package com.czb.util;

import java.sql.*;
import java.util.*;

public class DButil {
    private static DButil myDButil = new DButil();
    private DButil(){

    }
    public static DButil getMyDButil(){
        return myDButil;
    }
    private static String driver = "com.mysql.jdbc.Driver";
    private static String url = "jdbc:mysql://localhost:3306/mydb?useSSL=false&serverTimezone=UTC&characterEncoding=utf8";
    private static String username = "root";
    private static String password = "root";
    private static Connection conn;
    private static PreparedStatement ps;
    private static ResultSet rs;
    static {
        try {
            Class.forName(driver);
            System.out.println("加载驱动成功");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    public List<Map> select(String sql,Object...objs){
        List<Object> objects = Arrays.asList(objs);
        List<Map> list = new ArrayList<>();
        try {
            conn = DriverManager.getConnection(url,username,password);
            ps = conn.prepareStatement(sql);
            for (int i = 0; i < (sql+" ").split("\\?").length-1; i++) {
                 ps.setObject(i+1,objects.get(i));
            }
            rs = ps.executeQuery();
            //ResultSetMetaData 类
            //可用于获取关于 ResultSet 对象中列的类型和属性信息的对象：
            ResultSetMetaData metaData = rs.getMetaData();
            while (rs.next()){
                Map map = new HashMap();
                for (int i = 1; i <= metaData.getColumnCount(); i++) {
                    String key = metaData.getColumnName(i);
                    map.put(key,rs.getObject(key));
                }
                list.add(map);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            close();
        }
        return  list;
    }
    public int update(String sql,Object...objs){
        List<Object> objects = Arrays.asList(objs);
        int is = 0;
        try {
            conn = DriverManager.getConnection(url,username,password);
            ps = conn.prepareStatement(sql);
            for (int i = 0; i < (sql+" ").split("\\?").length-1; i++) {
                 ps.setObject(i+1,objects.get(i));
            }
            is = ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            close();
        }
        return is;
    }
    public static void close(){
        try {
            if(conn != null)conn.close();
            if(ps != null)ps.close();
            if(rs != null)rs.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}