private void testCrud() {
     Connection conn = null;      //連接對(duì)象
     PreparedStatement pstmt = null;  //預(yù)編譯的SQL語句對(duì)象
      try{
        //加載MySQL驅(qū)動(dòng)程序
        Class.forName("com.mysql.jdbc.Driver");
        //連接字符串
        String url = "jdbc:mysql://localhost:3306/test";
        //建立數(shù)據(jù)庫連接
        conn = DriverManager.getConnection(url,"root","");
        //設(shè)置事務(wù)的隔離級(jí)別
        // conn.setTransactionIsolation(Connection. TRANSACTION_REPEATABLE_READ);
        //設(shè)置自動(dòng)提交為false，開始事務(wù)
        conn.setAutoCommit(false);
        //帶參數(shù)的更新語句
        String sql = "INSERT INTO user_info (username ,password ,age )values(?,?,?)";
        //準(zhǔn)備語句
        pstmt = conn.prepareStatement(sql);
        //綁定參數(shù)，執(zhí)行更新語句，將張三的賬戶金額減去1000元
        pstmt.setString(1, "zhangui");
        pstmt.setString(2, "1111");
        pstmt.setInt(3, 300);
        pstmt.execute();
        
        //綁定參數(shù)，執(zhí)行更新語句，將李四的賬戶金額增加1000元
        // pstmt.setString(1, "zzzzzzzzzzzzzzzzz"); //綁定了非法參數(shù)
        //pstmt.setString(2, "1111111111");
        //pstmt.setInt(3, 500);
        //pstmt.execute(); //將拋出SQL異常
        //提交事務(wù)
        //conn.commit();
        System.out.println("事務(wù)已提交，轉(zhuǎn)賬成功！");
        //關(guān)閉語句、連接
        pstmt.close(); conn.close();
      }catch(Exception e){
        try{
          conn.rollback();  //回滾事務(wù)
          System.out.println("事務(wù)回滾成功，沒有任何記錄被更新！");
        }catch(Exception re){
          System.out.println("回滾事務(wù)失??！");
        }
        e.printStackTrace();
      }finally{
        if(pstmt!=null) try{pstmt.close();}catch(Exception ignore){}
        if(conn!=null) try{conn.close();}catch(Exception ignore){}
      }
    
  }