本文实例讲述了一个处理用户登陆的servlet实现方法。分享给大家供大家参考。具体分析如下：
Login.java代码如下：
复制代码代码如下:
package com.bai;
import javax.servlet.http.*;
import java.io.*;
public class Login extends HttpServlet{
public void doGet(HttpServletRequest req,HttpServletResponse res){
try{req.setCharacterEncoding("gb2312");
res.setContentType("text/html;charset=gb2312");
PrintWriter pw=res.getWriter();
pw.println("<html>");
pw.println("<body>");
pw.println("<h1>登陆界面</h1>");
pw.println("<form action=logincl method=post>");
pw.println("用户名:<input type=text name=username><br>");
pw.println("密码:<input type=password name=passwd><br>");
pw.println("<input type=submit value=login><br>");
pw.println("</form>");
pw.println("</body>");
pw.println("</html>");
}
catch(Exception e){
e.printStackTrace();
}
}
public void doPost(HttpServletRequest req,HttpServletResponse res){
this.doGet(req,res);
}
}
LoginCl.java代码如下：
复制代码代码如下:
package com.bai;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;
public class LoginCl extends HttpServlet{
public void doGet(HttpServletRequest req,HttpServletResponse res){
Connection conn=null;
Statement stmt=null;
ResultSet rs=null;
String sql = "select username,passwd from users where username = ? and passwd = ?";
try{//req.setCharacterEncoding("gb2312");
String user=req.getParameter("username");
String password=req.getParameter("passwd");
Class.forName("com.mysql.jdbc.Driver");
conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/sqdb","root","root");
// stmt=conn.createStatement();
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setString(1, user);
pstmt.setString(2, password);
rs = pstmt.executeQuery();
// rs=stmt.executeQuery("select top 1 * from users where username='"+user
// +"' and passwd='"+password+"'");
if(rs.next())
{
HttpSession hs=req.getSession(true);
hs.setMaxInactiveInterval(60);
hs.setAttribute("name",user);
res.sendRedirect("welcome?&uname="+user+"&upass="+password);
}
else{
res.sendRedirect("login"); //url
}
}
catch(Exception e){
e.printStackTrace();
}finally{
try{
if(rs!=null){
rs.close();
}
if(stmt!=null){
stmt.close();
}
if(conn!=null){
conn.close();
}
}catch(Exception e){
e.printStackTrace();
}
}
}
public void doPost(HttpServletRequest req,HttpServletResponse res){
this.doGet(req,res);
}
}
其实上面这个处理用户名密码带有明显注入漏洞，可以根据用户名从数据库取密码，用取出的密码和用户输入的密码比较
复制代码代码如下:
sql=select passwd from users where username = ? limit 1
if(rs.next())
{
String passwd=rs.getString(1);
if(passwd.equals(password))
//密码正确
else //密码错误
}
Welcome.java代码如下：
复制代码代码如下:
package com.bai;
import javax.servlet.http.*;
import java.io.*;
public class Welcome extends HttpServlet{
public void doGet(HttpServletRequest req,HttpServletResponse res){
HttpSession hs=req.getSession();
String val=(String)hs.getAttribute("pass");
if(val==null){
try{
System.out.print(1);
res.sendRedirect("login");
}catch(Exception e){
e.printStackTrace();
}
}
String u=req.getParameter("uname");
String p=req.getParameter("upass");
try{//req.setCharacterEncoding("gb2312");
PrintWriter pw=res.getWriter();
pw.println("welcome! "+u+"&pass="+p);
}
catch(Exception e){
e.printStackTrace();
}
}
public void doPost(HttpServletRequest req,HttpServletResponse res){
this.doGet(req,res);
}
}
希望本文所述对大家的Java程序设计有所帮助。