Session Description in hibernate

The transparent persistence of hibernate makes it very comfortable to use, and sometimes even forgets the existence of the database. My friends often cannot tell the differences between SAVE, saveorupdate, and update. Lock, merge, replicate, refresh, and evict do not even know what to do. In addition, there are many concepts about the lifecycle of object, but the differences between transient, persistent, and detached are not clear. I just know the popular names such as po and vo. In fact, these concepts are very simple, and hibernate's javadoc is clearly written. You only need to look at it to understand it. So I spent some time translating the javadoc part of the session in hibernate 3.1.2 to let those who forget its basic concepts because of hibernate's "Transparency" and then look at these concepts.

Org. hibernate
Interface session

All superinterfaces:

Serializable

All known subinterfaces:

Eventsource, session

All known implementing classes:

Sessionimpl

Public interface Session

Extends serializable

Java applicationsProgramAnd the main runtime interface between hibernate. It is the core abstract API class that abstracts the concept of persistent service.

SessionIs bound to a physical transaction (tansaction. (Long transactions may span multiple database transactions .)

SessionThe main function is to create, read, and delete ing object class instances. The instance may exist in the following three States:

Free Status (transient ):No persistence, noSessionAssociated
Persistent ):OnlySessionAssociated
Detached ):Persistence has been performed, but not with anySessionAssociated

Instances in the free status can be called by callingSave (),Persist ()OrSaveorupdate ()Method for persistence. Persistent instances can be called by callingDelete ()Changes to the Free State. PassGet ()OrLoad ()The instances obtained by the method are all persistent. Instances in the free status can be called by callingUpdate (), 0Saveorupdate (),Lock ()OrReplicate ()For persistence. Instances in the free or free state can be calledMerge ()Method to become a new persistent instance.

Save ()AndPersist ()SQLInsert,Delete ()SQLDelete, AndUpdate ()OrMerge ()SQLUpdate. PairPersistent)Instance modifications are detected during refresh and submission, which also causes SQLUpdate.Saveorupdate ()OrReplicate ()SQLInsertOrUpdate.

Its implementation is not necessarily thread-safe. Each thread/transaction should be fromSessionfactoryObtain your own session instance.

If its Persistent Object Class is serializableSessionThe instance is also serializable.

A typical transaction should use the following format:

 
Session sess = factory. opensession (); transaction TX; try {Tx = sess. begintransaction (); // do some work... TX. commit ();} catch (exception e) {If (TX! = NULL) Tx. rollback (); throw E;} finally {sess. Close ();}
 

IfSessionIf an exception is thrown, the transaction must be rolled back and the session will be discarded. After an exception occursSessionThe internal status of may be out of sync with the database.

 

 

Author:

Gavin king

See also:

Sessionfactory

Method Summary
Transaction	Begintransaction() Starts a work unit and returns the associatedTransaction)Object.
Void	Cancelquery() Terminate the current query.
Void	Clear() Completely clear this session.
Connection	Close() Stop thisSessionBy interrupting the JDBC connection and clearing it.
Connection	Connection() Obtain the JDBC connection of this session. If this session uses an active collection release policy (for example, CMT-container controls the transaction environment), the current application is responsible for closing the connection to this call.
Boolean	Contains(Object object) Check whether the object instance matches the currentSessionAssociation (whether it is in the persistent State ).
Criteria	Createcriteria(Class persistentclass) Creates a newCriteriaInstance.
Criteria	Createcriteria(Class persistentclass, string alias) Creates a new object based on the given object class or its superclass.CriteriaInstance, and assign it (entity class) an alias.
Criteria	Createcriteria(String entityname) Creates a new object based on the name of the given object.CriteriaInstance.
Criteria	Createcriteria(String entityname, string alias) Creates a new object based on the name of the given object.CriteriaInstance, and assign it (entity class) an alias
Query	Createfilter(Object collection, string querystring) Creates a newQueryInstance.
Query	Createquery(String querystring) Creates a new hql query condition.QueryInstance.
Sqlquery	Createsqlquery(String querystring) Create a newSqlqueryInstance.
Void	Delete(Object object) Removes an instance of a persistent object from a database.
Void	Delete(String entityname, object) Removes an instance of a persistent object from a database.
Void	Disablefilter(String filtername) Disable the name filter of the current session.
Connection	Disconnect() DisconnectedSessionAnd the current JDBC connection.
Filter	Enablefilter(String filtername) Open the name filter of the current session.
Void	Evict(Object object) Clears the current object instance from the session cache.
Void	Flush() Force commit refresh (flush)Session.
Object	Get(Class clazz, serializable ID) Returns the instance of the Persistent Object Based on the given identifier and object class. If no persistence object instance meets the condition, null is returned.
Object	Get(Class clazz, serializable ID, lockmode) Returns the instance of the Persistent Object Based on the given identifier and object class. If no persistence object instance meets the condition, null is returned.
Object	Get(String entityname, serializable ID) Returns the persistence instance that matches the given object name and identifier. If no persistence instance is matched, null is returned.
Object	Get(String entityname, serializable ID, lockmode) Returns the persistence instance that matches the given object class and identifier. If no persistence instance exists, null is returned.
Cachemode	Getcachemode() Obtain the current cache mode.
Lockmode	Getcurrentlockmode(Object object) Checks the current lock level of a given object.
Filter	Getenabledfilter(String filtername) Obtain a filter based on the name ).
Entitymode	Getentitymode() Obtains the effective entity mode of this session.
String	Getentityname(Object object) Returns the Object Name of a persistent object.
Flushmode	Getflushmode() Obtain the current flush mode.
Serializable	Getidentifier(Object object) Obtain the given object instance inSessionIf the instance is in the free status (transient) orSessionAssociation throws an exception.
Query	Getnamedquery(String queryname) ObtainsQuery)Instance.
Session	Getsession(Entitymode) Starts a new valid session based on the given entity mode.
Sessionfactory	Getsessionfactory() ObtainSessionfactoryInstance.
Sessionstatistics	Getstatistics() Obtains the statistics of this session.
Transaction	Gettransaction() ObtainTransaction)Instance. Instance associated with this session.
Boolean	Isconnected() Check the currentSessionWhether it is in the connection status.
Boolean	Isdirty() CurrentSessionIs there any changes (data status) that need to be synchronized with the database? If we refresh the Commit (flush) session, will there be SQL Execution?
Boolean	Isopen() Check the currentSessionWhether or not it is still enabled.
Object	Load(Class theclass, serializable ID) If a qualified instance exists, a persistent instance is returned Based on the given entity class and identifier.
Object	Load(Class theclass, serializable ID, lockmode) If a qualified instance exists, a persistent instance is returned Based on the given entity class, identifier, and specified lock level.
Void	Load(Object object, serializable ID) Copy the persistent state (value) corresponding to the given identifier to the given trasient instance.
Object	Load(String entityname, serializable ID) If a qualified instance exists, a persistent instance is returned Based on the given entity class and identifier.
Object	Load(String entityname, serializable ID, lockmode) If a qualified instance exists, a persistent instance is returned Based on the given entity class, identifier, and specified lock level.
Void	Lock(Object object, lockmode) Obtain the specified lock level from a given object.
Void	Lock(String entityname, object, lockmode) Obtain the specified lock level from a given object.
Object	Merge(Object object) Copy the status of a given object to a persistent object with the same identifier.
Object	Merge(String entityname, object) Copy the status of a given object to a persistent object with the same identifier.
Void	Persist(Object object) Persists an instance in the Free State (transient.
Void	Persist(String entityname, object) Persists an instance in the Free State (transient.
Void	Reconnect() Not recommended. Manual reconnection is only applicable when applications provide connections. In this case, you may need to useReconnect (Java. SQL. Connection).
Void	Reconnect(Connection) Reconnect to the specified JDBC connection.
Void	Refresh(Object object) Reads the status of a given instance from the database.
Void	Refresh(Object object, lockmode) Based on the specifiedLock mode)To re-read the status of a given instance from the database.
Void	Replicate(Object object, replicationmode) Uses the current Identifier value to persist the given free state (transient) entity.
Void	Replicate(String entityname, object, replicationmode) Uses the current Identifier value to persist the given free state (transient) entity.
Serializable	Save(Object object) First, generate an identifier for the given free state (transient) object (according to the configuration) and assign a value, and then make it persistent.
Serializable	Save(String entityname, object) First, generate an identifier for the given free state (transient) object (according to the configuration) and assign a value, and then make it persistent.
Void	Saveorupdate(Object object) Based on the value of the Identity attribute of the given instance (Note: unsaved-value can be specified. The default value is null .) To determine the executionSave ()OrUpdate ()Operation.
Void	Saveorupdate(String entityname, object) Based on the value of the Identity attribute of the given instance (Note: unsaved-value can be specified. The default value is null .) To determine the executionSave ()OrUpdate ()Operation.
Void	Setcachemode(Cachemode) Set the refresh submission mode.
Void	Setflushmode(Flushmode) Set the refresh submission mode.
Void	Setreadonly(Object entity, Boolean readonly) Set an unchanged Persistent Object to read-only mode, or mark a read-only object as a mode that can be modified.
Void	Update(Object object) Update the persistent instance based on the ID of the specified detached (idle state) object instance.
Void	Update(String entityname, object) Update the persistent instance based on the ID of the specified detached (idle state) object instance.