title: Jackson JSON Can not construct instance of "About" : deserialize issue
body: <p>I've make HttpsURLConnection to receive some information about my server.
  The result of response is : </p>
  
  <pre><code>{"about":{"title":"NiFi","version":"1.1.0","uri":"https://localhost:443/api/","contentViewerUrl":"/nifi-content-viewer/","timezone":"CET"}}
  </code></pre>
  
  <p>How is possible to extract all attributes and key/value ?</p>
  
  <h1>About.class file</h1>
  
  <pre><code>public class About {
  
  private List&lt;AboutObject&gt; about;
  public About()
  {
  //  this.about = about;
  }
  public List&lt;AboutObject&gt; getAbout() {
      return this.about;
  }
  public void setAbout(List&lt;AboutObject&gt; about) {
      this.about = about;
  }
  }
  </code></pre>
  
  <h1>AboutObject.class</h1>
  
  <pre><code>public class AboutObject {
  
  private String title;
  private String uri;
  private String contentViewerUrl;
  private String timezone;
  
  public String getTitle()
  {
      return this.title;
  }
  
  public void setTitle(String title)
  {
      this.title = title;
  }
  
  public String getUri()
  {
      return this.uri;
  }
  
  public void setUri(String uri)
  {
      this.uri = uri;
  }
  
  public String getContentViewerUrl()
  {
      return this.contentViewerUrl;
  }
  
  public void setContentViewerUrl(String contentViewerUrl)
  {
      this.contentViewerUrl = contentViewerUrl;
  }
  
  public String getTimeZone()
  {
      return this.timezone;
  }
  
  public void setTimeZone(String timezone)
  {
      this.timezone = timezone;
  }
  }
  </code></pre>
  
  <h1>Main.class</h1>
  
  <pre><code>HttpsURLConnection con = (HttpsURLConnection) obj.openConnection();
  
  // optional default is GET
  con.setRequestMethod("GET");
  
  //add request header
  con.setRequestProperty("User-Agent", USER_AGENT);
  
  int responseCode = con.getResponseCode();
  System.out.println("\nSending 'GET' request to URL : " + url);
  System.out.println("Response Code : " + responseCode);
  
  BufferedReader in = new BufferedReader(
          new InputStreamReader(con.getInputStream()));
  String inputLine;
  StringBuffer response = new StringBuffer();
  
  while ((inputLine = in.readLine()) != null) {
      response.append(inputLine);
  }
  in.close();
  
  //print result
  System.out.println(response.toString());
  
  System.out.println("Contenu de in = " + in.toString());
  
  ObjectMapper mapper = new ObjectMapper();
  //Staff objStaff = new Staff();
  
  System.out.println("Object to JSON in file");
  mapper.writeValue(new File("output/file.json"), response);
  System.out.println("Convert JSON string from file to Object");
  //String about = mapper.readValue(new File("output/file.json"), String.class);
  About about = mapper.readValue(new File("output/file.json"), About.class);
  </code></pre>
  
  <h1>Error</h1>
  
  <pre><code>Exception in thread "main" com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of About: no String-argument constructor/factory method to deserialize from String value ('{"about":{"title":"NiFi","version":"1.1.0","uri":"https://localhost:443/api/","contentViewerUrl":"/nifi-content-viewer/","timezone":"CET"}}') at [Source: output/file.json; line: 1, column: 1]
  </code></pre>
  
  <p>Thanks for you help</p>