Spring REST Controller returns JSON with empty data
<p>I have a simple Spring Boot web application. I'm trying to receive some data from server. The Controller returns a collection, but the browser receives empty JSON - the number of curly brackets is equals to the number of objects from server, but its content is empty.</p>

<pre><code>@RestController
public class EmployeeController {

@Autowired
private EmployeeManagerImpl employeeManagerImpl;

    @RequestMapping(path="/employees", method = RequestMethod.GET)
    public Iterable&lt;Employee&gt; getAllEmployees() {
        Iterable&lt;Employee&gt; employeesIterable = employeeManagerImpl.getAllEmployees();
        return employeesIterable;
    }
}
</code></pre>

<p>The method fires and a browser shows:</p>

<p><a href="https://i.stack.imgur.com/yYQxo.png" rel="noreferrer"><img src="https://i.stack.imgur.com/yYQxo.png" alt="enter image description here"></a></p>

<p>Nothing more in the console. Any ideas?</p>

<p>EDIT:
Employee.java</p>

<pre><code>@Entity
public 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(){

    }
}
</code></pre>