JAVA之连接MySQL数据库——源码下载

package com.cy.dao; import java.sql.Connection; import java.sql.SQLException; import java.sql.Statement; import java.util.Map; import com.cy.po.User; import com.cy.util.DBConnection; public class UserDao { public UserDao(){} private static UserDao userDao = new UserDao(); public static UserDao getInstance(){ return userDao; } /** * 添加数据 * @param user * @return */ public boolean saveUser(User user){ boolean flag = false; String sql = "insert into user(username,password) values('"+user.getUsername()+"','"+user.getPassword()+"')"; flag = DBConnection.update(sql); return flag; } /** * 删除数据 * @param userId * @return */ public boolean deleteUserByUserId(int userId){ boolean flag = false; Connection conn = null; Statement st = null; try { conn = DBConnection.getConnection(); String sql = "delete from user where userId="+userId; st = conn.createStatement(); int row = st.executeUpdate(sql); if(row>0){ flag = true; } } catch (SQLException e) { e.printStackTrace(); }finally{ DBConnection.closeAll(st, conn); } return flag; } /** * 修改数据，参数是Map * @param map * @return */ public boolean updateUserByMap(Map<String, Object> map){ boolean flag = false; Connection conn = null; Statement st = null; try { conn = DBConnection.getConnection(); String sql = "update user set password='"+(String)map.get("password")+"' where userId="+(Integer)map.get("id"); st = conn.createStatement(); int row = st.executeUpdate(sql); if(row>0){ flag = true; } } catch (SQLException e) { e.printStackTrace(); }finally{ DBConnection.closeAll(st, conn); } return flag; } /** * 修改数据 * @param id * @param pass * @return */ public boolean updateUserByUserId(int id,String pass){ boolean flag = false; Connection conn = null; Statement st = null; try { conn = DBConnection.getConnection(); String sql = "update user set password='"+pass+"' where userId="+id; st = conn.createStatement(); int row = st.executeUpdate(sql); if(row>0){ flag = true; } } catch (SQLException e) { e.printStackTrace(); }finally{ DBConnection.closeAll(st, conn); } return flag; } }