java - Else 语句不在 SQL 数据库的 while 循环内执行

Question

Else 语句在 while 循环内不起作用

public void loginButton() throws ClassNotFoundException, SQLException{
        Class.forName("com.mysql.jdbc.Driver");
        Connection con = (Connection) DriverManager.getConnection("jdbc:mysql://localhost:3306/finditdb","root","root");
        Statement stmt = con.createStatement();
        String usernameInput = usernameField.getText();
        String passwordInput = passwordField.getText();
        ResultSet rs = stmt.executeQuery("SELECT * FROM finditdb.login WHERE username like '" + usernameInput +"' and password like '" + passwordInput +"'");
        while(rs.next()){
            String usernameDb = rs.getString("username");
            String passwordDb = rs.getString("password");
            if(usernameInput.equals(usernameDb) && passwordInput.equals(passwordDb)){
                System.out.println("Access Granted..");
            }
            else {
                System.out.println("Access denied..");
            }
        }
    }

Answer 1

You could try this and let me know if it works the way you want it to.

while(true){     
     if(rs.next()){
        String usernameDb = rs.getString("username");
        String passwordDb = rs.getString("password");
        if(usernameInput.equals(usernameDb) && passwordInput.equals(passwordDb)){
            System.out.println("Access Granted..");
            break;
          }

     }

     else{
            System.out.println("Access denied..");
            break;
     }
    }

我们没有在 while 循环 括号内提到任何退出条件，因此循环将继续运行，直到没有更多记录可供提取(否则将打印 Access Denied 并中断)或者如果授予访问权限(再次中断)。