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.

Usage:

• 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!

DEMO:

• The servlet is in live usage at http://2.latest.mastergaurav.appspot.com Using If-Modified-Since, If-None-Match and ETag headers
• The servlet is in live usage as http://1.latest.mastergaurav.appspot.com using If-Modified-Since only.

TODO:

• 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. :)