如何仅从关系中检索属性而不是实体？

Question

我正在 Netbeans 中开发一个 Maven Web 应用程序项目，我有以下类：@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 返回这个：{    employeeId:1,     employeeName:"Jhon",    department: { departmentId:1, departmentName:"IT"}}我想要的输出是： {    employeeId:1,     employeeName:"Jhon",    department: "IT" }我尝试返回一个 DTO，但得到一个空的 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}

Answer 1

这是因为我得到了一个空的 json：我的 Dto 类没有公共 getter 和 setter。解决方案是公开 Dto 字段或添加公共 getter/setter。

Class EmployeeDto{

    public Integer employeeId; 

    public String employeeName; 

    public String department;

}