结果集开始前 (SQLException)

Question

嘿，我似乎不明白为什么我的代码会抛出这个 SQLException：

java.sql.SQLException: 在结果集开始之前

这部分代码的目的是获取mySQL数据库中保存的密码，并与输入的密码进行比较。

public static boolean isPasswordMatching(String user, String pass) throws Exception{
    
    boolean areMatching = true;
    
    try {
        
        Class.forName(driver);
        
        //the query I want to execute
        String myQuery = "SELECT user_password FROM myData WHERE user_id = \"" + user + "\"";

        java.sql.Connection connection  =  DriverManager.getConnection(url,username,password);
        Statement stmt = connection.createStatement();

        ResultSet rs = stmt.executeQuery(myQuery);// <<== Result Set (WHAT SEEMS TO BE THE PROBLEM)
        String rightPassword = rs.getString("user_password");
        
        System.out.println("successfully checked passwords");

        //makes areMatching true if passwords match, else, it will be false
        if (pass == rightPassword) {areMatching = true;} else {areMatching = false;};

        //cleanup
        connection.close();
        return areMatching;
        
    }catch(SQLException se) {System.out.println("SE encountered a problem while trying to connect : "+ se);
    }catch(Exception e) {System.out.println("encountered a problem while trying to connect : "+e);};
    
    //return statement (boolean)
    return areMatching;
}

Answer 1

在获取数据之前，您需要使 resultset 指向第一个元素：

...
String rightPassword = "";
if(rs.next()) {
rightPassword = rs.getString("user_password");
}
...