Cache of hibrenate notes

Level 1 cache:

Session cache. When the program calls the SAVE (), upadte (), saveorupdate (), get (), load (), and list () that calls the query interface (), iterator (), filter (). If the object does not exist in the session cache, Hibernate will add the object to the first-level cache,

In addition, the session interface provides two methods:

Evict (Object OBJ): clears the persistence object specified in the cache.

Clear (): clears all cached objects.

Secondary cache:

It is a pluggable cache plug-in managed by sessionfactory, but note that concurrency problems may occur.

Usage:

1. Rarely modified data

2. Not very important data, allowing occasional Concurrent Data

3. data that will not be accessed concurrently

4. Limited instances are referenced in many places

Cache plug-ins:

Cache plug-in	Hibernate implementation class	Save type	Cluster	Query
Ehcach	Org. hibernate. cache. ehcachprovider	Memory, Hard Disk	N	Y
Oscach	Org. hibernate. cache. oscachprovider	Memory, Hard Disk	N	Y
Swarmcach	Org. hibernate. cache. swarmcacheprovider	Cluster	Y	N
JBoss treecach	Org. hibernate. cache. treecacheprovider	Cluster	Y	Y

Cache plug-in	Read-Only Type	Non-strict read/write type	Read/write type	Transaction type
Ehcach	Y	N	Y	N
Oscach	Y	N	Y	N
Swarmcach	Y	Y	N	N
JBoss treecach	Y	N	N	Y

Second-level Cache Usage:

1. Set cache granularity and concurrent Access Policy

Hibernate allows you to set a level-2 cache at the granularity of classes and sets.

Xxx. HBM. xml file

Class:

<Class name = "" table = "" catalog = "hbql">

<Cache Usage = "read-write">

....

</Class>

Set:

<Class name = "A" table = "" catalog = "hbql">

<Cache Usage = "read-write"> <! -- Set a concurrent access policy for usage -->

<Set name = "B" cascade = "Save-Update" inverse = "true">

<Cache Usage = "read-write"> with this part added, the B object associated with object A will not be placed in the second-level cache, but can be normally set.

....

</Set>

....

</Class>

2. Select the second-level cache plug-in

Hibernate. cfg. xml

<Session-factory>

<Property name = "hibernate. cache. provider_class">

Org. hibernate. cache. ehcachprovider

</Property>

.....

</Session-factory>

Cache attributes

Attribute name	Description
Hibernate. cache. provider_class	Cache Class Name
Hibernate. cache. use_minimal_puts	Cluster useful
Hibernate. cache. use_query_cache	Query Cache
Hibernate. cache. use_second_level_cache	Enable Level 2 cache?
Hibernate. cache. region_prefix	Prefix of the second-level cache region name
Hibernate. cache. use_structured_entries	Force hibernate to store the second-level cache in a certain format

Level 3 cache:

Also called query Cache

When the first query is performed, the results are placed in the second-level cache.

Usage:

1. Frequently queried query statements

2. Rarely modify the query-related data

Usage:

Load () method: Execution Process: Level 1 cache-> Level 2 Cache-> delayed loading-> database (with delayed loading configured, a proxy class is returned)

Get () does not use query Cache

List (): The first query will be filled. Three Levels of cache will return the value. If the obtained value is ID, the value will be queried by ID for a long time... data changes cache automatically cleared... it may cause n queries

Iterator (): first obtain the ID, and then use load ()

NOTE: If some columns of the select object, the entire result set will be cached... if the query result is a collection of object objects, only the id value of the object will be cached.

1. Configure the second-level cache

2. Start query Cache

<Property name = "cache. use_query_cache"> true </property>

3. Use in the program

Query. setcacheable (true );

Query. setcacheregion ("mycacheregion") // if not set, the standard region is used by default.