ajax+servlet+jsp登录web小程序

package utils; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ArrayList; import java.util.List; import utils.DBUtils; import beans.UserBean; public class DBConn { Connection conn = null; PreparedStatement pstmt = null; ResultSet result = null; List<UserBean> userlist = null; UserBean user = null; //1.增加信息 public void add(UserBean user) { String sql = "insert into db_user values(?,?)"; try { conn = DBUtils.getConnection(); pstmt = conn.prepareStatement(sql); pstmt.setString(1, user.username); pstmt.setString(2, user.password); pstmt.executeUpdate(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ try { pstmt.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } //2.删除信息 public void delete(UserBean user) { String sql = "delete from db_user where username = ?"; try { conn = DBUtils.getConnection(); pstmt = conn.prepareStatement(sql); pstmt.setString(1, user.username); pstmt.executeUpdate(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ try { pstmt.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } //3.更新信息 public void update(UserBean user) { String sql = "update db_user set password=? where username = ?"; try { conn = DBUtils.getConnection(); pstmt = conn.prepareStatement(sql); pstmt.setString(1,user.password); pstmt.setString(2,user.username); pstmt.executeUpdate(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ try { pstmt.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } //4.查找信息 public List<UserBean> select() { try { //user = new UserBean(); userlist = new ArrayList<UserBean>(); conn = DBUtils.getConnection(); String sql = "select * from db_user"; pstmt = conn.prepareStatement(sql); result = pstmt.executeQuery(); while(result.next()){ user = new UserBean(); user.username = result.getString("username"); user.password = result.getString("password"); userlist.add(user); } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } finally{ try { pstmt.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } return userlist; } }