I was trying to use free marker template language with struts.
I was using struts 2.2.3 version, FTL was working fine when i was not using any assignment directive to use struts tags lib.
But when i added the following line to my FTL file
i got the exception
When i googled about this error, i found out that this class used to exist in earlier versions of struts, but not in struts2.2.3
After wasting some hours, i found out the silly mistake i had made. I was using struts-tags.tld file from earlier version of struts. And that is why it was referencing the AutocompleterTag class.
So to solve this problem, just un-jar the struts2.2.3-core.jar file, and get the struts-tags.tld file from META-INF folder, and put it in your resources (WEB-INF/struts-tags.tld).