Java - 未捕获异常

Question

This is the exception I created

public class UserNaoExiste extends Exception {

    public UserNaoExiste(){
        super("User não existe");
    }

}

This is the function where the exception is thrown (it is in fact thrown, I believe)

public Entidades.User getUser(String username) throws Exceptions.UserNaoExiste {
        Entidades.User u = null;
        try (Connection con = DriverManager.getConnection(this.url, this.username, this.password)) {
            PreparedStatement stm = con.prepareStatement("SELECT * FROM user WHERE username = ?");
            stm.setString(1, username);
            ResultSet rs = stm.executeQuery();
            if (rs.next() == false) {
                throw new Exceptions.UserNaoExiste();
            }
            u = new Entidades.User(rs.getString("Username"), rs.getString("Password"), rs.getString("Nick"), rs.getString("Admin"));
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }

        return u;
    }

This is where the exception SHOULD be caught

private String login(String username, String password) {
        Entidades.User u = null;
        String r = "s";
        try {
            u = udao.getUser(username);
            System.out.println("olaola");
        } catch (Exception e) {
            r = "n";
        }

        System.out.println(r);
        System.out.flush();

        if (r.equals("s") && u.checkPassword(password)) {
            this.user = u;
            this.auth = (u.isAdmin() ? 2 : 1);
        } else {
            r =  "n";
        }
        return r;
    }

What actually happens is the exception is thrown, but very happily ignored, that println executes, r is not set to "n", and then it tries to do u.checkPassword on a null. I've never been so confused in my life while coding. Any help is appreciated

Answer 1

Inside getUser method, the UserNaoExiste exception is thrown and it is caught inside that same method.

try (Connection con = DriverManager.getConnection(this.url, this.username, this.password)) {
        PreparedStatement stm = con.prepareStatement("SELECT * FROM user WHERE username = ?");
        stm.setString(1, username);
        ResultSet rs = stm.executeQuery();
        if (rs.next() == false) {
            throw new Exceptions.UserNaoExiste();
        }
        u = new Entidades.User(rs.getString("Username"), rs.getString("Password"), rs.getString("Nick"), rs.getString("Admin"));
    } catch (Exception e) {
        System.out.println(e.getMessage());
    }

And in the login method the catch statement will never execute because the exception throw by getUser is already caught by that getUser method.

You can catch a specific exception SQLException for database related exceptions instead of Exception inside your getUser method.