我想扩展earlier post中提到的要求以支持删除。我们有两个数据模型对象-组织和部门共享一对多关系。通过以下映射,我可以从组织对象中读取部门列表。我尚未添加级联ALL属性来限制在创建组织时添加部门。
我应该如何修改@OneToMany批注(可能还有@ManyToOne)以限制部门的插入,但是级联删除操作,以便在删除组织对象时删除所有关联的部门?
@Entity
@Table(name="ORGANIZATIONS")
public class Organization{
@Id
@GeneratedValue
Private long id;
@Column(unique=true)
Private String name;
@OneToMany(mappedBy = "organization", fetch = FetchType.EAGER)
private List<Department> departments;
}
@Entity
@Table(name="DEPARTMENTS")
Public class Department{
@Id
@GeneratedValue
Private long id;
@Column(unique=true)
Private String name;
@ManyToOne(fetch = FetchType.EAGER)
private Organization organization;
}
删除组织的代码只是一行
organizationRepository.deleteById(orgId);
验证此情况的测试用例如下
@RunWith(SpringJUnit4ClassRunner.class)
@DataJpaTest
@Transactional
public class OrganizationRepositoryTests {
@Autowired
private OrganizationRepository organizationRepository;
@Autowired
private DepartmentRepository departmentRepository;
@Test
public void testDeleteOrganization() {
final organization organization = organizationRepository.findByName(organizationName).get(); //precondition
Department d1 = new Department();
d1.setName("d1");
d1.setorganization(organization);
Department d2 = new Department();
d2.setName("d2");
d2.setorganization(organization);
departmentRepository.save(d1);
departmentRepository.save(d2);
// assertEquals(2, organizationRepository.getOne(organization.getId()).getDepartments().size()); //this assert is failing. For some reason organizations does not have a list of departments
organizationRepository.deleteById(organization.getId());
assertFalse(organizationRepository.findByName(organizationName).isPresent());
assertEquals(0, departmentRepository.findAll().size()); //no departments should be found
}
}
答案 0 :(得分:1)
查看有关失败原因的代码注释:
@RunWith(SpringJUnit4ClassRunner.class)
@DataJpaTest
@Transactional
public class OrganizationRepositoryTests {
@Autowired
private OrganizationRepository organizationRepository;
@Autowired
private DepartmentRepository departmentRepository;
@PersistenceContext
private Entitymanager em;
@Test
public void testDeleteOrganization() {
Organization organization =
organizationRepository.findByName(organizationName).get();
Department d1 = new Department();
d1.setName("d1");
d1.setOrganization(organization);
Department d2 = new Department();
d2.setName("d2");
d2.setOrganization(organization);
departmentRepository.save(d1);
departmentRepository.save(d2);
// this fails because there is no trip to the database as Organization
// (the one loaded in the first line)
// already exists in the current entityManager - and you have not
// updated its list of departments.
// uncommenting the following line will trigger a reload and prove
// this to be the case: however it is not a fix for the issue.
// em.clear();
assertEquals(2,
organizationRepository.getOne(
organization.getId()).getDepartments().size());
//similary this will execute without error with the em.clear()
//statement uncommented
//however without that Hibernate knows nothing about the cascacding
//delete as there are no departments
//associated with organisation as you have not added them to the list.
organizationRepository.deleteById(organization.getId());
assertFalse(organizationRepository.findByName(organizationName).isPresent());
assertEquals(0, departmentRepository.findAll().size());
}
}
正确的解决方法是封装封装的添加/删除/设置操作并防止出现以下情况,从而确保正确维护内存模型: 直接访问收藏集。 例如
public class Department(){
public void setOrganisation(Organisation organisation){
this.organisation = organisation;
if(! organisation.getDepartments().contains(department)){
organisation.addDepartment(department);
}
}
}
public class Organisation(){
public List<Department> getDepartments(){
return Collections.unmodifiableList(departments);
}
public void addDepartment(Department departmenmt){
departments.add(department);
if(department.getOrganisation() != this){
department.setOrganisation(this);
}
}
}
答案 1 :(得分:0)
您可以尝试添加以限制级联,以仅从组织到部门删除操作:
@OneToMany(mappedBy = "organization", fetch = FetchType.EAGER, cascade = CascadeType.REMOVE, orphanRemoval = true)
private List<Department> departments;
请注意,如果部门部门具有从属/外键约束,则还需要将删除操作也级联到这些从属实体。
您可以阅读本指南,它很好地说明了级联操作: https://vladmihalcea.com/a-beginners-guide-to-jpa-and-hibernate-cascade-types/
答案 2 :(得分:0)
尝试此代码,
@OneToMany( fetch = FetchType.EAGER, cascade = CascadeType.ALL)
@JoinColumn(name = "organisation_id", referencedColumnName = "id")
private List<Department> departments;
@ManyToOne(fetch = FetchType.EAGER,ascade = CascadeType.REFRESH,mappedBy = "departments")
private Organization organization;
如有任何问题,请告知