title: GStringImpl cannot be cast to java.lang.String
body: <p>I got the error below using Grails and Spring Security. Has anyone else had a problem like this? If so, what was your fix?</p>
  
  <pre><code>Error |
  Exception in thread "Thread-15" 
  Error |
  java.lang.ClassCastException: org.codehaus.groovy.runtime.GStringImpl cannot be cast to java.lang.String
  Error |
      at org.codehaus.groovy.grails.project.compiler.GrailsProjectWatcher.run(GrailsProjectWatcher.java:114)
  </code></pre>
  
  <p>And </p>
  
  <pre><code>java.lang.IllegalArgumentException: Failed to evaluate expression 'User_name'
  </code></pre>