java - 多对一关系的 API 请求

Question

我正在尝试构建一个具有 ManyToOne 关系的 API。它与员工和部门实体有关。这就是我所拥有的:

@Entity
@Table
public class Employee {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue
    private Long Id;
    private String name;
    @ManyToOne(fetch=FetchType.LAZY)
    private Department department;
    //SETTERS AND GETTERS, TWO CONSTRUCTORS 
}

院系类(class)

 @Entity
@Table
public class Department {

    @Id
    @GeneratedValue
    private Long Id;
    private String name;
    //SETTERS AND GETTERS, TWO CONSTRUCTORS 
}

员工 Controller

@RestController
public class EmployeeController {

    @Autowired
    EmployeeService employeeService;

    @PostMapping("/employee")
    public Employee create (@RequestBody Employee employee){

          return employeeService.create(employee);
    }
}

部门主管

 @RestController
 public class DepartmentController {

     @Autowired
     private DepartmentService departmentService;

     @PostMapping("/departments")
     public Department create(@RequestBody Department department) {
       return departmentService.create(department);
   }
}

我需要添加一个部门，然后添加属于该部门的员工。

这是向部门发送的 POST 请求，它有效。

{
    "id": 2,
    "name": "Depto"             
 }

我需要将该部门添加到员工

 {
     "id": 2,
     "name": "Employee",
     "department": 2
 }

这是我得到的错误:

 .HttpMessageNotReadableException: Could not read document: Cannot construct instance of 'mypackage.Department' (although at least one Creator exists): no int/Int-argument constructor/factory method to deserialize from Number value (2)

Answer 1

Employee 类中的 department 字段是 Department 的实例，而不是整数。所以你发布的 JSON 是错误的。事实上，使用与通过 REST 调用发送的内容相同的类来持久保存在数据库中是不好的架构实践。

如果将它们分开(使 REST 对象成为 DTO)，那么您可以接收 id (2)，查找 id 2 的部门，然后将其放入新的 Employee 对象中，然后将其保存到数据库。

编辑:您可以创建一个 EmployeeDTO 类:

public class EmployeeDTO {
    private Long id;
    private String name;
    private Long departmentId;

    ...  // getters
}

你的 Controller 可能有一个像这样的端点:

@PostMapping("/employee")
public Employee create (@RequestBody EmployeeDTO employeeDTO){

    Department department = departmentService.get(employeeDTO.getDepartmentId());

    Employee employee = new Employee();
    employee.setId(employeeDTO.getId());
    employee.setName(employeeDTO.getName());
    employee.setDepartment(department);

    return employeeService.create(employee);
}