JDBC工具类

java中对sql进行操作时产生了大量重复的代码，于是可以将这些重复的代码添加到一个工具类中去，简化代码的书写过程。
1.注册驱动
2.抽取一个方法获取连接对象 需求，不传递参数，静态代码块，配置文件
jdbc.properties
url=
user=
password=

util代码

static String url;
static String user;
static String password;
static String driver;



/*静态代码块*/
static {
    try {
        Properties pro = new Properties();
        //获取src路径下文件的方法 Classloader
        ClassLoader classLoader = JDBCuUtils.class.getClassLoader();
        URL res =classLoader.getResource("jdbc.properties");
        String path = res.getPath();

       pro.load(new FileReader(path));
        url = pro.getProperty("url");
        user = pro.getProperty("user");
        password = pro.getProperty("password");
        driver = pro.getProperty("driver");
        try {
            Class.forName(driver);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}
public static Connection getConnection() throws SQLException {
    return DriverManager.getConnection(url,user,password);
}

/*执行增删改查语句时要关闭stmt和conn两个对象*/
public static void close(Statement stmt, Connection conn) {

    if (stmt != null) {
        try {
            stmt.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    if (conn != null) {
        try {
            conn.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

/*执行查询语句时要关闭stmt,conn和rs三个对象,按照从小到大关闭资源*/
public static void close(Statement stmt, Connection conn, ResultSet rs) {
    if (rs != null) {
        try {
            rs.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    if (stmt != null) {
        try {
            stmt.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    if (conn != null) {
        try {
            conn.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

}