Hibernate---Three states of an object

Hibernate---Three states of an object

　　In short, Hibernate is an object-oriented ORM-based framework that is located in the DAO layer and is a framework for manipulating data. I'll talk about the three states of Hibernate objects. They were: free, persistent and instantaneous. Use the code to explain it.

Hibernate.cgf.xml

<?xml version= "1.0" encoding= "UTF-8"? ><! DOCTYPE hibernate-configuration Public "-//hibernate/hibernate configuration DTD 3.0//en" "Http://www.hibern Ate.org/dtd/hibernate-configuration-3.0.dtd ">
  User.hbm.xml   
 
<?xml version= "1.0" encoding= "UTF-8"? ><! DOCTYPE hibernate-mapping Public "-//hibernate/hibernate mapping DTD 3.0//en" "http://www.hibernate.org/dtd/  Hibernate-mapping-3.0.dtd "><!--ORM Metadata Table Object Relational mapping file package: Configure the packages in this configuration file that are in the same class. -->
User
Package com.huhu.domain;//Hibernatepublic class User {    private Integer ID;    private String name;    private String password;    Public Integer getId () {        return ID;    }    public void SetId (Integer id) {        this.id = ID;    }    Public String GetName () {        return name;    }    public void SetName (String name) {        this.name = name;    }    Public String GetPassword () {        return password;    }    public void SetPassword (String password) {        this.password = password;    }    @Override public    String toString () {        return "User [id=" + ID + ", name=" + name + ", password=" + Password                + "]";    }}
Hibernateutils
package Com.huhu.utils;import Org.hibernate.sessionfactory;import Org.hibernate.cfg.configuration;import org.hibernate.classic.session;//Complete Hibernate tool class//package profile read operation// Package Sessionfactroy Create operation//encapsulation session get Operation public class Hibernateutils {private static sessionfactory sf;static{// 1 Load config Configuration conf = new configuration (). Configure ();//2 create SESSIONFACTORYSF based on configuration information Conf.buildsessionfactory ();//runtime.getruntime (). Addshutdownhook (New Thread (new Runnable () {@Overridepublic void Run () {System.out.println ("virtual institution closed! Release resources"); Sf.close ();}));} public static Org.hibernate.Session Opensession () {//3 gets sessionsession session = Sf.opensession (); return session;} public static Org.hibernate.Session Getcurrentsession () {//3 gets sessionsession Session = Sf.getcurrentsession (); return session;} public static void Main (string[] args) {System.out.println (opensession ());}} 
  HibernateDemo1   
Package Com.huhu.a_state;import Com.huhu.domain.user;import Com.huhu.utils.hibernateutils;import org.hibernate.session;/** * Three states of the object */public class HibernateDemo1 {//three states public void Fun1 () {Session Sessi        On = Hibernateutils.opensession ();        Session.begintransaction ();          --------------------------------------User U = new user ();           Status: Transient state u.setname ("Tom");      Status: Instantaneous state U.setpassword ("1234");            Status: Transient state//Save Session.save (U); Status: Persistent state//When the Save method is called, the database has no corresponding record//no record, but will eventually be synchronized to the database, still persistent state//---------------------------------      -----session.gettransaction (). commit ();            Status: Persistent state session.close ();        Status: Free State}//conversion of three states instantaneous = "Persistent public void Fun2 () {Session session = Hibernateutils.opensession ();        Session.begintransaction ();   --------------------------------------User U = new user ();        Status: Instantaneous state u.setname ("he");     Status: Instantaneous state U.setpassword ("123456");             Status: Instantaneous state session.save (U);      Status: Persistent state//--------------------------------------session.gettransaction (). commit ();        Status: Persistent state//When a transaction commits, the persisted object is saved to the database//increment=>hibernate automatically queries the maximum ID, then generates the primary key//assigned = = automatically generates the primary key    Session.close (); }//instantaneous = "Free instantaneous: no association No ID free: no correlation with ID (id corresponding to database) public void Fun3 () {Session session = Hibernateutils.opensessi        On ();        Session.begintransaction ();        --------------------------------------//status: Persistent state User u = New User ();         U.setid (2);      This is the Free State//--------------------------------------session.gettransaction (). commit ();    Status: Persistent state//The persisted object is saved to the database Session.close () when the transaction commits;      }//persistent = "Instantaneous 1 persistent: associated, with ID, instantaneous: No association without ID public void Fun4 () {Session session = Hibernateutils.opensession ();  Session.begintransaction (); --------------------------------------//status: Persistent state//through the Get method, get the persistent state object user U = (user) session.get (user). class, 2);        Persistent state//--------------------------------------session.gettransaction (). commit ();  The persisted object is saved to the database Session.close () when the transaction commits;    Free State u.setid (NULL);        }//persistent = "Instantaneous 1 persistent: associated, with ID, instantaneous: No association without ID public void Fun5 () {Session session = Hibernateutils.opensession ();        Session.begintransaction (); --------------------------------------//status: Persistent state//through the Get method, get the persistent state object user U = (user) session.get (user). class, 4);       Persistent state session.evict (U);          Removes the U.setid (NULL) from the association of the user object and the session;        Instantaneous object//--------------------------------------session.gettransaction (). commit ();        Session.save (U);  The persisted object is saved to the database Session.close () when the transaction commits; Free State}//persistent = "free persistent: associated with id public void Fun6 () {Session session = HiberNateutils.opensession ();        Session.begintransaction (); --------------------------------------//status: Persistent state//through the Get method, get the persistent state object user U = (user) session.get (user). class, 4);       Persistent state session.evict (U); Removes the association of the user object from the session//--------------------------------------session.gettransaction (). commit ();  Free Session.close ();        Free State}//free = "instantaneous instantaneous: no association without ID public void Fun7 () {Session session = Hibernateutils.opensession ();        Session.begintransaction (); --------------------------------------//status: Persistent state//through the Get method, get the persistent state object user U = (user) session.get (user). class, 4);       Persistent state session.evict (U);          Instantaneous u.setid (null); Instantaneous//--------------------------------------session.gettransaction (). commit ();  Instantaneous session.close ();        Transient state}//free = "is persistent associated with the session public void Fun8 () {Session session = Hibernateutils.opensession (); SeSsion.begintransaction (); --------------------------------------//status: Persistent state//through the Get method, get the persistent state object user U = (user) session.get (user). class, 4);       Persistent state session.evict (U);      Free session.update (u); Durable//--------------------------------------session.gettransaction (). commit ();  Persistent Print Updata statement session.close ();        Transient state} public void Fun9 () {Session session = Hibernateutils.opensession ();        Session.begintransaction ();        --------------------------------------////through the Get method, get the persistent state object User u = (user) Session.get (User.class, 4);        U.setname ("Nenen");        --------------------------------------session.gettransaction (). commit ();  Session.close ();        Transient state} public static void Main (string[] args) {HibernateDemo1 d = new HibernateDemo1 ();        D.fun1 ();    D.fun9 (); }}
The code is obvious. If you don't think it's obvious, take another picture.
　　
　　Let's summarize the following:
　What is the use of three states:
1. Persistent state: We use hibernate primarily to persist data
2. For the state of the object: we expect that the data that we now need to synchronize to the database is converted to persistent
Features of persistent speech objects:
Hibernate automatically synchronizes changes to persistent session objects to the database.

　　So hibernate is an object-oriented framework that leverages the object's operational data.
　　
　
Hibernate---Three states of an object