Question

So I have this username and password validation code using Java persistence.

public Subscriber validateLogin(String username, String password)
{
   EntityManager em = getEntityManager();

    Query q = em.createQuery("SELECT s FROM Subscriber s WHERE s.username = :username OR s.password = :password ");

    q.setParameter("username", username);
    q.setParameter("password", password);

    try
    {
        return (Subscriber) q.getSingleResult();
    }
    catch (Exception e)
    {
        return null;
    }
}

So I check if the subscriber return anything or null. Here is my code:

private void jButton3ActionPerformed(java.awt.event.ActionEvent evt)
{
    // TODO add your handling code here:
    SubscriberJpaController sjc = new SubscriberJpaController();
    Subscriber sub = sjc.validateLogin(jTextField1.getText(), jPasswordField1.getText());

    System.out.println(sub);
}

and it returns null. Anything wrong with my code or logic?

Answer 1

there might be an exception thrown when you do the query. you have to print the stacktrace to see the cause.

I guess (not sure) the problem could be at the line q.getSingleResult(); if other configurations were correctly set.

Jpa is expecting a unique result. however your query could generate a set of Subscribers by username=.. or password=…. e.g.

user a(uname,pwd)= ("usera","123")
user b(uname,pwd)= ("userb","123")

so the method getSingleResult() throws the exception.

also, you may consider to use jpa TypedQuery with generic instead of doing the class casting manually.