What is Hibernate Caching

What is Hibernate Caching?

Caching functionality is designed to reduce the amount of necessary database access. When the objects that are cached reside in memory. You have the flexibility to limit the usage of memory and store the items in disk storage. The implementation will depend on the underlying cache manager.

1. FirstLevel Cache
1. First-level cache always Associates with the Session object. Hibernate uses this cache by default. Here, it processes one transaction after another one, means won't process one transaction many times. Mainly it reduces the number of SQL queries it needs to generate within a given transaction. That is instead of updating after every modification done in the transaction, it updates the transaction only at the end of the transaction.
2. Second Level Cache
1. Second-level cache always associates with the Session Factory object. While running the transactions, in between it loads the objects at the Session Factory level, so that those objects will available to the entire application, don’t bounds to single user. Since the objects are already loaded in the cache, whenever an object is returned by the query, at that time no need to go for a database transaction. In this way the second level cache works.
3. Query Cache
1. Query Cache is used to cache the results of a query. When the query cache is turned on, the results of the query are stored against the combination query and parameters. Every time the query is fired the cache manager  checks for the combination of parameters and query. If the results are found in the cache, they are returned, otherwise a database transaction is initiated.  As you can see, it is not a good idea to cache a query if it has a number of parameters, because then a single parameter can take a number of values. For each of these combinations the results are stored in the memory. This  can lead to extensive memory usage.