title: Jackson: Can not deserialize instance of Number out of START_OBJECT token
body: <p>My GWT service returns <code>LinkedList&lt;VisualData&gt;</code>. This is how <code>VisualData</code> looks:</p>
  
  <pre><code>import javax.xml.bind.annotation.XmlRootElement;
  import com.google.gwt.user.client.rpc.IsSerializable;
  
  @XmlRootElement
  public class VisualData implements IsSerializable {
      private Number value;
      private long timestamp;
  
      public VisualData() {
      }
  
      public VisualData(Number value, long timestamp) {
          this.value = value;
          this.timestamp = timestamp;
      }
  
      public long getTimestamp() {
          return timestamp;
      }
  
      public Number getValue() {
          return value;
      }
  
      public void setTimestamp(long timestamp) {
          this.timestamp = timestamp;
      }
  
      public void setValue(Number value) {
          this.value = value;
      }
  }
  </code></pre>
  
  <p>I get the following excepion connected with field <code>private Number value</code>.</p>
  
  <pre><code>SEVERE: The exception contained within MappableContainerException could not be mapped to a response, re-throwing to the HTTP container
  org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of java.lang.Number out of START_OBJECT token
  at [Source: org.apache.catalina.connector.CoyoteInputStream@a0eb51; line: 1, column: 29] (through reference chain: org.jage.charts.client.VisualData["value"])
  </code></pre>
  
  <p>When I change <code>private Number value</code> to <code>private Object value</code>, all getters and setters I get:</p>
  
  <pre><code>SEVERE: WebModule[/AgECharts]Exception while dispatching incoming RPC call
  com.google.gwt.user.client.rpc.SerializationException: Type 'org.jage.charts.client.VisualData' was not included in the set of types which can be serialized by this SerializationPolicy or its Class object could not be loaded. For security purposes, this type will not be serialized.: instance = Value:{@type=xs:int, $=6}, timestamp:1360240281439
  at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serialize(ServerSerializationStreamWriter.java:619)
  </code></pre>
  
  <p>This second case is quite clear, the <code>Object</code> class is not serializable. But why do I get <code>Can not deserialize instance of java.lang.Number out of START_OBJECT token</code>?</p>