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note The full stack trace of the root cause is available in the Apache Tomcat

www.MyException.Cn  网友分享于:2013-09-12  浏览:4958次
servlet验证登录……
我写了个JSP用户通过SQL2005登录,但是发布后跳转出现了问题,以下是我代码:
  //获取用户名
String name=request.getParameter("admin");
//获取密码
String powd=request.getParameter("mm");
//属性、加载JDBC驱动、连接
Connection con=null;
Statement st=null;
ResultSet re=null;
try {
Class.forName("com.miscrosoft.sqlserver.jdbc.SQLServerDriver");
con=DriverManager.getConnection(
"jdbc:sqlserver://localhost:1433;databaseName=cd","asd","");
st=con.createStatement();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
//SQL语句
String sql="select * from admin where admin='"+name+"' and mm='"+powd+"'";

try {
re=st.executeQuery(sql);
} catch (SQLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}

try {
if(re.next()){// 有匹配的用户名和密码,登陆成功
  response.sendRedirect("htgl.jsp");
}
else{
response.sendRedirect("ht.jsp");
}
} catch (SQLException e) {
e.printStackTrace();
}
下面是出现的错误页面显示:
type Exception report

message 

description The server encountered an internal error () that prevented it from fulfilling this request.

exception 

java.lang.NullPointerException
com.servlet.ht_servlet.doPost(ht_servlet.java:52)
javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)


note The full stack trace of the root cause is available in the Apache Tomcat/6.0.13 logs.

这个是第52行re=st.executeQuery(sql);
谢谢大家了……


------解决方案--------------------
st应该是个null值
------解决方案--------------------
Java code

    String name = request.getParameter("username");
    String pwd = request.getParameter("password");
    //out.println(name+pwd);
    String sql ="select * from Info where username='"+name+"' and password='"+pwd+"'";
    //out.println(sql);
    Statement stm= null;
    ResultSet rs =null;
    try
    {
        stm = conn.createStatement();
        rs = stm.executeQuery(sql);
        if(rs.next())
        {
            session.setAttribute("username",name);
            response.sendRedirect("index.html");
        }
        else
        {
            response.sendRedirect("index1.html");
        }
    }
    catch(SQLException e)
    {
        e.printStackTrace();
    }
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