如何使用Hibernate在集合内部持久化实体？

Question

我正在尝试使用Hibernate ORM将实体保留在数据库中。 我的entity class

@Entity
@Table(name = "company")
public class Company implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;

    @Column
    private String name;

    @OneToMany(mappedBy = "company")
    @LazyCollection(LazyCollectionOption.FALSE)
    private Collection<Employee> employees;

资料库

@Repository
@Transactional(propagation = Propagation.REQUIRED)
public class HibernateCompanyRepository implements CompanyRepository {

    @Autowired
    HibernateTemplate template;

    @Override
    public Company getCompany(int id) {
        return template.get(Company.class, id);
    }

    @Override
    public Collection<Company> getCompanies() {
        return template.loadAll(Company.class);
    }

    @Override
    public void addCompany(Company employee) {
        template.save(employee);
    }

    @Override
    public void deleteCompany(int id) {
        template.delete(template.get(Company.class, id));
    }

    @Override
    public void updateCompany(Company company) {
        template.update(company);
    }
}

这是我的控制器

@Controller
@RequestMapping("/company")
public class CompanyController {

    @Autowired
    CompanyRepository companyRepository;

    @RequestMapping(value = "/{id}",
                    method = RequestMethod.GET,
                    produces = "application/json")
    @ResponseBody public Company getCompany(@PathVariable("id") Integer id) {
        return companyRepository.getCompany(id);
    }

    @RequestMapping(method = RequestMethod.PUT,
                    consumes = "application/json",
                    headers = "content-type=application/json")
    public String updateCompany(@RequestBody Company company) {
        companyRepository.updateCompany(company);
        return "redirect:/company/" + company.getId();
    }

    // another methods ommited    
}

旧的JSON

{
  "name" : "IBM",
  "employees" : [
    {
      "name" : "John",
      "id" : 2
    },
    {
      "name" : "Bill",
      "id" : 4
    }
  ],
  "id" : 2
}

更新了JSON（清单已删除）

{
  "name" : "IBM",
  "employees" : [
    {
      "name" : "John",
      "id" : 2
    }
  ],
  "id" : 2
}

我在updateCompany()方法中收到一个Employee实体。 Entity已成功更新。 它更改了Employee的集合（例如，我删除了一名雇员）。 但是Hibernate无法持久存储此更新的实体。 当我尝试检索它时，我看不到任何变化。 有什么建议如何解决吗？

UPD：

我正在尝试先更新已删除的员工

@Override
public void updateCompany(Company company) {
    Company oldCompany = getCompany(company.getId());
    for (Employee employee : oldCompany.getEmployees()) {
        if (!company.getEmployees().contains(employee)) {
            employee.setCompany(null);
            template.update(employee);
        }
    }
    template.update(company);
}

并获得例外

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.springframework.dao.DuplicateKeyException: a different object with the same identifier value was already associated with the session: [eu.flavio.restful.entity.Company#2]; nested exception is org.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: [eu.flavio..restful.entity.Company#2]

Answer 1

Hibernate重要的是双向关联的所有者。 所有者端是不具有mappedBy属性的端。 这就是寻找实体之间是否存在不存在关联的地方。

因此，此处的所有者是Employee.company 。 Company.employees是相反的一面。 如果您希望Bill不再是IBM的一部分，则必须确保Bill的公司设置为null。