我正在搜索一种方法,使用带有元模型的jpa条件查询API选择父实体的所有子实体。
表格族
@Entity
@Table(name = "FAMILIES")
public class Family {
private Long familyId;
private String familyName;
private List<FamilyMember> familyMembers;
@Id
@Column(name="ID_FAMILY")
@GeneratedValue(strategy = Generator.AUTO)
public Long getFamilyId() { return familyId;}
public void setFamilyId(Long fId) { familyId = fId;}
@Column(name = "family_name")
public String getFamilyName() { return familyName;}
public void setFamilyName(String fN) { familyName = fN;}
@OneToMany(mappedBy = "family")
@JoinColumn(name = "id_family")
public List<FamilyMember> getFamilyMembers() { return familyMembers;}
public void setFamilyMembers(List<FamilyMember> fM) { familyMembers = fM}
}
表family\u成员
@Entity
@Table(name = "family_members")
public class FamilyMember {
private Long familyMemberId;
private Family family;
private String name;
private String role;
@Id
@Column(name="ID_FAMILY_MEMBER")
@GeneratedValue(strategy = Generator.AUTO)
public Long getFamilyMemberId() { return familyMemberId;}
public void setFamilyMemberId(Long fMId) { familyMemberId = fMId;}
@ManyToOne
@JoinColumn(name = "id_family")
public String getFamily() { return family;}
public void setFamily(Family f) { family = f;}
@Column(name = "name")
public String getFamilyMemberName() { return name;}
public void setFamilyMemberName(String fMN) { name = fMN;}
@Column(name = "role")
public String getFamilyMemberRole() { return role;}
public void setFamilyMemberRole(String fMR) { role = fMR;}
}
现在,我想在选择族时选择族的所有子实体,而不是使用更慢的方法获取所有族的列表,循环列表并填充族成员列表。
为了通过普通SQL实现此结果,我编写了如下查询:
SELECT f.family_name, fM.name, fM.role FROM families AS f LEFT JOIN family_members AS fM ON fM.id_family = f.id_family;
现在我的问题是,如何将此本机查询转换为criteria API查询。
实际上,使用criteria API,我尝试了以下方法:
CriteriaBuilder cB = eM.getCriteriaBuilder();
CriteriaQuery<Family> fCQ = cB.createQuery(Family.class);
Root<Family> fromFamily = fCQ.from(Family.class);
ListJoin<Family, FamilyMember> members = fromFamily.join(Family_.familyMembers);
TypedQuery<Family> fTQ = eM.createQuery(fCQ);
但是,当我调用getResultList()时,我得到一个只包含族实体的列表,其中族表的行数乘以family\u memebers的行数。