java将从数据库检索到的数据分配给字符串变量
我正在制作一个系统,用于验证数据库中已经定义的凭据和jTextfield中输入的凭据。当我在if-else语句中输入条件时,它表示不能将字符串转换为布尔值。请帮忙
Connection con = (Connection) DriverManager.getConnection (host, uName, uPass);
Statement stmt = (Statement) con.createStatement ();
//login is a table in my database,password a tuple
String SQL = "SELECT password FROM login;";
ResultSet password = stmt.executeQuery (SQL);
String pass = adminpassword.getText();
String sqlpass = password.getString("password");
//error shows on if else below
if(sqlpass = pass){
JOptionPane.showMessageDialog(null,"You have entered an incorrect password,please try again.","Incorrect Password",JOptionPane.WARNING_MESSAGE);
}
else{
String passconfirm = "SELECT admin_id WHERE password = 77353";
ResultSet confirmpass = stmt.executeQuery(passconfirm);
JOptionPane.showMessageDialog(null,"Welcome","Welcome " + confirmpass,JOptionPane.INFORMATION_MESSAGE);
Countyinfo proceed = new Countyinfo();
proceed.setVisible(true);
}
}
catch(SQLException err){
System.out.println (err.getMessage());
};
# 1 楼答案
在
if
语句表达式中有一个赋值,它返回的是String
,而不是所需的boolean
应该是
比较
Strings
(操作符==
比较Object
引用而不是内容)# 2 楼答案
相等的布尔运算符是
==
,而不是=
(赋值运算符)。赋值操作的计算结果将始终为分配给其左值的值这就是为什么
sqlpass = pass
的计算结果为String
。sqlpass == pass
将计算为boolean
编辑: 不过,比较
String
的标准方法是使用如下.equals
方法:if(sqlpass.equals(pass))