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一开始步骤如下： 

1. 一开始导入mysql.jar的包到项目库里，项目结构

2. 封装一个sql连接库类

        a:  获取驱动String dirver = "com.mysql.cj.jdbc.Driver";

        b:  获取.jar路径String url = "jdbc:mysql://localhost:3306/humanresourcesystem?useSSL=false";

        c:  其中mysql是要连接的数据库管理器（app）,localhost:3306是本地主机（127.0.0.1），humanresourcesystem是数据库名称，useSSL=false加一层没找到情况，不然可能会报错。 获取用户、密码 String user = "root"; String pwd = "xxxx";

3.   加载驱动Class.forName(dirver)需要抛异常

4.   建立连接Connection conn = DriverManager.getConnection(url,user,pwd);需要抛异常

创建一个类，名字随意！！

public static Connection conn = null;
    private static final String driver ="com.mysql.cj.jdbc.Driver";
    private static final String url = "jdbc:mysql://localhost:3306/statusdata?useSSL=false";
    private static final String user = "root";
    private static final String pwd = "123lgk";
    //建立连接
    public static void ConnectJdbc()
    {
        try {
            Class.forName(driver);
            conn = DriverManager.getConnection(url, user, pwd);
        }catch (Exception ex)
        {
            System.out.println("错误信息：" + ex.getMessage());
        }
    }
    //变量全肯定的增删改
    public static Statement getStatement()throws Exception
    {
        ConnectJdbc();
        return conn.createStatement();
    }
    //变量未知但后赋值的增删改
    public static PreparedStatement getPreStatement(String sql)throws Exception
    {
        ConnectJdbc();
        return conn.prepareStatement(sql);
    }
    //变量全肯定的查询
    public static ResultSet getSta_ResultSet(String sql) throws Exception
    {
        return getStatement().executeQuery(sql);
    }
    //变量未知但后赋值的查询
    public  static  ResultSet getPre_ReResultSet(PreparedStatement ps) throws Exception
    {
        return ps.executeQuery();
    }

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