同一实体上的JPA OneToOne和OneToMany

问题描述：

可能重复:
两个实体之间的JPA OneToOne和ManyToMany

我一直在寻找无济于事的解决方案.我的问题是我有两个实体雇员"和部门"许多员工属于一个部门一个部门由一名雇员领导.随时都会出现错误，同时介绍@OneToOne和@OneToMany.这是代码

I've searched for a solution to no avail. My question is I have two entities "Employee" and "Department" Many Employees belongs to One Department And One Department is headed by One Employee. Am getting errors anytime introduce both the @OneToOne and @OneToMany. This is the code

public class Department {
@Required
public String deptName; 

@OneToMany(mappedBy="dept")
public List<Employee> employees = new ArrayList<Employee>();

@OneToOne
public Employee deptHead = new Employee();

    .....   

}

public class Employee{
@Required
public String surname;

@Required
public String othernames;   

@OneToOne(mappedBy="depthead")
public Department headedBy = new Department();

@ManyToOne
public Department dept = new Department();

... 
}

是否可以同时具有注释和工作?

Is it possible to have both aNnotation and work at the same time?

答

应该是.

在创建或要求JPA创建 Employee 的实例时， Employee 会尝试实例化 Department ，将 Employee ...实例化为无穷大.

When you create, or ask JPA to create, an instance of Employee, the Employee attempts to instantiate a Department, which instantiates an Employee ..., to infinity.

从类定义中删除 = new Employee()和= new Department()表达式；使用适当的setter方法.

Remove the = new Employee() and = new Department() expressions from the class definition; use appropriate setter methods.

验证是否在 Department 表上定义了定义一对一关系的SQL列；特别是 Department 表具有一个引用 Employee 的外键.这样做的基础是，应在没有没有SQL外键的JPA实体上定义 @OneToOne(mappedBy ="...")引用执行的实体.

Verify that the SQL column defining the one-to-one relationship is defined on the Department table; specifically the Department table has a foreign-key referencing an Employee. The basis for this is that the @OneToOne(mappedBy="...") should be defined on the JPA Entity that does not have an SQL foreign key, referencing the entity that does.

此外，两者之间存在问题

That aside, there is an issue between

@OneToOne(mappedBy="depthead")
public Department headedBy = new Department();

以及部门上的相应字段:

@OneToOne
public Employee deptHead = new Employee();

depthead 和 deptHead 之间的情况不匹配.

There's a mismatch in case between depthead and deptHead, respectively.

同一实体上的JPA OneToOne和OneToMany

相关推荐