[英]Can I use only Entity's id instead of fetching an entity from DB when there is a relationship in an Entity?
[英]How can I retrieve only an attribute instead of the Entity from a relationship?
我正在Netbeans中從事Maven Web應用程序項目,我有以下課程:
@Entity
@Table(name = "departments")
public class Department{
@Id
private Integer departmentId;
@Column(name = "department_name")
private String departmentName;
}
和:
@Entity
@Table(name = "employees")
public class Employee {
@Id
private Integer employeetId;
@Column(name = "employee_name")
private String employeeName;
@JoinColumn(name = "department_id", referencedColumnName =
"department_id")
@ManyToOne(optional = false)
private Departments department;
}
我的休息API返回此:
{
employeeId:1,
employeeName:"Jhon",
department: { departmentId:1, departmentName:"IT"}
}
我想要的輸出是:
{
employeeId:1,
employeeName:"Jhon",
department: "IT"
}
我嘗試返回DTO,但得到一個空的json:
@GET
@Produces(MediaType.APPLICATION_JSON)
public List<EmployeeDto> findAllEmployees() {
CriteriaQuery cq = entityManager.getCriteriaBuilder().createQuery(Employee.class);
cq.select(cq.from(Employee.class));
List<Employee> employees = entityManager.createQuery(cq).getResultList();
List<EmployeeDto> employeesDto = new ArrayList<>();
for (Employee employee : employees) {
EmployeeDto employeeDto = new EmployeeDto();
employeeDto.employeeId = employee.getEmployeedId();
employeeDto.department = employee.getDepartment().getDepartmentName();
employeesDto.add(employeeDto);
}
return employeesDto;
DTO:
Class EmployeeDto{Integer employeeId; String employeeName; String department}
使用命名查詢
@Entity
@Table(name="employees")
@NamedQueries({
@NamedQuery(
name = "getDesiredUser",
query = "SELECT e.employeeId, e.employeeName, d.departmentName FROM employees AS e INNER JOIN departments as d ON e.department_id = d.departmentId"),
})
public class Employee {
@Id
..
}
您可以在NamedQueries上找到更多信息:
這是因為我得到了一個空的json:我的Dto類沒有公共的獲取器和設置器。 解決方案是公開Dto字段或添加公共獲取者/設置者。
Class EmployeeDto{
public Integer employeeId;
public String employeeName;
public String department;
}
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