title: Spring MVC 3.2 and JSON ObjectMapper issue
body: <p>I have recently upgraded my Spring version to 3.2.0 from 3.1.2. I find that that JSON properties like wrap root element, prevent null values that are defined in ObjectMapper are not working anymore. </p>
  
  <p>Here is the code snippet </p>
  
  <pre><code>&lt;mvc:annotation-driven content-negotiation-manager="contentNegotiationManager" /&gt; 
      &lt;bean id="contentNegotiationManager" class="org.springframework.web.accept.ContentNegotiationManagerFactoryBean"&gt;
      &lt;property name="favorPathExtension" value="true" /&gt;
      &lt;property name="ignoreAcceptHeader" value="false" /&gt; 
      &lt;property name="mediaTypes" &gt;
          &lt;value&gt;
              json=application/json
              xml=application/xml
          &lt;/value&gt;
      &lt;/property&gt;
  &lt;/bean&gt;
  </code></pre>
  
  <p>and the JSON converter</p>
  
  <pre><code>&lt;bean class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter"&gt;
     &lt;property name="objectMapper" ref="customJacksonObjectMapper"/&gt;  
     &lt;property name="supportedMediaTypes" value="application/json"/&gt;
  &lt;/bean&gt;
  </code></pre>
  
  <p>Object mapper code</p>
  
  <pre><code>public class CustomJacksonObjectMapper extends ObjectMapper {
  
  @SuppressWarnings("deprecation")
  public CustomJacksonObjectMapper() {
      super();
      final AnnotationIntrospector introspector = new JaxbAnnotationIntrospector();
  
      this.configure(org.codehaus.jackson.map.DeserializationConfig.Feature.UNWRAP_ROOT_VALUE, true);
      this.configure(org.codehaus.jackson.map.SerializationConfig.Feature.WRAP_ROOT_VALUE, true);
  
      this.configure(org.codehaus.jackson.map.SerializationConfig.Feature.WRITE_NULL_PROPERTIES, false);
  
      this.setDeserializationConfig(this.getDeserializationConfig().withAnnotationIntrospector(introspector));
      this.setSerializationConfig(this.getSerializationConfig().withAnnotationIntrospector(introspector));
  
     }
  }
  </code></pre>
  
  <p>Jackson version</p>
  
  <pre><code>&lt;dependency&gt;
          &lt;groupId&gt;org.codehaus.jackson&lt;/groupId&gt;
          &lt;artifactId&gt;jackson-xc&lt;/artifactId&gt;
          &lt;version&gt;1.9.7&lt;/version&gt;
      &lt;/dependency&gt;
  </code></pre>
  
  <p>What could be the issue? Any pointers are appreciated.</p>