jsp数据库插不进数据

/**
HandleRegister.java
*
*
* @author
* @version 1.00 2012/6/16
*/

package myservlet.control;
import java.sql.*;
import mybean.data.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class HandleRegister extends HttpServlet {

public void init(ServletConfig config)throws ServletException
{super.init(config);
try{Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver");

}
catch(Exception e){

}
}
public String handleString(String s){
try{byte bb[]=s.getBytes("iso-8859-1");
s=new String(bb);
}
catch(Exception ee){}
return s;
}
public void doPost(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException
{Connection con;
String sql="";
Register reg=new Register();
request.setAttribute("register",reg);
String username=request.getParameter("username"),
password1=request.getParameter("password1"),
email=request.getParameter("email"),
sex=request.getParameter("sex");

String uri="jdbc:sqlserver://127.0.0.1:1433;DatabaseName=qinziyou";
boolean isLD=true;
for(int i=0;i<username.length();i++)
{char c=username.charAt(i);
if(!((c<='z'&&c>='a')||(c<='Z'&&c>='A')||(c<='9'&&c>='0')))
isLD=false;
}
String backNews="";


boolean success=true;
try{con=DriverManager.getConnection(uri,"sa","sa");
Statement statement=con.createStatement();
sql="SELECT * FROM Users WHERE username='"+username+"'";
ResultSet rs=statement.executeQuery(sql);
if(rs.next())
{backNews="该用户名已经存在，请更换用户名！";
reg.setBackNews(backNews);
success=false;

}
else {
sql="INSERT INTO Users(username,password,email,sex) VALUES('"+username+"','"+password1+"','"+email+"','"+sex+"')";
statement.executeUpdate(sql);
backNews="注册成功！";
reg.setBackNews(backNews);
reg.setUsername(username);
reg.setPassword(handleString(password1));
reg.setEmail(handleString(email));}

con.close();

}
catch(SQLException exp)
{backNews="HAHA该用户名已使用！";
reg.setBackNews(backNews);
success=false;

}

if(success)
{RequestDispatcher dispatcher=request.getRequestDispatcher("showRegisterMess2.jsp");
dispatcher.forward(request,response);}
else{ RequestDispatcher dispatcher=request.getRequestDispatcher("showRegisterMess1.jsp");
dispatcher.forward(request,response);}
}



public void doGet(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException
{doPost(request,response);
}
}



/**
Register.java
*
*
* @author
* @version 1.00 2012/6/16
*/
package mybean.data;

public class Register {

String username="",password="",email="";
String backNews;
public void setUsername(String name)
{username=name;
}
public String getUsername()
{return username;
}
public void setPassword(String pw )
{password=pw;
}
public String getPassword()
{return password;
}
public void setEmail(String em)
{email=em;
}
public String getEmail()
{return email;

}
public String getBackNews()
{return backNews;
}
public void setBackNews(String s)
{backNews=s;
}
}

我为什么总是插不进数据 呀 总是执行catch里面的语句呀