2.1 Caching overview
In the computer science world, a cache is a special high-speed mechanism for storing and retrieving data. Two types of caching are commonly used:
| 
|
| Memory-based caching |
|
|
|
| Disk-based caching |
Caching techniques are implemented by system designers to improve application response times and reduce system load. Caching methodologies have long been used to improve the performance of Internet applications. In caching parlance, any request that can be satisfied directly by data held in a cache is termed a cache hit. The effectiveness of a cache is judged by its hit rate.
The strategies for determining what information should be kept in the cache constitute some of the more interesting problems that a J2EE architect may encounter.
Principally, the concerns of a cache designer are:
|
|
|
| How to get data into the cache. |
|
|
|
| How to retrieve cached items quickly. |
|
|
|
| What happens if cached data becomes invalid? |
|
|
|
| How to remove invalid cache items. |