[轉載]嘗試hibernate annotations

最近開始嘗試hibernate annotations，終於成功的將手上一個小應用轉爲annotations

1、spring orm support
與原來使用LocalSessionFactoryBean相比，變動不大（AnnotationSessionFactoryBean本來就是從LocalSessionFactoryBean類繼承過來的嘛）

<!--<br><br>Code highlighting produced by Actipro CodeHighlighter (freeware)<br>http://www.CodeHighlighter.com/<br><br>--> 1 <bean
2 id="sessionFactory"
3 class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean"
4 parent="AbstractSessionFactory">
5 <property name="annotatedClasses">
6 <list>
7 <value>xxx.xxx.xxx.domain.Accountvalue>
8 list>
9 property>
10 bean>
11 <bean
12 id="AbstractSessionFactory"
13 class="org.springframework.orm.hibernate3.LocalSessionFactoryBean"
14 abstract="true">
15 <property
16 name="dataSource"
17 ref="DataSource" />
18 <property name="hibernateProperties">
19 <props>
20 <prop key="hibernate.dialect">${hibernate.dialect}prop>
21 <prop key="hibernate.show_sql">${hibernate.show_sql}prop>
22 <prop key="hibernate.hbm2ddl.auto">${hibernate.hbm2ddl.auto}prop>
23 <prop key="hibernate.cache.use_query_cache">${hibernate.cache.use_query_cache}prop>
24 <prop key="hibernate.cache.provider_class">${hibernate.cache.provider_class}prop>
25 props>
26 property>
27 <property
28 name="lobHandler"
29 ref="DefaultLobHandler" />
30 bean>
2、id的配置
非常簡單，在id的getter上面加個“@Id”就可以了。此時採用的id策略是javax.persistence.GenerationType.AUTO，也可以再加上“@GeneratedValue(generator =GenerationType.IDENTITY|GenerationType.SEQUENCE|GenerationType.TABLE)”換成其它策略。
我的應用採用的是hibernate的uuid策略，就不得不在這兒使用hibernate的擴展了

<!--<br><br>Code highlighting produced by Actipro CodeHighlighter (freeware)<br>http://www.CodeHighlighter.com/<br><br>--> @Id
@Column(length = 32)
@GeneratedValue(generator = "system-uuid")
@GenericGenerator(name = "system-uuid", strategy = "uuid")

3、級聯策略
在ejb3-persistence.jar中只定義了ALL、MERGE、PERSIST、REFRESH、REMOVE，比較噁心的就是，刪除對象的時候，並不會級聯刪除關聯對象，而是用update xx set parent_id=null where parent_id=?這類語句把關係幹掉了事。不得已，在這兒用了hibernate的DELETE_ORPHAN。

<!--<br><br>Code highlighting produced by Actipro CodeHighlighter (freeware)<br>http://www.CodeHighlighter.com/<br><br>--> @OneToMany(targetEntity = Attachment.class)
@Cascade(value = {org.hibernate.annotations.CascadeType.DELETE_ORPHAN,
org.hibernate.annotations.CascadeType.ALL})
@JoinColumn(name = "info_id")
4、CACHE
ejb3-persistence.jar裏面沒有找到cache的配置，繼續請出hibernate來幹活

<!--<br><br>Code highlighting produced by Actipro CodeHighlighter (freeware)<br>http://www.CodeHighlighter.com/<br><br>-->import org.hibernate.annotations.Cache;
import org.hibernate.annotations.CacheConcurrencyStrategy;

@Entity
@Table(name = "T_INFO")
@Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE)
5、自定義字段類型
我的POJO中有一個private String content;的屬性，按ejb3配成@Lob後，被處理成了text類型，text 64k的存儲容量還是比較可憐了。

<!--<br><br>Code highlighting produced by Actipro CodeHighlighter (freeware)<br>http://www.CodeHighlighter.com/<br><br>--> @Lob
@Column(columnDefinition = "LongText")