title: AttributeOverride set null value to unmapped field
body: <p>I have class </p>
  
  <pre><code>@Embeddable
  public class MyClass implements Serializable
  {
     private String field1;
     private String field2;
     private String field3;
  
  // getters, setters
  }
  </code></pre>
  
  <p>and I have mapped class</p>
  
  <pre><code>public class MappedClass implements Serializable
  {
     @Embedded
     @AttributeOverrides(
        {
          @AttributeOverride(name = "field1", column = @Column(name = "column1")),
          @AttributeOverride(name = "field2", column = @Column(name = "column2")),
          @AttributeOverride(name = "field3", column = @Column(name = "column3"))
        })
     private MyClass myClassField1;
  
     @Embedded
     @AttributeOverrides(
        {
          @AttributeOverride(name = "field1", column = @Column(name = "column1")),
          @AttributeOverride(name = "field2", column = @Column(name = "column2")),
        })
     private MyClass myClassField2;
  
  // setters, getters
  
  }
  </code></pre>
  
  <p>I want that 'filed3' in myClassField2 be 'null', becouse 'field3' hasn't DB mapping.
  What can I do? JPA search value for 'field3' in column 'field3' </p>
  
  <p>In Hibernate all passed normal!  </p>
  
  <pre><code>   &lt;component name="myClassField1" class="MappedClass"&gt;
             &lt;property name="field1" type="string" column="column1" /&gt;
             &lt;property name="field2" type="string" column="column2" /&gt;
             &lt;property name="field3" type="string" column="column3" /&gt;
     &lt;component/&gt;  
  
     &lt;component name="myClassField2" class="MappedClass"&gt;
             &lt;property name="field1" type="string" column="column1" /&gt;
             &lt;property name="field2" type="string" column="column2" /&gt;
     &lt;component/&gt;  
  </code></pre>
  
  <p>But I need this in JPA</p>