如何从Google App Engine（Java）数据存储区中的子实体查询父实体？

我已经使用JPA注释在部门和雇员之间创建了一对多关系。实体是：

Department(Parent)
    String Id
    String Name
    List Employee(@OneToMany) 

Employee(Child)
    Key key
    String firstName
    String lastName
    String Address
    Department dept(@ManyToOne)

输入员工的名字时，我想显示该员工的详细信息（姓氏和地址），以及他所属的部门。我没有找到任何从子实体获取父信息的解决方案。有什么方法可以从其子实体获取有关父实体的信息吗？

我认为一种可能的解决方案是从child获取父ID，在另一个查询中获取Parent Detail。但我想在单个查询中提供有关员工的所有信息。这可能吗？

这是我的代码。

Department Entity:
    @Entity
    public class Department {

          @Id
          private String id;

          private String description;

          @OneToMany(mappedBy = "department", fetch=FetchType.EAGER, cascade = CascadeType.ALL)
          private List<Employee> employee = new ArrayList<Employee>();

          public String getId() {
              return id;
          }

          public void setId(String id) {
              this.id = id;
          }

          public String getDescription() {
            return description;
          }

          public void setDescription(String description) {
            this.description = description;
          }

          public List<Employee> getEmployee () {
                return employee ;
          }

          public void setEmployee (List<Employee > employee) {
                this.employee = employee ;
          }
    }

Employee Entity:
    @Entity
    public class Employee {
             @Id
             @GeneratedValue(strategy = GenerationType.IDENTITY)
             private Key key;

             private String firstName;
             private String lastName;
             private String Address;

             private String parent_Id;

             @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
             private Department department;

             public Key getKey() {
            return key;
             }

             public String getFirstName() {
                 return firstName;
             }

             public void setFirstName(String firstName) {
                 this.firstName = firstName;
             }

             public String getLastName() {
                 return lastName;
             }

             public void setLastName(String lastName) {
                 this.lastName = lastName;
             }

             public String getAddress() {
                return Address;
             }

             public void setAddress(String Address) {
                this.Address = Address;
             }
    }

Android代码在后台插入实体

Departmentendpoint.Builder builder1 = new                                          Departmentendpoint.Builder(AndroidHttp.newCompatibleTransport(), new JacksonFactory(), null);
Departmentendpoint dptendpoint = CloudEndpointUtils.updateBuilder(builder1).build();

    Department dpt = new Department();
    dpt.setDescription("Water Service"); 
    List<Employee> m = new ArrayList<Employee>();       
    Employee mgr2= new Employee();
    mgr2.setFirstName("Avinash"+i);
    mgr2.setLastName("Patel"+i);
    mgr2.setAddress("Vadodara");
    m.add(mgr2);    
    dpt.setEmployee(m);

    try {
        dptendpoint.insertDepartment(dpt).execute();
    } catch (IOException e) {
        e.printStackTrace();
    }