jsp调用java类并查询sql数据库

jsp教程调用java类并查询sql数据库教程
package bean;
import java.sql.*;

public class MyDb_Page{
    private Statement stmt;
    private Connection conn=null;
    private ResultSet rs=null;
    private String navi;
   
    public void connection(String db_name,String user,String pwd) throws  Exception{
        Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
        String url="jdbc:mysql教程://www.111com.net:3306/" + db_name;
        conn=DriverManager.getConnection(url,user,pwd);
        stmt=conn.createStatement();
    }
   
    public ResultSet query(String sql) throws Exception{
        rs=stmt.executeQuery(sql);
        return rs;
    }

public ResultSet query(String query,int size,int page) throws Exception{
        int page_count;    //总页数
        int result_count;    //总记录数
        int begin;    //当前页第一条记录索引号
        String sql=query;
        int i=query.indexOf("from");
        String sql2=query.substring(i);
        rs=query("select count(*) " + sql2);
        rs.next();
        result_count=rs.getInt(1);
        page_count=(result_count + size - 1)/size;
        begin=(page-1)*size;
        String s=" limit " + begin + "," +size;
        sql=sql + s;
        rs=query(sql);
        //设置导航栏
        String back="没有了";
        String pre="没有了";
        if(page>1)    back="上一页";
        if(page下一页";
        navi=back + "      " + pre;
        return rs;
    }
   
    public String getNavi(){
        return navi;
    }

   
    public int update(String sql) throws  Exception{
        int n=0;
        n=stmt.executeUpdate(sql);
        return n;
    }
   
    public boolean delete(String sql) throws  Exception{
        boolean flag=false;
        flag=stmt.execute(sql);
        return flag;
    }
}
%>
<jsp:useBean id="www.111com.net" class="bean.MyDb_Page" scope="page"/>
<%
String sql="select * from student";
ResultSet rs=db.query(sql);
while(rs.next()){
   out.println(rs.getString(10);
}