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. 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 with JDK 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 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

paperback

ISBN13:

978-1-56592-536-6

publisher:

O’Reilly

published:

2001-06

by:

Duane Wessels

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.

	abe books.co.uk	abe books.ca
	amazon.co.uk	amazon.ca
	abe books.de	chapters.indigo.ca
	amazon.de	abe books.com
	abe books.fr	amazon.com
	amazon.fr	barnes and noble.com
	abe books.it	powells.com
	iberlibro.com	sony e-books
	abe books anz	o’reilly safari

Learning More

Sun’s JDK Technote Guide on Applet caching : available:

on the web at java.sun.com
in the current JDK 1.6.0_17 on your local Windows J: drive.

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