7.3 Hibernate: Built-in builder--GUID

Uses a GUID generated by a database of type string.

guid:globally Unique Identifier, a globally unique identifier, also known as a UUID, is a 128-bit long number, expressed as a 16 binary. The core idea of the algorithm is to combine the machine's NIC, local time, and a random number to generate GUIDs.

Hibernate queries the database before maintaining the primary key, obtaining a UUID string, the primary key value. This value is unique, with the disadvantage of being large in length and limited in supported databases, with the benefit of cross-database but still requiring access to the database.

Note: The length varies depending on the database. MySQL uses the Select UUID () statement to get a 36-bit string (standard format containing "-") using the Select Rawtohex (Sys_guid ()) from DUAL statement in Oracle to obtain a 32-bit string (not Include "-")

Features: Need database support query UUID, generate the need to query the database, efficiency without UUID high, recommended to use UUID.

Using MySQL Demo: 1 using XML

1.1 Persistence class Definition:

Package hibernate;

Import Java.util.Date;

    public class Person {private String ID;

    Private String account;

    private String name;

    Private Date birth;
        Public person () {} public person (string account, string name, Date birth) {this.account = account;
        THIS.name = name;
    This.birth = birth;
    } public String GetId () {return id;
    } public void SetId (String id) {this.id = ID;
    } public String Getaccount () {return account;
    The public void Setaccount (String account) {this.account = account;
    } public String GetName () {return name;
    } public void SetName (String name) {this.name = name;
    Public Date Getbirth () {return birth;
    } public void Setbirth (Date birth) {This.birth = birth; } @Override Public String toString () {return ' person [id= + ID + ', account= ' + account + ', name= "+ N Ame+ ", birth=" + Birth + "]"; }

}

Note: The GUID generated by MySQL is a 36-bit standard UUID string with "-", so the persisted class primary key is defined as a string type, and the mapping file needs to be consistent.

1.2 Defining Mappings:

<?xml version= "1.0"?>
<! DOCTYPE hibernate-mapping Public "-//hibernate/hibernate mapping DTD 3.0//en"
"http://hibernate.sourceforge.net/ Hibernate-mapping-3.0.dtd ">
 
1.3 Unit Test:

package hibernate;

Import Java.util.Date;
Import org.hibernate.Session;
Import Org.hibernate.SessionFactory;
Import org.hibernate.Transaction;
Import org.hibernate.cfg.Configuration;

Import Org.junit.Test; public class Hibernatetest {@Test public void Test () {Configuration configuration = new configuration ()
        . Configure ("Hibernate.cfg.xml");
        Sessionfactory sessionfactory = Configuration.buildsessionfactory ();
        Session session = Sessionfactory.opensession ();
        Transaction Transaction = Session.begintransaction ();
        Date date = new Date (System.currenttimemillis ());
        Person Person1 = new Person ("Admin1", "Nick", date);
        Session.save (Person1);
        Person Person2 = new Person ("admin2", "King", date);
        Session.save (Person2);
        Transaction.commit ();
        Session.close ();
    Sessionfactory.close (); }

}
 
The unit test passes, querying the database for newly inserted data:
2 using annotations (annotation)

To define a persistence class using annotations:

Package hibernate;

Import Java.util.Date;
Import javax.persistence.Entity;
Import Javax.persistence.GeneratedValue;
Import Javax.persistence.Id;

Import javax.persistence.Table;

Import Org.hibernate.annotations.GenericGenerator; @Entity @Table public class Person {@Id @GeneratedValue (generator = "Assignedgenerator") @GenericGenerator (n

    Ame = "Assignedgenerator", strategy = "GUID") private String ID;

    Private String account;

    private String name;

    Private Date birth;
        Public person () {} public person (string account, string name, Date birth) {this.account = account;
        THIS.name = name;
    This.birth = birth;
    } public String GetId () {return id;
    } public void SetId (String id) {this.id = ID;
    } public String Getaccount () {return account;
    The public void Setaccount (String account) {this.account = account;
 } public String GetName () {return name;   } public void SetName (String name) {this.name = name;
    Public Date Getbirth () {return birth;
    } public void Setbirth (Date birth) {This.birth = birth; } @Override Public String toString () {return ' person [id= + ID + ', account= ' + account + ', name= "+ N
    Ame + ", birth=" + Birth + "]"; }

}
 
 Run the 1.3 unit test and the test results are the same.