title: XmlElement required = true for Integer doesn't work
body: <p>I use jax-rs service. I have two fields in my class annotated with @XmlElement(required = true), one for Boolean, another for Integer. but if I send xml tags without value, for boolean I receive null, but for Integer I receive 0</p>
  
  <pre><code>@XmlElement(required = true)
  private Integer intValue;
  
  @XmlElement(required = true)
  private Boolean booleanValue;
  </code></pre>
  
  <p>why I'm not receive null in Integer?</p>