编码方式我都改成了gbk，为什么mysql里中文还是乱码

package A;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;



public class add extends HttpServlet {

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


PrintWriter out = response.getWriter();
Connection conn=null;
PreparedStatement st=null;
try {
Class.forName("com.mysql.jdbc.Driver");
String url="jdbc:mysql://localhost:3306/qiche";
String user="root";
String password="123456";

conn=DriverManager.getConnection(url, user, password);
st=conn.prepareStatement("select * from info where leixing=?");

st.setString(1, request.getParameter("leixing"));
ResultSet rs=st.executeQuery();
if (rs.next()){
request.getRequestDispatcher("add.jsp").forward(request, response);
}
else
{
request.setCharacterEncoding("gbk");


st=conn.prepareStatement("insert into info values(?,?,?)");
request.setCharacterEncoding("gbk");
st.setString(1,request.getParameter("leixing"));
st.setString(2,request.getParameter("chepai"));
st.setString(3,request.getParameter("or"));
int m=st.executeUpdate();
if(m!=0){
request.getRequestDispatcher("tianjia.jsp").forward(request, response);
}
else{
request.getRequestDispatcher("add.jsp").forward(request, response);
}
}
}catch (Exception e){

System.out.println(e.getMessage());
e.printStackTrace();
}
}

private void mysql_query(String string) {
// TODO Auto-generated method stub

}

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