title: Jackson: Deserialize map<String,Object> where keys have index into Custom nested Pojo
body: <p>I have a simple Map and I would like to deserialize it to a Pojo with some internal nested classes.</p>
  
  <p>Example for map: </p>
  
  <p><code>Map = ["total_errs"=20, "err_1_day"=3, "err_2_day"=1, ..., "err_30_day=5"]</code></p>
  
  <p>I would like to deserialize this into a nice Pojo as follow:</p>
  
  <pre><code>class CustomPojo {
     @JsonProperty("total_errs")
     private long totalErrors;
  
     private List&lt;ErrorByDay&gt; errByDays;
  
     static class ErrorByDay {
        private long age; // age is the key of each map entry
        private long count; // count is the value of each map entry
      }
  }
  </code></pre>
  
  <p>Calling code:</p>
  
  <p><code>CustomPojo pojo = new ObjectMapper().convert(map, CustomPojo.class);</code></p>
  
  <p>Is there a nice way to solve this using annotations only? (I know I can write a custom Deserializer for that).</p>
  
  <p>Thank you!</p>