Are javax.persistence.Query objects cachable?

I'm writing a stateless EJB. I had methods like:

public String getXxx(final String userId) throws ... {
    final Query query = em.createNativeQuery(...);
    query.setParameter(1, userId);
    return (Str开发者_如何学Pythoning)query.getSingleResult();
}

Can I cache the Query object instantiating it at load time and using it in a multi-thread environment?

private static final Query query = em.createNativeQuery(...);
public String getXxx(final String userId) throws ... {
    query.setParameter(1, userId);
    return (String)query.getSingleResult();
}

Thanks.

No, you cannot. Query is created by (and references) a particular EntityManager instance which is:

1. Not thread-safe.
2. Should not be held onto for prolonged periods of time.

I think ChssPly76 is right. But you should maybe look at NamedQueries. Maybe this is something in the direction your looking.

However, you can make the query String itself class-instantiated. This will save you a nanosecond here and there.

Here's a greatly simplified example (I apologize for any syntax or other errors):

private static final String sqlMyQuery =
    "SELECT stu FROM Student stu " +
    "WHERE stu.zipCode = ?1 " +
    "AND stu.status = ?2";

public static Student getStudentByZipAndStatus(String zip, int status) {
    Student student = em.createNativeQuery(sqlMyQuery)
        .setParameter(1, zip)
        .setParameter(2, status)
        .getSingleResult();

    return (student);
}