taxratedaobean.java

想学习EJB的同学

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package ejb3.day6;

import javax.ejb.Stateless;
import javax.persistence.Query;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

/**
 *
 * @author user
 */
@Stateless
public class TaxRateDaoBean implements TaxRateDaoLocal {
    @PersistenceContext
    private EntityManager em;
    
    public void doSomeStuff() {
        TaxRate tr = new TaxRate("Beijing", 0.08);
        em.persist(tr);
        tr = new TaxRate("Shanghai", 0.075);
        em.persist(tr);
        tr = new TaxRate("Tianjin", 0.06);
        em.persist(tr);
        tr = new TaxRate("Chongqing", 0.05);
        em.persist(tr);
    }

    public double getTaxRate(String province) {
        Query q = em.createNamedQuery("findByProvince");
        q.setParameter("province", province);
        TaxRate tr = (TaxRate)q.getSingleResult();
        if(tr != null) return tr.getRate();
        return 0.0;
    }

    
}