JDBC

JDBC: Java Database Connectivity SUN 公司提供的一套操作數(shù)據(jù)庫(kù)的標(biāo)準(zhǔn)規(guī)范。

一、 JDBC與數(shù)據(jù)庫(kù)驅(qū)動(dòng)

接口與實(shí)現(xiàn)的關(guān)系

二奇钞、JDBC規(guī)范(掌握四個(gè)核心對(duì)象)

1. DriverManager : 注冊(cè)驅(qū)動(dòng)
2. Connection：與數(shù)據(jù)庫(kù)進(jìn)行連接
3. Statement： 操作數(shù)據(jù)庫(kù)SQL語(yǔ)句的對(duì)象
4. ResultSet： 結(jié)果集或者一張?zhí)摂M表

 public static void main(String[] args) throws SQLException {
        System.out.println("test jjjjDemo");
        Connection con = null;
        DriverManager.registerDriver(new com.mysql.jdbc.Driver());
        Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb2", "root", "password");
        Statement stmt = conn.createStatement(); // 得到執(zhí)行SQL的對(duì)象
        ResultSet rs = stmt.executeQuery("select * from employee");
        while (rs.next()) {
            System.out.println(rs.getObject(1)); // 訪問(wèn)數(shù)據(jù)庫(kù)的第一列
            System.out.println(rs.getObject(2)); // // 訪問(wèn)數(shù)據(jù)庫(kù)的第二列
            System.out.println(rs.getObject(3));
            System.out.println(rs.getObject(4));
            System.out.println(rs.getObject(5));
            System.out.println(rs.getObject(6));
            System.out.println(rs.getObject(7));
            System.out.println(rs.getObject(8));
            System.out.println("================================");
        }
        // 結(jié)果集關(guān)閉 釋放支援
        rs.close();
        stmt.close();
        conn.close();
    }

DriverManager 優(yōu)缺點(diǎn)

導(dǎo)致注冊(cè)兩次
強(qiáng)烈依賴數(shù)據(jù)庫(kù)的驅(qū)動(dòng) jar

DriverManager.registerDriver(new com.mysql.jdbc.Driver()); 

 public Driver() throws SQLException {

    }
    // 靜態(tài)代碼塊隨著類的加載而加載忽刽，導(dǎo)致注冊(cè)兩側(cè)
    static {
        try {
            DriverManager.registerDriver(new Driver());
        } catch (SQLException var1) {
            throw new RuntimeException("Can't register driver!");
        }
    }

改為直接加載驅(qū)動(dòng)

  public static void main(String[] args) throws SQLException, ClassNotFoundException {
        System.out.println("test jjjjDemo");
        Connection con = null;
        //DriverManager.registerDriver(new com.mysql.jdbc.Driver());
        Class.forName("com.mysql.jdbc.Driver"); // 加載驅(qū)動(dòng)(反射)
        Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb2", "root", "password");
        Statement stmt = conn.createStatement(); // 得到執(zhí)行SQL的對(duì)象
        ResultSet rs = stmt.executeQuery("select * from employee");
        while (rs.next()) {
            System.out.println(rs.getObject(1));
            System.out.println(rs.getObject(2));
            System.out.println(rs.getObject(3));
            System.out.println(rs.getObject(4));
            System.out.println(rs.getObject(5));
            System.out.println(rs.getObject(6));
            System.out.println(rs.getObject(7));
            System.out.println(rs.getObject(8));
            System.out.println("================================");
        }
        // 結(jié)果集關(guān)閉 釋放支援
        rs.close();
        stmt.close();
        conn.close();
    }

URL：SUN 公司與數(shù)據(jù)庫(kù)廠商之間的協(xié)議

協(xié)議 子協(xié)議       IP           端口號(hào)   數(shù)據(jù)庫(kù)
jdbc: mysql: // localhost:  3306     /mydb2