Hibernate id generation strategy|The difference between native, assigned and UUID

Hibernate id generation strategy and the difference between native, assigned and UUID
1：the assigned primary key strategy needs to manual set up the ID  when the data is inserted, because it does not automatically generate ID.

1. <?xml version="1.0"?>
2. <!DOCTYPE hibernate-mapping PUBLIC 
3.    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
4.    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
5. <hibernate-mapping>
6.    <class name="com.baidu.entity.Student" table="student">
7.       <id name="id" column="id">
8.           <generator class="assigned"></generator>
9.       </id>
10.       <property name="name" column="name"></property>
11.       <property name="gender" column="gender"></property>
12.       <property name="age" column="age"></property>
13.    </class>
14. </hibernate-mapping>

2：the native primary key strategy will automatically generate ID when the data is inserted, the entity class attribute is Number type.

1. <id name="id" column="id">
2.   <generator class="native"></generator>
3. </id>

2：The uuid.hex primary key strategy automatically generates a 16 base UUID primary key, and the ID is not required when the data is inserted into the MySQL database, the entity class attribute is String type.

1. <id name="id" type="java.lang.String">
2. <column name="id" length="32" />
3. <generator class="uuid.hex" />
4. </id>