Hibernate primary Key generation policy

First step: Introduce the jar package omission

Part II: Creating an entity class

Package Cn.hibernate.bean;

public class Student {

private Integer sId;
private String sName;
Public Integer GetSID () {
return sId;
}
Public void Setsid (Integer sId) {
this.sid = sId;
}
Public String Getsname () {
return sName;
}
Public void Setsname (String sName) {
this.sname = sName;
}
Public Student (Integer sId, String sName) {
super ();
this.sid = sId;
this.sname = sName;
}
Public Student () {
super ();
}
@Override
Public String toString () {
return "Student [sid=" + SId + ", sname=" + SName + "]";
}

}

Step three: Create a mapping file Student.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" >

<class name= "Student" >
<id name= "SId" >
<!--
primary key generation policy
* Shaping: Int/short/long
1.increment:hiernate The primary key in the Automatic maintenance table, query Max (ID) First, then the maximum value +1, execute the INSERT statement
There is a concurrency problem and it is not recommended
the 2.identity,hibernate is automatically normal with the database underlying. Example: MySQL # # auto_increment modifier primary KEY
"auto--increment=5" exists in the table structure of the database for logging
The 3.sequence,hibernate uses the database underlying sequence. Example: Oracle
Oracle: Automatic enhancement not supported, but sequence supported
4.hilo,hibernate will use the high-low algorithm (High/low) for data that does not know about this autogrow and sequence (understand it)
thought: Using another table to record the accumulated data
<generator class= "Hilo" >
<param name= "table" >hi_value</param> hi_value another table indicates
<param name= "column" >next_value</param> next_value another table field name
<param name= "Max_lo" >100</param> the maximum number of concurrent operations supported by a single operation.
</generator>
Batch First value: Max_lo * next_value + next_value
6 + 6
5.native: Select one from identity, sequence, Hilo, according to database decision
# # #以上的类型都是整形
6.UUID, type must be string
above policy: Hibernate auto Generation: Proxy primary key
7.assigned: Natural primary key, the program set itself.
-
<generator class= "Assigned" >
</generator>
</id>
<property name= "SName" ></property>
</class>

Fourth step: Create a Hibernate.cfg.xml file

<?xml version= "1.0" encoding= "UTF-8"?>
<! DOCTYPE hibernate-configuration Public
"-//hibernate/hibernate Configuration DTD 3.0//en"
"HTTP://WWW.HIBERNATE.ORG/DTD/HIBERNATE-CONFIGURATION-3.0.DTD" >

<session-factory>
<!--#1 basic four items
Property.Name value if you start with ' hibernate ', you can omit
same as "Hibernate.connection.driver_class" and "Connection.driver_class"
-
<property name= "Hibernate.connection.driver_class" >
Com.mysql.jdbc.Driver
</property>
<property name= "Hibernate.connection.url" >
Jdbc:mysql://localhost:3306/minemysql
</property>
<property name= "Hibernate.connection.username" >root</property>
<property name= "Hibernate.connection.password" >root</property>

<!--#2方言-
<property name= "Hibernate.dialect" >
Org.hibernate.dialect.MySQLDialect
</property>


<!--#3 SQL --
<!--whether to display SQL statements --
<property name= "Hibernate.show_sql" >true</property>
<!--whether formatted SQL statements do not format the display of a row formatted to display multiple lines--
<property name= "Hibernate.format_sql" >true</property>
<!--Whether a comment is displayed, providing the current SQL statement action Object--
<property name= "hibernate.use_sql_comments" >true</property>


<!--#4如何创建表 (not important)
Create : Each time the Cfg.xml file is loaded, the table will be created, and when the program is closed, the table is not deleted [initialized, used during testing]
If the table exists, it is first deleted and then created
Create-drop: Each time the Cfg.xml file is loaded, the table is created and the table is deleted when the program closes
Factory.close () must be executed to delete
Update: If the table does not exist then create, if the table exists, first check whether the *.hbm.xml file matches the table,
if the mismatch will update the table structure (add only, do not delete)
Validate: Load cfg.xml validation, map file and data table match, if match normal operation, if not match throw exception
# # # shows the development of the first table, and then the mapping file
* Table created by DBA
-
<property name= "Hibernate.hbm2ddl.auto" >update</property>


<!--#5取消bean效验-
<property name= "Javax.persistence.validation.mode" >none</property>
</session-factory>

Fifth step: Create a Test class

Package cn.hibernate.test;

Import org.hibernate.Session;
Import Org.hibernate.SessionFactory;
Import org.hibernate.cfg.Configuration;
Import Org.junit.Test;

Import cn.hibernate.bean.Student;

Public class Teststu {

private Sessionfactory factory = new Configuration (). Configure (). addclass (Student.class). Buildsessionfactory ();

@Test
Public void Demo01 () {
/*
* Test increment in the primary key generation strategy
* */

Session session = Factory.opensession ();
session.begintransaction ();

Student stu = new Student ();
stu.setsname ("haha");
Session.save (stu);
session.gettransaction (). commit ();
session.close ();

//Execute the statement
/*hibernate:
Select
Max (sId)
from
Student
Hibernate:
Insert Cn.hibernate.bean.Student
Insert
into
Student
(SName, sId)
Values
(?, ?) */

}


@Test
Public void Demo02 () {
/*
* Test the identity in the primary key generation policy
* */

Session session = Factory.opensession ();
session.begintransaction ();

Student stu = new Student ();
stu.setsname ("haha 1");
Session.save (stu);
session.gettransaction (). commit ();
session.close ();

//Execute the statement
/*hibernate:
Insert Cn.hibernate.bean.Student
Insert
into
Student
(SName)
Values
(?)
*/

}


@Test
Public void demo03 () {
/*
* Test the Hilo in the primary key generation strategy
* */

Session session = Factory.opensession ();
session.begintransaction ();

Student stu = new Student ();
stu.setsname ("haha");
Session.save (stu);

Student stu1 = new Student ();
stu.setsname ("haha");
Session.save (STU1);

Student stu2 = new Student ();
stu.setsname ("haha");
Session.save (STU2);

session.gettransaction (). commit ();
session.close ();

}

@Test
Public void demo04 () {
/*
* Test the UUID in the primary key generation strategy
* */

Session session = Factory.opensession ();
session.begintransaction ();

Student stu = new Student ();
stu.setsname ("333");
Session.save (stu);

Student stu1 = new Student ();
stu.setsname ("222");
Session.save (STU1);

Student stu2 = new Student ();
Stu.setsname ("111");
Session.save (STU2);

session.gettransaction (). commit ();
session.close ();

}

@Test
public void demo05 () {
/*
* Test assigned in the primary key generation strategy
* */

Session session = Factory.opensession ();
Session.begintransaction ();

Student stu = new Student ();
Stu.setsid ("104322-19910423-ww");
Stu.setsname ("333");
Session.save (Stu);

Session.gettransaction (). commit ();
Session.close ();

}

}

Hibernate primary Key generation policy