HashMap caching stale data

[kri shan]

Using HashMap as caching (not using JBoss cache/ coherence caching) to store large number of records from DB. How should I find stale data, if DB records are updated.

[Tim Cooke]

Trying to roll your own database cache is fraught with danger. You question about purging stale items is just the tip of the iceberg.

Use an "off the shelf" caching framework such as ehcache.

[Campbell Ritchie]

Why are you caching in the first place, if you use a DB?

[kri shan]

Why are you caching in the first place, if you use a DB?

To avoid multiple calls to DB.

Use an "off the shelf" caching framework such as ehcache.

We should not use any caching framework.

[Campbell Ritchie]

kri shan wrote: . . . To avoid multiple calls to DB. . . .

Why? If your database has been updated, you will be using stale data.

[Tim Cooke]

We should not use any caching framework.

This seems like an unreasonable restriction. Given the fact that you are intending to implement your own caching framework anyway, why not use one that already exists?

[Campbell Ritchie]

Tim Cooke wrote: . . . This seems like an unreasonable restriction. . . .

It is unreasonable, unless the exercise is about creating caching frameworks.

[William Brogden]

People have been writing "open source java cache" toolkits since Java 1.02 - do that google search, check out the design parameters other people have used, grab some example code to see how they did it.

Bill