title: Can't save entity Embeddable Id
body: <p>I have <code>EcranChamp</code> entity</p>
  
  <pre><code>@Entity
  @IdClass(EcranChampId.class)
  public class EcranChamp {
  
  @Id
  @ManyToOne(fetch = FetchType.LAZY)
  @JoinColumn(name = "ecran")
  Ecran ecran;
  
  
  @Id
  @ManyToOne(fetch = FetchType.LAZY)
  @JoinColumn(name = "champ")
  Champ champ;
  
  ...
  </code></pre>
  
  <p>And <code>EcranChampId</code></p>
  
  <pre><code>@Embeddable
  public class EcranChampId implements Serializable  {    
  private Champ champ;  
  private Ecran ecran;
  ...
  </code></pre>
  
  <p>Every time i am trying to save an <code>EcranChamp</code> element i have this following error </p>
  
  <blockquote>
    <p>2018-09-25 12:15:42.889  WARN 14216 --- [nio-8092-exec-8] .w.s.m.s.DefaultHandlerExceptionResolver : Failed to convert request element: org.springframework.beans.ConversionNotSupportedException: Failed to convert property value of type 'java.lang.Long' to required type 'com.kepler.portailclient.domain.model.Ecran' for property 'ecran'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.lang.Long' to required type 'com.kepler.portailclient.domain.model.Ecran' for property 'ecran': no matching editors or conversion strategy found
    2018-09-25 12:15:42.889  WARN 14216 --- [nio-8092-exec-8] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved exception caused by Handler execution: org.springframework.beans.ConversionNotSupportedException: Failed to convert property value of type 'java.lang.Long' to required type 'com.kepler.portailclient.domain.model.Ecran' for property 'ecran'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.lang.Long' to required type 'com.kepler.portailclient.domain.model.Ecran' for property 'ecran': no matching editors or conversion strategy found</p>
  </blockquote>