整合Spring+Hibernate时，主键策略是assigned插入不进数据，也不报任何错！

Question

在save()前打印了一下实体类，save()后也打印了一下实体类，都是有值，但是数据库里就是插入不进数据，我把Student.hbm.xml中的assigned改成native，就能插入进数据。。。

Dao层

 public class UserDaoImpl implements UserDao {

    private SessionFactory sessionFactory;

    @Autowired
    public void setSessionFactoryOverride(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }

    public void addStudent(Student student) {
        System.out.println(sessionFactory);
        System.out.println("添加前:" + student);
        sessionFactory.getCurrentSession().save(student);
    }
}

Student.hbm.xml

<hibernate-mapping>  
    <class name="com.zlm.entity.Student" table="student">    
        <id name="studentId" type="java.lang.Integer" >
            <column name="studentId" />
            <generator class="assigned" />
        </id>
        <property name="password" type="java.lang.String">  
            <column name="password" />  
        </property>  
        <property name="identify" type="java.lang.Integer">  
            <column name="identify" />  
        </property>  
    </class>  
</hibernate-mapping> 

实体类就是
private int studentId;
get
set

applicationContext.xml

<beans>
    <context:component-scan base-package="com.zlm"
        use-default-filters="false" />
    <context:property-placeholder location="classpath:config/db.properties" />
    <bean id="dataSource"
        class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="${jdbc.driverClass}"></property>
        <property name="url" value="${jdbc.jdbcUrl}"></property>
        <property name="username" value="${jdbc.user}"></property>
        <property name="password" value="${jdbc.password}"></property>
    </bean>
    <bean id="sessionFactory"
        class="org.springframework.orm.hibernate5.LocalSessionFactoryBean">
        <property name="dataSource" ref="dataSource" />
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">org.hibernate.dialect.MySQL5InnoDBDialect </prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.format_sql">true</prop>
                <prop key="hibernate.hbm2ddl.auto">update</prop>
                <prop key="hibernate.temp.use_jdbc_metadata_defaults">false</prop>

            </props>
        </property>
        <property name="mappingResources">
            <list>
                <value>com/zlm/entity/Student.hbm.xml</value>
            </list>
        </property>

    </bean>
    <bean id="transactionManager"
        class="org.springframework.orm.hibernate5.HibernateTransactionManager">
        <property name="sessionFactory" ref="sessionFactory"></property>
    </bean>
</beans>

Answer 1