title: Parsing JSON with Jackson return null
body: <p>I'm training my self on java using API. The subject of my exercise is to ask google books API in order to take some infos about books. I use Jersey as a client and Jackson to parse the JSON.</p>
  
  <p>My problem is that when i run the <code>JerseyVolumeGet()</code> , the response is this one : </p>
  
  <pre><code>Volume{title='null', numberOfPages=null, author='null'}
  </code></pre>
  
  <p>Why ? Where is my mistake ? I suspect i get wrong when parsing the JSON but don't see where exactly..</p>
  
  <p>Here my getClass ( the search url is barcoded , it's not a problem for me)</p>
  
  <pre><code>public class JerseyVolumeGet {
      public static void main(String[] args) {
          try {
  
              Client client = Client.create();
  
              WebResource webResource = client
                      .resource("https://www.googleapis.com/books/v1/volumes?q=1984");
  
              ClientResponse response = webResource.accept("application/json")
                      .get(ClientResponse.class);
  
              if (response.getStatus() != 200) {
                  throw new RuntimeException("Noob you Failed : HTTP error code : "
                          + response.getStatus());
              }
  
              String output = response.getEntity(String.class);
  
              // read from file, convert it to user class
              ObjectMapper mapper = new ObjectMapper();
              Volume volume = mapper.readValue(output, Volume.class);
  
  
              // display to console
              System.out.println(volume);
  
  
          } catch (Exception e) {
  
              e.printStackTrace();
  
          }
  
      }
  
  }
  </code></pre>
  
  <p>Here the JSON result of my query :
  </p>
  
  <pre><code>{
   "kind": "books#volumes",
   "totalItems": 641,
   "items": [
    {
     "kind": "books#volume",
     "id": "RY8yQWeDVFYC",
     "etag": "Lf0P50PVz9c",
     "selfLink": "https://www.googleapis.com/books/v1/volumes/RY8yQWeDVFYC",
     "volumeInfo": {
      "title": "(1984).",
      "subtitle": "",
      "authors": [
       "Guy Serbat",
       "Jean Taillardat",
       "Gilbert Lazard"
      ],
      "publisher": "Peeters Publishers",
      "publishedDate": "1984-01-01",
      "description": "(Peeters 1984)",
      "industryIdentifiers": [
       {
        "type": "ISBN_10",
        "identifier": "2904685030"
       },
       {
        "type": "ISBN_13",
        "identifier": "9782904685033"
       }
      ],
      "readingModes": {
       "text": false,
       "image": true
      },
      "pageCount": 280,
      "printType": "BOOK",
      "categories": [
       "Language Arts &amp; Disciplines"
      ],
      "contentVersion": "1.1.1.0.preview.1",
      "imageLinks": {
       "smallThumbnail": "http://bks9.books.google.fr/books?id=RY8yQWeDVFYC&amp;printsec=frontcover&amp;img=1&amp;zoom=5&amp;edge=curl&amp;source=gbs_api",
       "thumbnail": "http://bks9.books.google.fr/books?id=RY8yQWeDVFYC&amp;printsec=frontcover&amp;img=1&amp;zoom=1&amp;edge=curl&amp;source=gbs_api"
      },
      "language": "fr",
      "previewLink": "http://books.google.fr/books?id=RY8yQWeDVFYC&amp;printsec=frontcover&amp;dq=1984&amp;hl=&amp;cd=1&amp;source=gbs_api",
      "infoLink": "http://books.google.fr/books?id=RY8yQWeDVFYC&amp;dq=1984&amp;hl=&amp;source=gbs_api",
      "canonicalVolumeLink": "http://books.google.fr/books/about/1984.html?hl=&amp;id=RY8yQWeDVFYC"
     },
     "saleInfo": {
      "country": "FR",
      "saleability": "NOT_FOR_SALE",
      "isEbook": false
     },
     "accessInfo": {
      "country": "FR",
      "viewability": "PARTIAL",
      "embeddable": true,
      "publicDomain": false,
      "textToSpeechPermission": "ALLOWED",
      "epub": {
       "isAvailable": false
      },
      "pdf": {
       "isAvailable": false
      },
      "webReaderLink": "http://books.google.fr/books/reader?id=RY8yQWeDVFYC&amp;hl=&amp;printsec=frontcover&amp;output=reader&amp;source=gbs_api",
      "accessViewStatus": "SAMPLE",
      "quoteSharingAllowed": false
     },
     "searchInfo": {
      "textSnippet": "(Peeters 1984)"
     }
    },
  more items...
  }
  </code></pre>
  
  <p></p>
  
  <p>Then , i've a <code>Volume.class</code> like that :</p>
  
  <pre><code>@JsonIgnoreProperties(ignoreUnknown=true)
  public class Volume {
      @JsonProperty("title")
      String title;
      @JsonProperty("pageCount")
      Integer pageCount;
      @JsonProperty("authors")
      String authors;
  
  getters , setters and toString..
  </code></pre>