JDBC -数据库导入-第二版-2023-2-25

1、配置资源文件 .properties (driver, url,username,password) 便于后期更改

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/shop?useUnicode=true&characterEncoding=utf8&useSSL=false
username=root
password=123456

2、编写utils 工具类，读取配置资源，加载数据库 ，关闭资源这些操作只要连接上了，基本上不需要再重复写代码。

public class JdbcUtils {

    private static String dirver =null;
    private static String url =null;
    private static String username =null;
    private static String password =null;

    static {
        //从db.properties中获取用户信息和url
        try {
            InputStream in = JdbcUtils.class.getClassLoader().getResourceAsStream("db.properties");
            Properties properties = new Properties();
            properties.load(in);

            dirver = properties.getProperty("driver");
            url = properties.getProperty("url");
            username = properties.getProperty("username");
            password = properties.getProperty("password");

            //1.驱动只用加载一次
                Class.forName(dirver);
        } catch (Exception e) {
            e.printStackTrace();
            }
        }

        //获取连接
        public static Connection getConnection() throws SQLException {
            return DriverManager.getConnection(url,username,password);
        }

       //释放连接资源
       public static void release(Connection conn, Statement st, ResultSet rs){
        if (rs!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (st!=null){
            try {
                st.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (conn!=null){
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
       }

    }

3、编写数据库的增，删，改，查 主程序

3.1 删除

public class JdbcDelete {
    public static void main(String[] args) {
        Connection conn = null;
        Statement st =null;
        ResultSet rs =null;

        try {
            conn = JdbcUtils.getConnection();
            st = conn.createStatement();
            String sql = "DELETE FROM account WHERE id =3";
            int i = st.executeUpdate(sql);
            if (i>0){
                System.out.println("删除成功！");
            }

        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.release(conn,st,rs);
        }
    }

}

3.2 插入

public class TestInsert {
    public static void main(String[] args) {
        Connection conn = null;
        Statement st =null;
        ResultSet rs =null;

        try {
            conn = JdbcUtils.getConnection();
            st = conn.createStatement();
            String sql = "INSERT INTO account(id,`name`,`money`)\n" +
                    "VALUES(3,'CC','20000.00')";
            int i = st.executeUpdate(sql);
            if (i>0){
                System.out.println("插入成功！");
            }

        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
           JdbcUtils.release(conn,st,rs);
        }
    }
}

3.3 更改 更新

public class JdbcUpdate {
    public static void main(String[] args) {
        Connection conn = null;
        Statement st =null;
        ResultSet rs =null;

        try {
            conn = JdbcUtils.getConnection();
            st = conn.createStatement();
            String sql = "UPDATE account SET `name`='AAAA',`money`='50000.00' WHERE id=1";
            int i = st.executeUpdate(sql);
            if (i>0){
                System.out.println("更新成功！");
            }

        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.release(conn,st,rs);
        }
    }
}

3.4 查询 （executeQuery）

public class JdbcSelect {
    public static void main(String[] args) {
        Connection conn = null;
        Statement st = null;
        ResultSet rs = null;

        try {
            conn = JdbcUtils.getConnection();
            st = conn.createStatement();

            //sql
            String sql = "SELECT * from account where id =1";
            rs = st.executeQuery(sql);
            while (rs.next()){
                System.out.println(rs.getString("name"));;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.release(conn,st,rs);
        }
    }
}