JPA string comparison

Question

I've written a simple login system using a JPQL query, which always returns no result:

public boolean check(String name, String password) {
    final String qstring="SELECT e FROM Muser e WHERE e.name = '"+name+"'";
    Muser user;
    try{
        user = em.createQuery(qstring, Muser.class).getSingleResult();  
    }
    catch(NoResultException e){
        return false;
    }
    return password.equals(user.getPassword());
}

When I changed it to a native query:

user = (Muser) em.createNativeQuery(qstring, Muser.class).getSingleResult();

or an int expression:

final String qstring="SELECT e FROM Muser e WHERE e.id = "+id; 

It goes all right. What's the problem? Thanks a million!

Solution 1

It might be a problem with string comparison in your JPA provider. Do you test it on the case-sensitive data?

You could also try (and it's the preferred way) using parameters instead of crafting your statement by hand. It's not only safer (prevents SQL injection) but also faster: not only for Java (you don't concatenate Strings) but also for the DB (the query can be prepared once for all executions). It might be something like this:

final String qstring = "SELECT e FROM Muser e WHERE e.name = :name";
TypedQuery<Muser> query = em.createQuery(qstring, Muser.class);
query.setParameter("name", name);
user = query.getSingleResult();

Solution 2

I think problem is because of String comparison.My solution to this problem is:
using lowercase for comparison.

final String qstring = "SELECT e FROM Muser e WHERE LOWER(e.name) = :name";
TypedQuery<Muser> query = em.createQuery(qstring, Muser.class);
query.setParameter("name", name.toLowerCase());
user = query.getSingleResult();