classdao.java

学生信息管理系统

package dao;
import java.sql.*;
import conn.ConnectDB;
import vo.*;
import java.util.*;
public class ClassDAO
{
	public ClassDAO()
	{
	}
	public String[]getClassNames()
	{
		ResultSet rs=null;
    	String[] className=null;
    	try
    	{
    		String sql="select className from class";
    		Connection conn = ConnectDB.getConnection();
			Statement stmt =conn.createStatement();
			rs=stmt.executeQuery(sql);
			int i=0;
    		while(rs.next())
    		{
    			i++;
    		}
    		
    		className = new String[i];
    		
    		rs.close();
    		rs=stmt.executeQuery(sql);
    		i=0;
    		while(rs.next())
    		{
    			className[i]=rs.getString(1).trim();;
    			i++;
    		}
    		conn.close();
    	}
    
	    catch(Exception e)
		{
			e.printStackTrace();
		}
		return 	className;
	}
	public ArrayList getClasses()
	{
		ArrayList classes=null;
		try
		{
			classes=new ArrayList();
			String sql="select * from class";
			Connection conn=ConnectDB.getConnection();
			Statement stat=conn.createStatement();
			ResultSet rs=stat.executeQuery(sql);
			while(rs.next())
			{
				ClassVO classvo=new ClassVO();
				classvo.setClassId(rs.getString("class_id").trim());
				classvo.setClassName(rs.getString("className").trim());
				classes.add(classvo);
			}
			conn.close();
		}
		 catch(Exception e)
		{
			e.printStackTrace();
		}
		return classes;
	}
	/*
	public static void main(String[] args)
	{
		ClassDAO classdao=new ClassDAO();
		String[] class_names=classdao.getClassNames();
		for(int i =0;i<class_names.length;i++)
		{
			System.out.println(class_names[i]);
		}
	}
	*/
}