如何在Java-mysql中驗證用戶名和密碼？

Question

如何以最正確的方式驗證用戶輸入數據庫的用戶名和密碼？

In c++, we used to verify by using if-else:
    if((user == "username")&&(pass == "password")){
             cout<<"You are now logon!";
    }

在java-mysql中我不確定我是否在正確的軌道上：

登錄按鈕

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:

        user = jTextField1.getText();
        pass = jPasswordField1.getPassword();
        login();
}

方法/函數

private void login() {

        try {
                if (user != null) {
                sql = "Select * from users_table Where username='" + user + "'";
                rs = stmt.executeQuery(sql);

                rs.next();
                username = rs.getString("username");
                password = rs.getString("password");

            }
        } 
    catch (SQLException err) {
            JOptionPane.showMessageDialog(this, err.getMessage());
        }

}

如果用戶輸入的用戶名和密碼與數據庫中的用戶名和密碼匹配，那么他將被定向到新的jFrame else消息對話框將彈出說無效的用戶名或密碼。 有人可以幫助我使用我的代碼，我不知道如何使用mysql的if-else語句;

謝謝！ :)

Answer 1

實現以下代碼：

private void login() {
    try {
        if (user != null && pass != null) {
            String sql = "Select * from users_table Where username='" + user + "' and password='" + pass + "'";
            rs = stmt.executeQuery(sql);
            if (rs.next()) {
                //in this case enter when at least one result comes it means user is valid
            } else {
                //in this case enter when  result size is zero  it means user is invalid
            }
        }

        // You can also validate user by result size if its comes zero user is invalid else user is valid

    } catch (SQLException err) {
        JOptionPane.showMessageDialog(this, err.getMessage());
    }

}

Answer 2

• 始終將Hash加密密碼存儲在數據庫中，有關加密密碼的詳細信息，請參閱JASYPT
• 加密用戶輸入的密碼並比較兩個加密密碼
• 查詢數據庫時使用參數化查詢

Answer 3

你不必再對mySQL做任何事了。 您已擁有憑據。 一個例子：

if ((user.equals(username)) && (pass.equals(password))) {
   JFrame newFrame = new JFrame();
} else {
   JOptionPane.showMessageDialog(null, "alert", "alert", JOptionPane.ERROR_MESSAGE); 
}

Answer 4

使用預准備語句以及像DButils這樣的庫可以大大簡化您的工作。

另外，不要使用替換傳遞參數，例如select name from members where code =? 。 如果您有許多參數，請創建一個對象數組並將它們傳遞給對象數組，例如Objects[] parms = {code1,code2} 。

Answer 5

if (username.length()>0 && password.length()>0)
{
    String query = "Select * from adminlogin Where Username='" + username + "' and Password='" + password + "'";

    rs = sta.executeQuery(query);

   if (rs.next()) 
   {

        home hme=new home();
        this.setVisible(false);
        hme.setVisible(true);
   } 
   else 
   {
       JOptionPane.showMessageDialog(null,"username and password are wrong ");
   }
}
else
{
      JOptionPane.showMessageDialog(null,"please field username and password ");
}