("pass");
if(s == null){
resp.sendRedirect("login");
}
PrintWriter pw = resp.getWriter();
pw.write("welcome,hello");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
// TODO Auto-generated method stub
this.doGet(req, resp);
}
}