Hibernate：Criteria API：查询 CollectionOfElements 中不包含指定元素的实体？
假设我有以下两门课程；用户和位置。我想创建一个 DetachedCriteria 来查询用户表，并返回没有名称为“xyz”的位置的所有用户。
@Entity
public class User {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
Long id;
@CollectionOfElements
Set<Location> locations;
}
@Entity
public class Location{
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
Long id;
@Column
String name;
}
以下代码将返回设置了名称“xyz”位置的所有用户：
DetachedCriteria dc = DetachedCriteria.forClass(User.class);
dc.createCriteria("locations")
dc.add(Restrictions.eq("name", "xyz"));
如果我更改为 Restrictions.ne()，则不起作用，因为它只会返回实际设置了位置的用户。此外，如果为某个用户设置了一堆位置，它会一遍又一遍地重复该用户。
有什么想法吗？
Let's say I have the following two classes; User and Location. I want to create a DetachedCriteria to query the user table, and return all users who do not have a location with the name "xyz".
@Entity
public class User {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
Long id;
@CollectionOfElements
Set<Location> locations;
}
@Entity
public class Location{
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
Long id;
@Column
String name;
}
The following code will return all users who DO have a location with name "xyz" set:
DetachedCriteria dc = DetachedCriteria.forClass(User.class);
dc.createCriteria("locations")
dc.add(Restrictions.eq("name", "xyz"));
If I change to Restrictions.ne(), that doesn't work, because it will only return users who actually have locations set. Also, if there are a bunch of locations set for a user, it will duplicate that user over and over.
Any ideas?
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使用原始帖子中所述的实体用户和位置：
1) 检查关联的位置是否为空。
2) 使用 LEFT_JOIN 和要在“ne”限制中使用的别名为位置创建关联条件。 LEFT_JOIN 是必需的，因此即使位置关系为空，我们仍然可以获得用户记录。
3) 将析取添加到原始用户条件。
Using the entities User and Location as described in your original post:
1) Check if the associated locations is empty.
2) Create an associated criteria for locations using a LEFT_JOIN and an alias to be used in the "ne" restriction. The LEFT_JOIN is required so we still get User records back even if the locations relationship is empty.
3) Add the disjunction to the the original User criteria.
您可能需要使用
Restrictions.and()、Restrictions.not()、Restrictions.or()和 < code>Restrictions.in() 让你的逆逻辑正常工作。检查 http://docs.jboss.org/ hibernate/core/3.5/api/org/hibernate/criterion/Restrictions.html - 绝对可以做到！为了确保您最多只获得一个
User，请使用Distinct投影（http://docs.jboss.org/hibernate/core/3.5/api/org /hibernate/criterion/Distinct.html) 通过Projections.distinct()工厂方法（http://docs.jboss.org/hibernate/core/3.5/api/org/hibernate/criterion/Projections.html）-即：类似的东西应该可以满足您的需要。
You'll probably need to use some combination of
Restrictions.and(),Restrictions.not(),Restrictions.or()andRestrictions.in()to get your inverse-logic to work right. Check http://docs.jboss.org/hibernate/core/3.5/api/org/hibernate/criterion/Restrictions.html - it can definitely be done!To ensure you only get at-most-one
User, use aDistinctprojection (http://docs.jboss.org/hibernate/core/3.5/api/org/hibernate/criterion/Distinct.html) via theProjections.distinct()factory method (http://docs.jboss.org/hibernate/core/3.5/api/org/hibernate/criterion/Projections.html)- i.e.:Something like that should do what you need.