I have two tables... For example - Company and Employee (let's keep this real simple)
我有两张桌子......例如 - 公司和员工(让我们保持这简单)
Company( id, name );
Employee( id, company_id );
Employee.company_id is a foreign key.
Employee.company_id是外键。
My entity model looks like this...
我的实体模型看起来像这样......
Employee
@ManyToOne(cascade = CascadeType.PERSIST)
@JoinColumn(name = "company_id")
Company company;
Company
@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
@JoinColumn(name = "company_id")
List<Employee> employeeList = new ArrayList<Employee>();
So, yeah I want a list of employees for a company.
所以,是的,我想要一份公司员工名单。
When I do the following...
当我做以下事情......
Employee e = new Employee();
e.setCompany(c); //c is an Company that is already in the database.
DAO.insertEmployee(e); //this works fine!
If I then get my Company object it's list is empty!
如果我然后得到我的公司对象它的列表是空的!
Ive tried endless different ways from the Hibernate documentation!
我尝试过Hibernate文档中不同的方法!
Obviously not tried the correct one yet!
显然没有尝试过正确的!
I just want the list to be populated for me or find out a sensible alternative.
我只是希望为我填充列表或找到一个明智的选择。
Help would be greatly appreciated, thanks!
非常感谢帮助,谢谢!
2 个解决方案
#1
5
You need to make the relationship bidirectional. Yours is two unidirectional ones. Add mappedBy = "company" to employeeList. This tells hibernate the employee list is simply the reverse of the ref from Employee to Company
您需要使关系双向。你的是两个单向的。将mappedBy =“company”添加到employeeList。这告诉hibernate员工列表只是从Employee到Company的ref的反向
@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, mappedBy = "company")
List<Employee> employeeList = new ArrayList<Employee>();
#2
0
I dont think you should do List<Employee> employeeList = new ArrayList<Employee>(); This should be done when you have defined the side which has the list as the owning side which in your case is the Employee and not the Company. I think each time you load the Company instance, you are being supplied with a new instance of employeeList, not sure though. But surely, there is no need to instantiate the new ArrayList each time.
我不认为你应该做List
#1
5
You need to make the relationship bidirectional. Yours is two unidirectional ones. Add mappedBy = "company" to employeeList. This tells hibernate the employee list is simply the reverse of the ref from Employee to Company
您需要使关系双向。你的是两个单向的。将mappedBy =“company”添加到employeeList。这告诉hibernate员工列表只是从Employee到Company的ref的反向
@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, mappedBy = "company")
List<Employee> employeeList = new ArrayList<Employee>();
#2
0
I dont think you should do List<Employee> employeeList = new ArrayList<Employee>(); This should be done when you have defined the side which has the list as the owning side which in your case is the Employee and not the Company. I think each time you load the Company instance, you are being supplied with a new instance of employeeList, not sure though. But surely, there is no need to instantiate the new ArrayList each time.
我不认为你应该做List