title: How to expose methods or similar alternative
body: <p>As a simple example I have a doctrine entity with the following fields</p>
  
  <pre><code>id
  name
  description
  </code></pre>
  
  <p>I am using <code>JMSSerializerBundle</code> and it is working well in most cases, however what if I wanted to have the serialized data (the Json) include something that is not mapped exactly to my entity.</p>
  
  <p>For example, what if I only wanted the first 50 characters of the description returned and I wanted to call that <code>short_description</code>.</p>
  
  <p>I tried to use the Exclusion Strategies with <code>@Expose</code> to expose a method, but this is not supported.</p>
  
  <p>I will need to do this kind of thing frequently and with many different entities, I was wondering if anyone could suggest a nice clean approach to this.</p>
  
  <p>I have read the entire documentation of <code>JMSSerializerBundle</code> and also looked for solutions on the internet, I can think up some solutions but the resulting code looks a bit dirty.</p>