caching : Java Glossary

caching

Caching is a general term of keeping a small subset of a larger set handy for rapid access. SQL databases keep the most popular parts of the disk-based database in RAM (Random Access Memory). DNS lookup servers keep locally copies of the names it uses most frequently. Operating systems keep copies of the most commonly used parts of the hard disk in a RAM cache.

Starting withJava version 1.3, the Java Plugin offers Applet caching. This means Applets need be downloaded only when new versions have been uploaded to the server. Otherwise they are executed from a local cache. There are special plug-in commands to control which Applets are sticky and which are downloaded fresh each time.

To speed things up even further, so that last modified dates and jar sizes don’t need to be checked from the server, you can put jar version numbers in your <PARAM NAME="cache_version" tags. The cacher compares these with the version numbers in its cache to see if it needs to refresh the jar. The jars themselves have no such embedded version numbers.

To clear the in-RAM ClassLoader Applet cache in Internet Explorer, click Tools ⇒ Java Console ⇒ x .

To clear the in-RAM ClassLoader Applet cache in Opera, click Tools ⇒ Advanced ⇒ Java Console ⇒ x .

You can configure the cache size in a browser. Don’t be crazy generous. If you choose something like 9000 MB you will eventually fill up your entire hard disk with junk you never use and your machine will grind to a halt. To make matters worse, IE (Internet Explorer) cleverly hides the cached files from view that are causing all the trouble. Especially on Windows 98, to add insult to injury, having too big a cache will slow you down too. 20 to 100 MB is probably sufficient before you reap no additional benefit.

To manually clear the Applet/Jar cache, delete files in:

C:\Documents and Settings\administrator\Application Data\Sun\Java\Deployment\cache\javapi\v1.0\jar
C:\Documents and Settings\administrator\Application Data\Opera\Opera75\profile\cache4

Books

recommend book⇒Web Caching

by:

Duane Wessels

978-1-56592-536-6

paperback

publisher:

O’Reilly

published:

2001-06

The author is the creater of Squid an open-source web caching program. It also tackles such things as why web site owners deliberately foil caching. The author has a refreshingly simple and direct way of writing.

Greyed out stores probably do not have the item in stock

Learning More

Oracle’s Technote Guide on Applet caching : available:

on the web at Oracle.com
in the current JDK 1.7.0_02 on your local Windows J: drive.

expiry header

	You can get the freshest copy of this page from:	or possibly from your local J: drive (Java virtual drive/mindprod.com website mirror)
	http://mindprod.com/jgloss/caching.html	J:\mindprod\jgloss\caching.html
	Please email your feedback for publication, letters to the editor, errors, omissions, typos, formatting errors, ambiguities, unclear wording, broken/redirected link reports, suggestions to improve this page or comments to Roedy Green : If you want your message kept confidential, not considered for posting, please explicitly specify that.
	Canadian Mind Products
	mindprod.com IP:[65.110.21.43]
view Blog	Your face IP:[38.107.179.210]
Feedback	You are visitor number 16,380.