今天有時間大體看了一下Hibernate Annotations,決定放棄xdoclet生成hbm的想法，開始學習annotation.
首先大體的來看一下：
一：Class Level:
1:通過@Entity聲明當前pojo為實體Bean
2:通過@Table定義對應數據庫表的屬性
name：表名，默認實體類名
uniqueConstraints：定義表的唯一性約束
例：定義表名為tb_user,并且用戶名唯一，不能重復
@Entity
@Table(
name = "tb_user",
uniqueConstraints =
{@UniqueConstraint(columnNames = "userName")}
)
public class User implements Serializable {
private Integer id;
private String userName;
}二：Method Level:
@Basic
@Transient
@Column
所有非static非transient都會被持久化，也就是說所有加@Transient是不會被保存到數據庫中的，所有沒有加注的默認為@Basic,通過Column我們可以更一步的定義列名，是否為空，長度，是否可更新等等屬性值，
例：
@Column(name = "userName", nullable = false, length = 80, unique = true)
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
@Transient
public String getPassword() {
return password;
} 默認的列名就是屬性名，上面的name="userName"只是演示而已。
password加注為@Transient，所以通過SchemaExport導入Schema，查看表結構是沒有這個字段的。
@Temporal
日期類型，分三種，Time,Date,Timestamp
例：
@Temporal(TemporalType.TIMESTAMP)
public Date getBirthday() {
return birthday;
} @Lob
1:所有的Clob，
Character，char，String都會被轉為Clob
2:所有的Blob，Byte[]，byte[]，serializable都會被轉為Blob
例：
@Lob
public Clob getResume() {
return resume;
}
@Lob
public Blob getImage() {
return image;
}
@Id
就是標識了，暫時還沒有詳讀文檔，看了一下test
最簡單方式如下：
@Id
@GeneratedValue
public String getId() {
return id;
} 我看了一下mysql生成的sql
id integer not null auto_increment,
primary key (id), 應該是hibernate根據數據庫類型自動選擇的(說了一句廢話
)，我猜是生成方式native
當然我們可以根據我們需要選擇其他的生成方式，例如常用的uuid
@Id
@GeneratedValue(generator = "system-uuid")
@GenericGenerator(name = "system-uuid", strategy = "uuid")
public Integer getId() {
return id;
} @Version
樂觀鎖
三：跑起來
和Hibernate官方網站一樣，來個HibernateUtil
/**
* @author martin
*/
public class HibernateUtil {
private static final SessionFactory sessionFactory;
static {
AnnotationConfiguration cfg =
new AnnotationConfiguration().addAnnotatedClass(User.class);
new SchemaExport(cfg).execute(true, true, false, true);
sessionFactory = cfg.buildSessionFactory();
}
public static Session getSession() {
return sessionFactory.openSession();
}
}
注意這里的
new AnnotationConfiguration()！
Test:
/**
* @author martin
*/
public class HibernateUtilTest extends TestCase {
public void testAddUser() {
User user = new User();
user.setUserName("martin");
save(user);
assertNotNull(user.getId());
}
public void testUpdateUser() {
Session session = HibernateUtil.getSession();
Query query =
session.createQuery("from User as user where user.userName=:name");
query.setParameter("name", "martin");
List list = query.list();
session.close();
assertEquals(1, list.size());
User user = (User) list.get(0);
user.setUserName("martin xus");
save(user);
assertEquals(new Integer(1), user.getVersion());
}
private void save(User user) {
Session session = HibernateUtil.getSession();
Transaction tx = session.beginTransaction();
session.saveOrUpdate(user);
session.flush();
tx.commit();
session.close();
}
}
創建的表結構為：
create table tb_user (
id varchar(32) not null,
birthday datetime,
resume text,
image blob,
optlock integer,
password varchar(255),
userName varchar(80) not null unique,
primary key (id),
unique (userName)
) 完整User代碼(省掉了所有屬性的setter)：
import org.hibernate.annotations.GenericGenerator;
import javax.persistence.*;
import java.io.Serializable;
import java.util.Date;
import java.sql.Clob;
import java.sql.Blob;
/** *//**
* @author martin
*/
@Entity
@Table(
name = "tb_user",
uniqueConstraints =
{@UniqueConstraint(columnNames = "userName")}
)
public class User implements Serializable {
private String id;
private String userName;
private String password;
private Date birthday;
private Clob resume;
private Blob image;
private Integer version;
@Id
@GeneratedValue(generator = "system-uuid")
@GenericGenerator(name = "system-uuid", strategy = "uuid")
@Column(length = 32)
public String getId() {
return id;
}
@Column(nullable = false, length = 80, unique = true)
public String getUserName() {
return userName;
}
public String getPassword() {
return password;
}
@Temporal(TemporalType.TIMESTAMP)
public Date getBirthday() {
return birthday;
}
@Version
@Column(name = "optlock")
public Integer getVersion() {
return version;
}
@Lob
public Clob getResume() {
return resume;
}
@Lob
public Blob getImage() {
return image;
}
//setter
} 四：next,明天的學習計劃.
參考
Hibernate Annotations Refrence