1

我有一个类 User，它充当数据库中用户表的持久性模型：

public class User {
@Id
@Basic(optional = false)
@Column(name = "USER_ID")
private Long userId;

@JoinColumn(name = "LAST_CHANGED_USER_ID", referencedColumnName = "USER_ID")
@ManyToOne(fetch = FetchType.LAZY)
private User lastChangedUser;
...

@Override
public int hashCode() {
    int hash = 0;
    hash += (userId != null ? userId.hashCode() : 0);
    return hash;
}

@Override
public boolean equals(Object object) {
    if (!(object instanceof User)) {
        return false;
    }

    User other = (User) object;
    if ((this.userId == null && other.userId != null) || 
        (this.userId != null && !this.userId.equals(other.userId))) {
        return false;
    }
    return true;
}

@Override
public String toString() {
    return "User[userId=" + userId + "]";
}
}

每当对 User 实例进行更改时，都会更新字段 lastChangedUser。考虑以下方法：

private void setUsername(string username, User lastChangedUser){
    this.username = username;
    this.lastChangedUser = lastChangedUser;
}

public void updateUserName(Long userId, Long lastChangedUserId, String username){
    EntityManager em = PersistenceManager.getPersistenceManager()
       .getEntityManager();
    EntityTransaction transaction = em.getTransaction();

    User user = em.find(User.class, userId);
    User lastChangedUser = em.find(User.class, lastChangedUserId);

    transaction.begin();
    user.setUsername(username, lastChangedUser);
    transaction.commit();
}

和单元测试：

public void testUpdateUsername(){
    UserFacade instance = new UserFacade();
    User john = instance.getUserByUserId(new Long(1));
    User jane = instance.getUserByUserId(new Long(2));

    // make the update and persist
    instance.updateUsername("JANE M. DOE", jane.userId, john.userId);

    // assert that john made the change to jane
    jane = instance.getUserByUserId(new Long(2));

    assertTrue(jane.username.equals("JANE M. DOE"));

    User actual = jane.lastChangedUser;
    User expected = john;

    // this assertion passes...
    assertTrue(actual.equals(expected));

    // yet this assertion fails!
    assertTrue(expected.equals(actual));

    // this fails as well.
    assertEquals(expected, actual);
}

使用 Netbeans 7.1.1，测试结果屏幕返回错误消息：

FAILED: expected: User[id=1], but was: User[id=1].

经检查，该对象actual不是 type User，而是 Proxy 对象的类型。我认为这是由于 LAZY fetch 注释。因此，对象的 userid 的值为null并expected.equals(actual)返回false。然而，actual.equals(expected)回报true。让我更加困惑的是，失败消息显示actual.userId不是null，而是等于预期的 id！

Hibernate 或 JUnit 的什么怪癖导致实际的 User 对象在失败后出现？

4

1 回答 1

1

由于一个关于在不获取整个对象的情况下获取 ids 的问题，我和一些朋友找到了解决方案。由于该对象是一个代理，直接引用该字段userid会equals产生一个空值。但是，对用户 ID 使用 getter 方法会导致从数据库中获取实际值。因此，该equals方法应如下所示：

@Override
public boolean equals(Object object){
    if (!(object instanceof User)) {
        return false;
    }
    User other = (User) object;
    if ((this.getUserId() == null && other.getUserId() != null) || 
        (this.getUserId() != null && 
        !this.getUserId().equals(other.getUserId()))) {
        return false;
    }
    return true;
}

现在断言将成立。

于 2012-04-17T16:28:23.457 回答