Java Hibernate:基于实体类自动创建/更新db表
我有以下实体类(在Groovy中): 和my persistence.xml:Java Hibernate:基于实体类自动创建/更新db表,java,mysql,hibernate,jpa,groovy,Java,Mysql,Hibernate,Jpa,Groovy,我有以下实体类(在Groovy中): 和my persistence.xml: <?xml version="1.0" encoding="UTF-8"?> <persistence xmlns="http://java.sun.com/xml/ns/persistence" version="1.0"> <persistence-unit name="NewPersistenceUnit"> <provider>org.h
<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="1.0">
<persistence-unit name="NewPersistenceUnit">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<properties>
<property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/Icarus"/>
<property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
<property name="hibernate.connection.username" value="root"/>
<property name="hibernate.connection.password" value=""/>
<property name="hibernate.archive.autodetection" value="class"/>
<property name="hibernate.show_sql" value="true"/>
<property name="hibernate.format_sql" value="true"/>
<property name="hbm2ddl.auto" value="create"/>
</properties>
<class>net.interaxia.icarus.data.models.ServerNode</class>
</persistence-unit>
</persistence>
数据库Icarus存在,但当前没有表。我希望Hibernate根据实体类自动创建和/或更新表。如何实现这一点?您可以尝试将persistence.xml中的这一行从
<property name="hbm2ddl.auto" value="create"/>
致:
这是为了维护模式,以跟踪您每次运行应用程序时对模型所做的任何更改
这是从那里得到的,我不知道把
hibernate
放在前面是否会有所不同
建议它应该是hibernate.hbm2ddl.auto
值create
将在sessionFactory创建时创建表,并保持它们不变
值create drop
将创建表,然后在关闭sessionFactory时删除它们
也许您应该显式地设置注释
希望这能有所帮助。有时,根据配置的设置,属性标签的长格式和短格式也会有所不同 e、 g.如果您有类似于:
<property name="hibernate.hbm2ddl.auto" value="create"/>
尝试将其更改为:
<property name="hibernate.hbm2ddl.auto">create</property>
创建
有一个非常重要的细节,可以阻止hibernate生成表(假设您已经设置了hibernate.hbm2ddl.auto
)。您还需要@Table
注释
@Entity
@Table(name = "test_entity")
public class TestEntity {
}
在我的情况下,它已经帮助了我至少3次-仍然记不起来;)
PS.阅读hibernate文档-在大多数情况下,您可能不想将
hibernate.hbm2ddl.auto
设置为create drop
,因为它会在停止应用程序后删除您的表。在applicationContext.xml文件中:
<bean id="entityManagerFactoryBean" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource" />
<!-- This makes /META-INF/persistence.xml is no longer necessary -->
<property name="packagesToScan" value="com.howtodoinjava.demo.model" />
<!-- JpaVendorAdapter implementation for Hibernate EntityManager.
Exposes Hibernate's persistence provider and EntityManager extension interface -->
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter" />
</property>
<property name="jpaProperties">
<props>
<prop key="hibernate.hbm2ddl.auto">update</prop>
<prop key="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</prop>
</props>
</property>
</bean>
更新
org.hibernate.dialogue.mysql5dialogue
在我的案例中,如果没有下面列出的last属性,表不是第一次创建的:
<properties>
<property name="hibernate.archive.autodetection" value="class"/>
<property name="hibernate.show_sql" value="true"/>
<property name="hibernate.format_sql" value="true"/>
<property name="hbm2ddl.auto" value="create-drop"/>
<!-- without below table was not created -->
<property name="javax.persistence.schema-generation.database.action" value="drop-and-create" />
</properties>
使用Wildfly的内存H2数据库为了支持@Thrinkor的答案,我将扩展我的答案,不仅对实体使用@Table(name=“Table_name”)注释,而且实体类的每个子变量都应该用@Column(name=“col_name”)注释。这将导致对表的无缝更新
对于那些正在寻找基于Java类的hibernate配置的人,该规则也适用于基于Java的配置(NewHibernateUtil)。希望它能帮助其他人。这是hbm2dll.auto开头缺少的“hibernate”。谢谢我刚拆下那条线,它就不会掉桌子了。希望这有帮助!如何使hibernate仅在表不存在时创建表?
@Entity
@Table(name = "test_entity")
public class TestEntity {
}
<bean id="entityManagerFactoryBean" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource" />
<!-- This makes /META-INF/persistence.xml is no longer necessary -->
<property name="packagesToScan" value="com.howtodoinjava.demo.model" />
<!-- JpaVendorAdapter implementation for Hibernate EntityManager.
Exposes Hibernate's persistence provider and EntityManager extension interface -->
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter" />
</property>
<property name="jpaProperties">
<props>
<prop key="hibernate.hbm2ddl.auto">update</prop>
<prop key="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</prop>
</props>
</property>
</bean>
<properties>
<property name="hibernate.archive.autodetection" value="class"/>
<property name="hibernate.show_sql" value="true"/>
<property name="hibernate.format_sql" value="true"/>
<property name="hbm2ddl.auto" value="create-drop"/>
<!-- without below table was not created -->
<property name="javax.persistence.schema-generation.database.action" value="drop-and-create" />
</properties>