java web下开发二级级联下拉菜单（数据库实现的）

package com.niit.test; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ArrayList; import javax.sql.DataSource; import com.niit.model.BookType; public class GetDaoImpl implements IGetDao { private Connection conn =null; private PreparedStatement ps = null; private ResultSet rs = null; private DataSource ds = null; private int pageSize = 10; /** * 初始化数据源； */ public void initDataSource() { //初始化一个数据源 ds = ConnectionUtility.getDataSource(); try { //连接数据库 conn = ds.getConnection(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public ArrayList<BookType> getBKT(int bktid) { // TODO Auto-generated method stub initDataSource(); try { conn = ds.getConnection(); ps = conn.prepareStatement("SELECT * FROM BOOKTYPE WHERE BKTUPPERID=?"); ps.setInt(1, bktid); rs = ps.executeQuery(); ArrayList<BookType> list = new ArrayList<BookType>(); while(rs.next()) { BookType bktype = new BookType(); bktype.setBktid(rs.getInt(1)); bktype.setBktname(rs.getString(2)); bktype.setBktlevel(rs.getInt(3)); bktype.setUpperlevelid(rs.getInt(4)); list.add(bktype); } return list; } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { closeAll(); } return null; } public void closeAll() { try { if (rs != null) { rs.close(); } if (ps != null) { ps.close(); } if (conn != null) { conn.close(); } } catch(SQLException e) { e.printStackTrace(); } } }