java–Spring REST Controller返回带有空数据的JSON

我有一个简单的Spring Boot Web应用程序.我正在尝试从服务器接收一些数据. Controller返回一个集合,但浏览器接收空JSON – 大括号的数量等于来自服务器的对象数,但其内容为空.

@RestControllerpublic class EmployeeController {@autowiredprivate EmployeeManagerImpl employeeManagerImpl;    @RequestMapPing(path="/employees",method = RequestMethod.GET)    public Iterable

该方法触发,浏览器显示：

在控制台中没有更多.有任何想法吗？

编辑：
Employee.java

@Entitypublic class Employee implements Serializable{    private static final long serialVersionUID = -1723798766434132067L;    @ID    @Getter @Setter     @GeneratedValue    private Long ID;    @Getter @Setter    @Column(name = "first_name")    private String firstname;    @Getter @Setter    @Column(name = "last_name")    private String lastname;    @Getter @Setter    private BigDecimal salary;    public Employee(){    }}

@Entity@Getter@Setter@Builder@NoArgsConstructor@AllArgsConstructor    public class Employee implements Serializable {}