[英]Hibernate Criterion in OneToMany relationship
我試圖找出如何使用hibernate標准來獲取一個特定的子元素集,當我檢索父元素。 我創建了以下示例實體:
家長班
@Entity
public class Parent {
@Id
@Column(name="PARENT_ID")
private long parentId;
@Column(name="NAME")
private String name;
@OneToMany(mappedBy="parent")
private Set<Child> children
}
兒童班
@Entity
public class Child {
@Id
@Column(name="CHILD_ID")
private long childId
@ManyToOne
@JoinColumn(name="PARENT_ID")
private Parent parent;
@ManyToOne
@JoinColumn(name="GENDER_ID")
private Gender gender;
}
性別等級
@Entity
public class Gender {
@Id
@Column(name="GENDER_ID")
private long genderId;
@Column(name="GENDER_IND")
private String genderInd;
}
休眠標准
getSession()
.createCriteria(Parent.class)
.createAlias("children", "c")
.createAlias("c.gender", "g")
.add(Restrictions.eq("g.genderInd", "M"))
.list()
這個標准給了我一份父母的名單,這些父母有一個男性(“M”)孩子,並且每個父母都會返回所有孩子。 我怎樣才能獲得一個父母的名單,這些父母有一個男孩,只有在Parent.children中設置了男孩?
我搜索了幾天的解決方案,我有同樣的問題,我有一個帶有一系列traductions的對象,我想用唯一的當前語言查詢一個對象。
我找到了這個解決方案: https : //docs.jboss.org/hibernate/orm/3.6/reference/en-US/html/filters.html
為我工作,這里有一個解決方案:
@Entity
public class Parent {
@Id
@Column(name="PARENT_ID")
private long parentId;
@Column(name="NAME")
private String name;
@OneToMany(mappedBy="parent")
@Filter(name="gender", condition="gender.genderInd=:gender")
private Set<Child> children
}
@Entity
@FilterDef(name="genderFilter", parameters=@ParamDef( name="gender", type="string" ) )
public class Child {
@Id
@Column(name="CHILD_ID")
private long childId
@ManyToOne
@JoinColumn(name="PARENT_ID")
private Parent parent;
@ManyToOne
@JoinColumn(name="GENDER_ID")
private Gender gender;
}
在進行查詢之前:
Session session = sessionFactory.getCurrentSession();
session.enableFilter("genderFilter").setParameter("gender", "M");
Criteria cr = getSession()
.createCriteria(Parent.class)
.createAlias("children", "c")
.createAlias("c.gender", "g");
Criterion Malechild = Restrictions.eq("g.genderInd", "M");
Criterion NFemaleChild = Restrictions.ne("g.genderInd", "F");
LogicalExpression andExp = Restrictions.and(Malechild, NFemaleChild);
cr.add(andExp);
List results = cr.list();
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