How to check if email already exists in DB - JPA, Java, JBoss

Question

I am trying to check if the email the user enters already exists in the db. I have to methods (register and update) and one helper method in my UserBean.java:

    public String register() {
        if (emailAlreadyExists(this.user.getEmail())) {
            FacesContext.getCurrentInstance().addMessage(null,
                    new FacesMessage("This e-Mail is already in use."));
        } else {
            this.conversation.end();
            try {
                if (this.id == null) {
                    this.entityManager.persist(this.user);
                    return "thanks.xhtml";
                } else {
                    this.entityManager.merge(this.user);
                    return "thanks.xhtml";
                }
            } catch (EJBTransactionRolledbackException e) {
                Throwable t = e.getCause();
                while ((t != null)
                        && !(t instanceof ConstraintViolationException)) {
                    t = t.getCause();
                }
                if (t instanceof ConstraintViolationException) {
                    FacesContext.getCurrentInstance().addMessage(null,
                            new FacesMessage(e.getMessage()));
                    return null;
                }
            }
        }
        return null;
    }

    public String update() {
            if (emailAlreadyExists(this.user.getEmail())) {
                FacesContext.getCurrentInstance().addMessage(null,
                        new FacesMessage("This e-Mail is already in use."));
            } else {
                this.conversation.end();
                try {
                    if (this.id == null) {
                        this.entityManager.persist(this.user);
                        return "search?faces-redirect=true";
                    } else {
                        this.entityManager.merge(this.user);
                        return "view?faces-redirect=true&id=" + this.user.getId();
                    }
                } catch (Exception e) {
                    FacesContext.getCurrentInstance().addMessage(null,
                            new FacesMessage(e.getMessage()));
                    return null;
                }
            }
            return null;
        }

public boolean emailAlreadyExists(String emailAddr) {
        long counter = 0;
        counter = (Long) this.entityManager
                .createQuery(
                        "SELECT COUNT(u.email) FROM User u WHERE u.email = :email")
                .setParameter("email", emailAddr).getSingleResult();
        if (counter > 0) {
            return true;
        }
        return false;
    }

I don't know why but this code works perfect for the register method (whenever I enter an existing email address), but not for the update method, although they are very similar. Every time when I perform an user update, these SQL statements are performed in the following order (should be in reverse order):

22:44:20,865 INFO  [stdout] (http-localhost-127.0.0.1-8080-1) Hibernate: update User set  country=?, email=?, firstName=?, lastName=?, password=?, phone=?, postalCode=? where id=?
22:44:20,875 INFO  [stdout] (http-localhost-127.0.0.1-8080-1) Hibernate: select count(user0_.email) as col_0_0_ from User user0_ where user0_.email=? limit ?

I already debugged the code and recognised that the update statement is executed on that line:

counter = (Long) this.entityManager
            .createQuery(
                    "SELECT COUNT(u.email) FROM User u WHERE u.email = :email")
            .setParameter("email", emailAddr).getSingleResult();

Any help would be greatly appreciated.

Answer 1

You've got a stale entity resulting of a transaction nightmate between JPA and your session bean. You've got to change your User entity lifecycle and make appropriate changes on your JPA transaction management.