Google App Engine Utils
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Google App Engine Utilities

Some of the utilities helpful at Google App Engine (GAE)


One of the scenarios that people get uncomfortable with is the 3000 file limit on GAE, noting that the non-JSP files outside the /WEB-INF folder are counted twice on Java apps.

Based on a solution at GAE Issue 161, UnzipperServlet was born.

Enlisted below are some of its features:

  • Configure the zip file whose contents are to be served in web.xml as init-param
  • Allow support for a welcome file. TODO: Add support for welcome file list
  • Acknowledges the header If-Modified-Since and responds with 304 if need be
  • Acknowledges the header If-None-Match and responds with 304 if need be
  • Sends an ETag header. The checksum value is picked up from the md5 file.


  • For each file to be served by this servlet, create a md5 checksum file. Use md5sum utility to create the checksum. The file must be name original-file-name.md5
  • Compress all the static files in a zip file
  • Copy the zip file in a sub-folder in the WEB-INF/classes folder
  • Register the path, with a leading / in web.xml using the param-name of zipFile
  • Map the servlet to appropriate URL pattern
  • Enjoy!



  • Allow custom expiration setting, similar to that in appengine-web.xml using the * and ** patterns


Mail me at gaurav[dot]vaish[at]gmail[dot]com for any query / comments / critics. :)