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四、ID生成策略

第一种：XML配置ID

第二种：Annotation配置ID

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Jun 07, 2016 pm 04:13 PM

hibernate xml generate Strategy match

四、ID生成策略第一种：XML配置ID 通过为id元素增加generator子元素，该子元素拥有class属性。常用的class属性有: (1)increment:用于为long、short、或者int类型生成唯一标识。只有在没有其他进程往同一张表中插入数据的时候才能使用。在集群不要使用。（极

四、ID生成策略

第一种：XML配置ID

通过为元素增加子元素，该子元素拥有class属性。常用的class属性有:

(1)increment:用于为long、short、或者int类型生成唯一标识。只有在没有其他进程往同一张表中插入数据的时候才能使用。在集群不要使用。（极少使用）

(2)native：让数据库自动选择identity，sequence，或者其他。

(3)uuid:128位的UUID算法，产生String类型ID

(4)identity：对于DB2、MySQL、SQL Server、Sybase和HypersonicSQL的内置标识字段提供支持。返回的标识符是long、short或者int类型。

sequence:在Oracel，PostgreSQL，SAP，DB，Mckio中使用序列（sequence），而在Interbase中使用生成器（generator），返回的标识符是long、short或者是int类型。

小实验1：

（1）创建Student.java

package com.zgy.hibernate.model;
 
public class Student {
 
private String id;
 
private String name;
 
private int age;
 
private int score;
 
public int getScore() {
 
return score;
 
}
 
public void setScore(int score) {
 
this.score = score;
 
}
 
public String getId() {
 
return id;
 
}
 
public void setId(String id) {
 
this.id = id;
 
}
 
public String getName() {
 
return name;
 
}
 
public void setName(String name) {
 
this.name = name;
 
}
 
public int getAge() {
 
return age;
 
}
 
public void setAge(int age) {
 
this.age = age;
 
}
 
}

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（2）在Student.hbm.xml中，为配置其generator的class为uuid

<?xml version="1.0"?>
 
<!DOCTYPE hibernate-mapping PUBLIC
 
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
 
<hibernate-mapping package="com.zgy.hibernate.model">
 
<class name="Student" table="student">
 
<id name="id" column="id">
 
<generator class="uuid"></generator>
 
</id>
 
<property name="name" column="name"></property>
 
<property name="age" column="age"></property>
 
<property name="score" column="score"></property>
 
</class>
 
</hibernate-mapping>

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（3）测试

package com.zgy.hibernate.model;
 
import static org.junit.Assert.*;
 
import java.util.Date;
 
import org.hibernate.Session;
 
import org.hibernate.SessionFactory;
 
import org.hibernate.cfg.AnnotationConfiguration;
 
import org.junit.AfterClass;
 
import org.junit.BeforeClass;
 
import org.junit.Test;
 
public class HibernateIDTest {
 
public static SessionFactory sf = null;
 
@BeforeClass
 
public static void beforeClass(){
 
sf = new AnnotationConfiguration().configure().buildSessionFactory();
 
}
 
@Test
 
public void testStudent() {
 
Student s = new Student();
 
s.setName("张三");
 
s.setAge(20);
 
s.setScore(90);
 
Session session = sf.openSession();
 
session.beginTransaction();
 
session.save(s);
 
session.getTransaction().commit();
 
session.close();
 
}
 
@AfterClass
 
public static void afterClass(){
 
sf.close();
 
}
 
}

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（4）验证

select * from student;
 
+-----------------------------------------------+--------+------+------+
 
| id | name | age | score |
 
+------------------------------------------------+------+-------+------+
 
| 4028dae54aa322d1014aa322d5a50000 | 张三 | 20 | 90 |
 
+----------------------------------+------+-----+-------+------+------+
 
desc student;

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数据插入成功，id类型为varchar(255)，主键

小实验2：

（1）修改Student.java。将id修改为int类型

package com.zgy.hibernate.model;
 
public class Student {
 
private int id;
 
private String name;
 
private int age;
 
private int score;
 
public int getScore() {
 
return score;
 
}
 
public void setScore(int score) {
 
this.score = score;
 
}
 
public int getId() {
 
return id;
 
}
 
public void setId(int id) {
 
this.id = id;
 
}
 
public String getName() {
 
return name;
 
}
 
public void setName(String name) {
 
this.name = name;
 
}
 
public int getAge() {
 
return age;
 
}
 
public void setAge(int age) {
 
this.age = age;
 
}
 
}

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（2）在Student.hbm.xml中，为配置其generator的class为native

<?xml version="1.0"?>
 
<!DOCTYPE hibernate-mapping PUBLIC
 
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
 
<hibernate-mapping package="com.zgy.hibernate.model">
 
<class name="Student" table="student">
 
<id name="id" column="id">
 
<generator class="native"></generator>
 
</id>
 
<property name="name" column="name"></property>
 
<property name="age" column="age"></property>
 
<property name="score" column="score"></property>
 
</class>
 
</hibernate-mapping>

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（3）测试(删除student表)

（4）验证

select * from student;
 
+----+------+-------+-------+
 
| id | name | age | score |
 
+----+------+-------+-------+
 
| 1 | 张三 | 20 | 90 |
 
+----+------+-----+--------+
 
desc student;

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数据插入成功，id为int(11)类型，主键，Auto_increment

第二种：Annotation配置ID

@GeneratedValue，默认的策略是auto,auto相当于XML中配置的native。

小实验1：

（1）编写Teacher.java。在getId()方法上添加@GeneratedValue

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package com.zgy.hibernate.model;
 
import java.util.Date;
 
import javax.annotation.Generated;
 
import javax.persistence.Column;
 
import javax.persistence.Entity;
 
import javax.persistence.EnumType;
 
import javax.persistence.Enumerated;
 
import javax.persistence.GeneratedValue;
 
import javax.persistence.Id;
 
import javax.persistence.Table;
 
import javax.persistence.Temporal;
 
import javax.persistence.TemporalType;
 
import javax.persistence.Transient;
 
@Entity
 
@Table(name="_teacher")
 
public class Teacher {
 
private int id;
 
private String name;
 
private String title;
 
private String address;
 
private String wifeName;
 
private Date birth;
 
private ZhiCheng zhiCheng;
 
@Id
 
@GeneratedValue
 
public int getId() {
 
return id;
 
}
 
public void setId(int id) {
 
this.id = id;
 
}
 
@Column(name="_name")
 
public String getName() {
 
return name;
 
}
 
public void setName(String name) {
 
this.name = name;
 
}
 
public String getTitle() {
 
return title;
 
}
 
public void setTitle(String title) {
 
this.title = title;
 
}
 
public String getAddress() {
 
return address;
 
}
 
public void setAddress(String address) {
 
this.address = address;
 
}
 
public String getWifeName() {
 
return wifeName;
 
}
 
public void setWifeName(String wifeName) {
 
this.wifeName = wifeName;
 
}
 
@Temporal(TemporalType.DATE)
 
public Date getBirth() {
 
return birth;
 
}
 
public void setBirth(Date birth) {
 
this.birth = birth;
 
}
 
@Enumerated(EnumType.STRING)
 
public ZhiCheng getZhiCheng() {
 
return zhiCheng;
 
}
 
public void setZhiCheng(ZhiCheng zhiCheng) {
 
this.zhiCheng = zhiCheng;
 
}
 
}

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（2）编写TeacherTesting.java，用于测试

package com.zgy.hibernate.model;
 
import static org.junit.Assert.*;
 
import java.util.Date;
 
import org.hibernate.Session;
 
import org.hibernate.SessionFactory;
 
import org.hibernate.cfg.AnnotationConfiguration;
 
import org.hibernate.cfg.Configuration;
 
impo【本文来自鸿网互联 (http://www.68idc.cn)】rt org.junit.AfterClass;
 
import org.junit.BeforeClass;
 
import org.junit.Test;
 
public class TeacherTesting {
 
public static SessionFactory sf = null;
 
@BeforeClass
 
public static void beforeClass(){
 
sf = new AnnotationConfiguration().configure().buildSessionFactory();
 
}
 
@Test
 
public void test() {
 
Teacher t = new Teacher();
 
t.setName("t1");
 
t.setTitle("高级");
 
t.setAddress("北京");
 
t.setBirth(new Date());
 
t.setZhiCheng(ZhiCheng.A);
 
Session session = sf.openSession();
 
session.beginTransaction();
 
session.save(t);
 
session.getTransaction().commit();
 
session.close();
 
}
 
@AfterClass
 
public static void afterClass(){
 
sf.close();
 
}
 
}

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（3）验证

select * from _teacher;
 
desc _teacher;

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数据插入成功，id为int(11)，主键，auto_increment

在使用Annotation的时候，除了使用auto策略，还可以使用increment,identity,sequence,table等等。

小实验2：

（1）修改Teacher.java.修改策略为identity

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package com.zgy.hibernate.model;
 
import java.util.Date;
 
import javax.annotation.Generated;
 
import javax.persistence.Column;
 
import javax.persistence.Entity;
 
import javax.persistence.EnumType;
 
import javax.persistence.Enumerated;
 
import javax.persistence.GeneratedValue;
 
import javax.persistence.GenerationType;
 
import javax.persistence.Id;
 
import javax.persistence.Table;
 
import javax.persistence.Temporal;
 
import javax.persistence.TemporalType;
 
import javax.persistence.Transient;
 
@Entity
 
@Table(name="_teacher")
 
public class Teacher {
 
private int id;
 
private String name;
 
private String title;
 
private String address;
 
private String wifeName;
 
private Date birth;
 
private ZhiCheng zhiCheng;
 
@Id
 
@GeneratedValue(strategy=GenerationType.IDENTITY)
 
public int getId() {
 
return id;
 
}
 
public void setId(int id) {
 
this.id = id;
 
}
 
@Column(name="_name")
 
public String getName() {
 
return name;
 
}
 
public void setName(String name) {
 
this.name = name;
 
}
 
public String getTitle() {
 
return title;
 
}
 
public void setTitle(String title) {
 
this.title = title;
 
}
 
public String getAddress() {
 
return address;
 
}
 
public void setAddress(String address) {
 
this.address = address;
 
}
 
public String getWifeName() {
 
return wifeName;
 
}
 
public void setWifeName(String wifeName) {
 
this.wifeName = wifeName;
 
}
 
@Temporal(TemporalType.DATE)
 
public Date getBirth() {
 
return birth;
 
}
 
public void setBirth(Date birth) {
 
this.birth = birth;
 
}
 
@Enumerated(EnumType.STRING)
 
public ZhiCheng getZhiCheng() {
 
return zhiCheng;
 
}
 
public void setZhiCheng(ZhiCheng zhiCheng) {
 
this.zhiCheng = zhiCheng;
 
}
 
}

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（2）测试

（3）验证

select * from _teacher;
 
desc _teacher;

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使用table策略：

@javax.persistence.TableGenerator(
 
name="Teacher_GEN",
 
table="GENERATOR_TABLE",
 
pkColumnName="pkkey",
 
valueColumnName="pkvalue",
 
pkColumnValue="Teacher",
 
allocationSize=1
 
)

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以上Annotation的意义：首先是定义了一个generator,该generator的名字叫做Teacher_GEN,生成一张表，表名为GENERATOR_TABLE，该表有两个字段，分别为pkColumnName和valueColumnName。这个表的第一条数据是：Teacher ， 1。其下一条数据的步长值，即Teacher表的下一条数据的值会是2

小实验3：

（1）修改Teacher.java类

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package com.zgy.hibernate.model;
 
import java.util.Date;
 
import javax.annotation.Generated;
 
import javax.persistence.Column;
 
import javax.persistence.Entity;
 
import javax.persistence.EnumType;
 
import javax.persistence.Enumerated;
 
import javax.persistence.GeneratedValue;
 
import javax.persistence.GenerationType;
 
import javax.persistence.Id;
 
import javax.persistence.Table;
 
import javax.persistence.Temporal;
 
import javax.persistence.TemporalType;
 
import javax.persistence.Transient;
 
@Entity
 
@javax.persistence.TableGenerator(
 
name="Teacher_GEN",
 
table="GENERATOR_TABLE",
 
pkColumnName="pkkey",
 
valueColumnName="pkvalue",
 
pkColumnValue="Teacher",
 
allocationSize=1
 
)
 
public class Teacher {
 
private int id;
 
private String name;
 
private String title;
 
private String address;
 
private String wifeName;
 
private Date birth;
 
private ZhiCheng zhiCheng;
 
@Id
 
@GeneratedValue(strategy=GenerationType.TABLE,generator="Teacher_GEN")
 
public int getId() {
 
return id;
 
}
 
public void setId(int id) {
 
this.id = id;
 
}
 
@Column(name="_name")
 
public String getName() {
 
return name;
 
}
 
public void setName(String name) {
 
this.name = name;
 
}
 
public String getTitle() {
 
return title;
 
}
 
public void setTitle(String title) {
 
this.title = title;
 
}
 
public String getAddress() {
 
return address;
 
}
 
public void setAddress(String address) {
 
this.address = address;
 
}
 
public String getWifeName() {
 
return wifeName;
 
}
 
public void setWifeName(String wifeName) {
 
this.wifeName = wifeName;
 
}
 
@Temporal(TemporalType.DATE)
 
public Date getBirth() {
 
return birth;
 
}
 
public void setBirth(Date birth) {
 
this.birth = birth;
 
}
 
@Enumerated(EnumType.STRING)
 
public ZhiCheng getZhiCheng() {
 
return zhiCheng;
 
}
 
public void setZhiCheng(ZhiCheng zhiCheng) {
 
this.zhiCheng = zhiCheng;
 
}
 
}

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（2）测试

（3）验证

查看hibernate执行过程中产生的sql语句

Hibernate: select pkvalue from GENERATOR_TABLE where pkkey = 'Teacher' for update

Hibernate: insert into GENERATOR_TABLE(pkkey, pkvalue) values('Teacher', ?)

Hibernate: update GENERATOR_TABLE set pkvalue = ? where pkvalue = ? and pkkey = 'Teacher'

Hibernate: select pkvalue from GENERATOR_TABLE where pkkey = 'Teacher' for update

Hibernate: update GENERATOR_TABLE set pkvalue = ? where pkvalue = ? and pkkey = 'Teacher'

Hibernate: insert into Teacher (address, birth, _name, title, wifeName, zhiCheng, id) values (?, ?, ?, ?, ?, ?, ?)

查看数据表

select * from generator_table;
 
select * from teacher;

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