Java与SQL登录相关

Question

当我登录时，一切都很完美。但是当我输入一个不存在的帐户时，消息对话框会根据数据库中的帐户数量循环显示。我相信这是因为我使用了 while(rss.next()) 。这是我的代码:

try {
    if(e.getSource()==loginButton){
        int count = 1;
        conn=DriverManager.getConnection("jdbc:sqlserver://localhost:1433;databaseName=login_DB;integratedSecurity=true");
        st=conn.createStatement();
        rss=st.executeQuery("select * from tblLogin");
        while(rss.next()){
            String user = rss.getString(1);
            String pass = rss.getString(2);
            if(usernameTF.getText().equals(user)&&passwordTF.getText().equals(pass)){
                JOptionPane.showMessageDialog(null,"YEAAAA");
            }//if success

            else {
                JOptionPane.showMessageDialog(null,"Account doesn't exist! Please try again.");
            }
        }//while
    }//getsource loginButton

Answer 1

做这样的事情..

int flag = 0;
if(usernameTF.getText().equals(user) && passwordTF.getText().equals(pass))
{
    flag=1; // if found then, value change to 1 otherwise it will be 0
}

//Now, put below condition after while loop
if (flag==1) {
    JOptionPane.showMessageDialog(null,"YEAAAA");
}
else {
    JOptionPane.showMessageDialog(null,"Account doesn't exist! Please try again.");                
}

或

正如 @Thilo 建议的那样，您可以在 SELECT 查询中使用 WHERE 子句。