title: parse complex Gson , nested inner class was not parsed
body: <p>I use gson.fromJson(jsonStr, JVisitorResponse) method to parse the JSON reponse string, <b>all were parsed except the inner class JUserUrls</b>, there must be something wrong, my wrong usage of Gson caused this, please help me.</p>
  
  <p>My outer reponse class defined below:</p>
  
  <pre><code>public class JVisitorResponse extends BaseResponsePojo {
  
      public int count;
  
      @SerializedName("visitor_list")
      public ArrayList&lt;JVisitor&gt; visitorList;
  
      public JVisitorResponse() {
      }   
  }
  </code></pre>
  
  <p>JVIsitor class defined below:</p>
  
  <pre><code>public class JVisitor {
  
      @SerializedName("user_id")
      public long uid;
      @SerializedName("user_name")
      public String userName;
      @SerializedName("user_urls")
      public JUserUrls userHeadUrls;
  }
  </code></pre>
  
  <p>JUserUrls class defiend below:</p>
  
  <pre><code>public class JUserUrls {
      @SerializedName("main_url")
      public String mainUrl;
  }
  </code></pre>
  
  <p>my JSON response was </p>
  
  <pre><code>{
      count:30,
      visitor_list:[
          {
              user_id:333333,
              user_name:"jason lee",
              user_urls:{
                  main_url:"http://xxxxxxxxxx.jpg"
              }
          },
          ...
      ]
   }
  </code></pre>