title: InvalidClassException error while deserializing session data
body: <p>Here is the calling code:</p>
  
  <pre><code>Object attribute = session.getAttribute(name, scope);
  </code></pre>
  
  <p>and this throws the following eror:</p>
  
  <pre><code>Could not deserialize session data.
  java.io.InvalidClassException: org.apache.commons.lang.time.FastDateFormat; local class  incompatible: stream classdesc serialVersionUID = 1, local class serialVersionUID = -7186497712641044641
  </code></pre>
  
  <p>The environment is Weblogic. The Web application is a spring portlet. I'm trying to understand how to fix this issue.</p>