mvc练手项目 三层结构 学生管理系统 jsp servlet

package service; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import Dao.indexDao; import db.db; public class indexImple implements indexDao { //查询数据库所有的值 @Override public List<Map<String, String>> selectall() { List<Map<String, String>> selectalllist = new ArrayList() ; String url = "jdbc:mysql://localhost:3306/sa"; db dbUtils = new db(url, "root", "root"); String sql = "select * from student"; //查询 返回的是一个数据结果集 使用 ResultSet rs ，然后遍历 ResultSet rs= dbUtils.executeQuery(sql); try { //这句是遍历结果集 while(rs.next()){ //获取每条数据里的字段对应的值 //rs.getString("id"); 括号里的内容是数据库的字段值 String id =rs.getString("id"); String name =rs.getString("name"); String age =rs.getString("age"); String sex =rs.getString("sex"); String Class =rs.getString("class"); String garden =rs.getString("garden"); //定义一个map，将循环的每条数据的每个值塞入到map里面 Map<String,String> map = new HashMap<String,String>(); map.put("id", id); map.put("name", name); map.put("age", age); map.put("sex", sex); map.put("Class", Class); map.put("garden", garden); //将每条数据对应的map 塞入到list selectalllist.add(map); } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } //返回list return selectalllist; } //查询student表的所有ID @Override public List<Map<String, String>> selectID() { List<Map<String, String>> idlist =new ArrayList() ; String url = "jdbc:mysql://localhost:3306/sa"; db dbUtils = new db(url, "root", "root"); String sql = "select * from student"; ResultSet rs= dbUtils.executeQuery(sql); try { while(rs.next()){ String id =rs.getString("id"); Map<String,String> map = new HashMap<String,String>(); map.put("id", id); idlist.add(map); } }catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } return idlist; } }