来源：http://www.360doc.com/content/06/0425/12/5136_104878.shtml
-- 从 hbm.xml 到 Annotations
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作者：icess(作者的blog:http://blog.matrix.org.cn/page/icess)
关键字：Hibernate Validator
下面让我们先看一个通常用 hbm.xml 映射文件的例子. 有3个类 .HibernateUtil.java 也就是 Hibernate文档中推荐的工具类,Person.java 一个持久化的类, Test.java 测试用的类.都在test.hibernate 包中. 每个类的代码如下:
HIbernateUtil工具类：
package test.hibernate;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateUtil {
public static final SessionFactory sessionFactory;
static {
try {
sessionFactory = new Configuration()
.configure()
.buildSessionFactory();
} catch (HibernateException e) {
// TODO Auto-generated catch block
e.printStackTrace();
throw new ExceptionInInitializerError(e);
}
}
public static final ThreadLocal<Session> session = new ThreadLocal<Session>();
public static Session currentSession() throws HibernateException {
Session s = session.get();
if(s == null) {
s = sessionFactory.openSession();
session.set(s);
}
return s;
}
public static void closeSession() throws HibernateException {
Session s = session.get();
if(s != null) {
s.close();
}
session.set(null);
}
}
用户实体类：Person
package test.hibernate;
import java.util.LinkedList;
import java.util.List;
/**
*
*/
@SuppressWarnings("serial")
public class Person implements java.io.Serializable {
// Fields
private Integer id;
private String name;
private String sex;
private Integer age;
private List list = new LinkedList();
// Collection accessors
public List getList() {
return list;
}
public void setList(List list) {
this.list = list;
}
/** default constructor */
public Person() {
}
/** constructor with id */
public Person(Integer id) {
this.id = id;
}
// Property accessors
public Integer getId() {
return this.id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
public String getSex() {
return this.sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public Integer getAge() {
return this.age;
}
public void setAge(Integer age) {
this.age = age;
}
}
/*
* Created on
* @author
*/
package test.hibernate;
import java.sql.SQLException;
import org.hibernate.FlushMode;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.Transaction;
public class Test {
public static void main(String [] args) {
Session s = HibernateUtil.currentSession();
Transaction tx = s.beginTransaction();
// Person p = (Person) s.load(Person.class, 1);
// System.out.println(p.getName());
Person p = new Person();
p.setAge(19);
p.setName("icerain");
p.setSex("male");
s.save(p);
s.flush();
/*
Person p2 = (Person) s.get(Person.class, new Integer(1));
System.out.println(p2.getName());
p2.setName("ice..");
s.saveOrUpdate(p2);
s.flush();
Person p3 = (Person) s.get(Person.class, new Integer(2));
System.out.println(p3.getName());
s.delete(p3);
*/
tx.commit();
try {
System.out.println(p.getName());
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
HibernateUtil.closeSession();
}
}
hibernate.cfg.xml 配置文件如下,利用mysql 数据库.
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <property name="hibernate.connection.driver_class">org.gjt.mm.mysql.Driver</property> <property name="hibernate.connection.password">你的数据库密码</property> <property name="hibernate.connection.url">jdbc:mysql://localhost/数据库名</property> <property name="hibernate.connection.username">用户名</property> <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property> <property name="show_sql">true</property> <property name="hibernate.transaction.factory_class">org.hibernate.transaction.JDBCTransactionFactory</property> <property name="hibernate.transaction.auto_close_session">false</property> <property name="hibernate.hbm2ddl.auto">update</property> <mapping resource="test/hibernate/annotation/Person.hbm.xml"/> </session-factory> </hibernate-configuration>
其中 配置了<property name="hibernate.hbm2ddl.auto">update</property>属性 自动导入数据库ddl.生产的ddl sql语句如下
create table person (id integer not null auto_increment, name varchar(255), sex varchar(255), age integer, person integer, primary key (id)) alter table person add index FKC4E39B5511C4A5C2 (person), add constraint FKC4E39B5511C4A5C2 foreign key (person) references person (id)
而Person.hbm.xml 文件如下:
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name="test.hibernate.Person" table="person"> <id name="id" type="integer"> <column name="id" /> <generator class="native"></generator> </id> <property name="name" type="string"> <column name="name" /> </property> <property name="sex" type="string"> <column name="sex" /> </property> <property name="age" type="integer"> <column name="age" /> </property> <bag name="list" cascade="all"> <key column="person"></key> <one-to-many class="test.hibernate.Person"/> </bag> </class> </hibernate-mapping>
下面让我们看看利用 Hibernate Annotations 如何做,只要三个类 不再需要 hbm.xml配置文件:还要把用到的两个jar文件 放入的类路径中. 具体如何做,请参考 Hibernate Annotations 中文文档http://hb.6644.netHibernateUtil.java 也就是 Hibernate文档中推荐的工具类,Person.java 一个持久化的类, Test.java 测试用的类.都在test.hibernate.annotation 包中. 每个类的代码如下:
package test.hibernate.annotation;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.cfg.Configuration;
public class HibernateUtil {
public static final SessionFactory sessionFactory;
static {
try {
sessionFactory = new AnnotationConfiguration() //注意: 建立 SessionFactory于前面的不同
.addPackage("test.hibernate.annotation")
.addAnnotatedClass(Person.class)
.configure()
.buildSessionFactory();
//new Configuration().configure().buildSessionFactory();
} catch (HibernateException e) {
// TODO Auto-generated catch block
e.printStackTrace();
throw new ExceptionInInitializerError(e);
}
}
public static final ThreadLocal<Session> session = new ThreadLocal<Session>();
public static Session currentSession() throws HibernateException {
Session s = session.get();
if(s == null) {
s = sessionFactory.openSession();
session.set(s);
}
return s;
}
public static void closeSession() throws HibernateException {
Session s = session.get();
if(s != null) {
s.close();
}
session.set(null);
}
}
package test.hibernate.annotation;
import java.util.LinkedList;
import java.util.List;
import javax.persistence.AccessType;
import javax.persistence.Basic;
import javax.persistence.Entity;
import javax.persistence.GeneratorType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import javax.persistence.Transient;
/**
*
*/
@SuppressWarnings("serial")
@Entity(access = AccessType.PROPERTY) //定义该类为实体类
@Table //映射表
public class Person implements java.io.Serializable {
// Fields
private Integer id;
private String name;
private String sex;
private Integer age;
private List list = new LinkedList();
// Constructors
/** default constructor */
public Person() {
}
/** constructor with id */
public Person(Integer id) {
this.id = id;
}
// Property accessors
@Id
public Integer getId() {
return this.id;
}
public void setId(Integer id) {
this.id = id;
}
@Basic
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
@Basic
public String getSex() {
return this.sex;
}
public void setSex(String sex) {
this.sex = sex;
}
@Basic
public Integer getAge() {
return this.age;
}
public void setAge(Integer age) {
this.age = age;
}
@Transient //由于本例不打算演示集合映射 所有声明该属性为 Transient
public List getList() {
return list;
}
public void setList(List list) {
this.list = list;
}
}
注意该实体类中的属性都使用了默认值.Test.java 代码同上不需要了 hbm.xml 映射文件, 是不是简单了一些 .给人认为简化了一些不是主要目的.主要是可以了解一下 EJB3 的持久化机制 ,提高一下开发效率才是重要的.好了 .本例就完了 . 感觉怎么样了 .欢迎你来批批.PS:生成的数据库表 和 程序执行后的 数据库情况如下：
mysql> describe person;
+--------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(255) | YES | | NULL | |
| sex | varchar(255) | YES | | NULL | |
| age | int(11) | YES | | NULL | |
| person | int(11) | YES | MUL | NULL | |
+--------+--------------+------+-----+---------+----------------+
5 rows in set (0.00 sec)
mysql> select * from person;
+----+---------+------+------+--------+
| id | name | sex | age | person |
+----+---------+------+------+--------+
| 1 | icerain | male | 19 | NULL |
+----+---------+------+------+--------+
1 row in set (0.03 sec)