JDBC-Demo

• 获取数据库连接

public class JDBCUtils {

	//使用的是mysql-connection-java-8.0.12.jar 
	//mysql-connection-java-5.x url="jdbc:mysql://localhost:3306/dbname"
    private static String url = "jdbc:mysql://localhost:3306/demo1?useUnicode=true&characterEncoding=utf8&useSSL=true&serverTimezone=UTC&zeroDateTimeBehavior=CONVERT_TO_NULL";
    private static String password = "your password";
    private static String user = "youname";

    public static Connection getConnection(){

        try {
            //使用什么驱动连接数据库 注册驱动 抛出异常
            Class.forName("com.mysql.cj.jdbc.Driver");
            //建立与数据库的连接  驱动管理器DriverManager
            return  DriverManager.getConnection(url, user, password);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

	 public static void close(ResultSet result, Statement stmt,Connection con){
        try {
            if (result != null) {
                result.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        try {
            if (stmt != null) {
                stmt.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        try {
            if (con != null) {
                con.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

• 数据库查询

 public static void selectAll() {
        //Connection 与一个特定的数据库连接(会话)。
        Connection con = null;
        //Statement 用于执行一个静态SQL语句的对象并返回它产生的结果。
        Statement stmt = null;
        //ResultSet 代表一个数据库表的数据结果集,通常由执行一个语句查询数据库。
        ResultSet result = null;
        try {
            con = JDBCUtils.getConnection();
            //发起请求
            stmt = con.createStatement();
            //executeQuery(String sql )执行给定的SQL语句,它返回一个 ResultSet对象。
            result = stmt.executeQuery("select * from user");

            while (result.next()) {
//                System.out.println(result.getInt(1) + "," + result.getString(2) + "," + result.getString(3)); //通过列索引获取
                //通过列标签columnLabel 列标签
                System.out.println(result.getInt("id") + "," + result.getString("username") + "," + result.getString("password"));
            }
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            JDBCUtils.close(result, stmt, con);
        }

    }

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