Question

我正在尝试检查用户输入的电子邮件是否已存在于数据库中。我必须在UserBean.java中使用方法（注册和更新）和一个帮助方法：

    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;
    }

我不知道为什么，但这段代码适用于注册方法（无论何时我输入现有的电子邮件地址），但不适用于更新方法，尽管它们非常相似。每次执行用户更新时，这些SQL语句都按以下顺序执行（应按相反顺序）：

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 ?

我已经调试了代码，并认识到在该行上执行了update语句：

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

非常感谢任何帮助。

Answer 1

您有一个陈旧的实体，导致JPA和您的会话bean之间的交易夜友。您必须更改用户实体生命周期并对JPA事务管理进行适当的更改。

如何检查数据库中是否已存在电子邮件 - JPA，Java，JBoss

1 个答案: