Hibernate Annotations笔记

注意import javax.xx.Entity ，而不是org.hibernate.xx.Entity。
Descn属性不存在于数据库中，用@Transient 注明
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1,需要: Hibernate库文件,Hibernate Annotations库,ejb3-persstence.jar(Java 持久化API)
sessionFactory=new AnnotationConfiguration().buildSessionFactory();
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2,<bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
     <property name="annotatedClasses">
      <list>
        <value>com.onjava.modelplanes.domain.PlaneType</value>
      </list>
     </property>
 </bean>
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1,@Entity
@Table(name = "teacher_info")
@IdClass(UUIDHexGenerator.class)
public class UserMember implements java.io.Serializable
2,@entity通过getters/setters方法访问，或直接访问他的成员变量。
@Entity(access = AccessType.PROPERTY)
@Entity(access = AccessType.FIELD)
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映射标识符
1,@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private String id;
2,@Id(generate=GeneratorType.SEQUENCE, generator='SEQ_STORE')
3,@Id(generate=GeneratorType.IDENTITY)
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映射属性
1,@Transient
2,@Column(name="PLANE_ID", length=80, nullable=true)
3,@Basic(fetch = FetchType.LAZY)
4,@Serialized 凡标识@Serialized的属性将被序列化
public Country getCountry() { ... }
5,@Lob标识了存储对象可能是个CLOB或者BLOB。
@Lob(type=LobType.CLOB)
public String getFullText(){return fullText;}
@Lob(type = LobType.BLOB)
public byte[] getFullCode() {return fullCode;}
@Version 定义乐观锁机制使用
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关联关系:
一、一对一:
1,@OneToOne(mappedBy = "address")
public User getUser() {
      return user;
}
1、两边都定义了@OneToOne，但都没有定义mappedBy,则user和address表都会生成到对方的外键，双方都是这个关系的拥有者。
2、两边都定义了@OneToOne，如果user定义了mappedBy，则在address表生成到user的外键，address是这个关系的拥有者；如果address定义
了mappedBy，则在user表生成到address的外键，user是这个关系的拥有者。

二、一对多,多对一:
2,@ManyToOne( cascade = {CascadeType.PERSIST, CascadeType.MERGE} )
3,@OneToMany(mappedBy="planeType",cascade=CascadeType.ALL, fetch=FetchType.EAGER)
@OrderBy("name")
public List<ModelPlane> getModelPlanes() {
    return modelPlanes;
}
其中定义mappedBy的是@OneToMany,也就是说One这一方是关系的拥有者。Many一方的表中生成到关联类的外键。

三、@ManyToMany
private Set authors = new HashSet<Author>();
@ManyToMany
public Set<Author> getAuthors(){
return authors;
}

private Set books = new HashSet<Book>();
@ManyToMany(mappedBy="authors")
public Set<Book> getBooks(){
return books;
}
@ManyToMany会生成中间表，具体表名和字段可以通过@AssociationTable来定义，默认的就可以了，同样关系的非拥有者，需要定义mappedBy属性。
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命名查询
你也可以通过注解,利用@NameQueries和@NameQuery注解,如下:
@NamedQueries(
{
@NamedQuery(name="planeType.findAll",query="select p from PlaneType p" ),
@NamedQuery(name="planeType.delete",query="delete from PlaneType where id=:id" )
 }
)
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内嵌对象（组件）
@Embedded({
   @AttributeOverride(name='iso2', column = @Column(name='bornIso2') ),
   @AttributeOverride(name='name', column = @Column(name='bornCountryName') )
         })
    Country bornIn;
    ...
}

@Embeddable(access = AccessType.FIELD)
public class Address implements Serializable {
    String city;
    Country nationality;
}


@Embeddable
public class Country implements Serializable {
    private String iso2;
    private String name;

    public String getIso2() { return iso2; }
    public void setIso2(String iso2) { this.iso2 = iso2; }

    @Column(name='countryName')
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    ...
}
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自定义的主键生成策略
@javax.persistence.GeneratedIdTable(
   name='GEN_TABLE',
  table = @Table(name='GENERATOR_TABLE'),
    pkColumnName = 'key',
      valueColumnName = 'hi'
)

@javax.persistence.TableGenerator(
    name='EMP_GEN',
    tableName='GEN_TABLE',
    pkColumnValue='EMP',
    allocationSize=20
)
@javax.persistence.SequenceGenerator(
    name='SEQ_GEN',
    sequenceName='my_sequence'
)
package org.hibernate.test.metadata;