 从 hbm.xml 到 Annotations 下面让我们先看一个通常用 hbm.xml 映射文档的例子. 有3个类 .HibernateUtil.java 也就是 Hibernate文档中推荐的工具类,Person.java, Test.java 测试用的类.都在test.hibernate 包中. 每个类的代码如下: HibernateUtil: 01 package test.hibernate; 02 03 import org.hibernate.HibernateException; 04 import org.hibernate.Session; 05 import org.hibernate.SessionFactory; 06 import org.hibernate.cfg.Configuration; 07 08 public class HibernateUtil { 09 public static final SessionFactory sessionFactory; 10 11 static { 12 try { 13 sessionFactory = new Configuration() 14 .configure() 15 .buildSessionFactory(); 16 } catch (HibernateException e) { 17 // TODO Auto-generated catch block 18 19 e.printStackTrace(); 20 throw new ExceptionInInitializerError(e); 21 } 22 } 23 24 public static final ThreadLocal 25 26 public static Session currentSession() throws HibernateException { 27 Session s = session.get(); 28 29 if(s == null) { 30 s = sessionFactory.openSession(); 31 session.set(s); 32 } 33 34 return s; 35 } 36 37 public static void closeSession() throws HibernateException { 38 Session s = session.get(); 39 if(s != null) { 40 s.close(); 41 } 42 session.set(null); 43 } 44 } Person: 01 package test.hibernate; 02 03 import java.util.LinkedList; 04 import java.util.List; 05 06 /** 07 * 08 */ 09 10 @SuppressWarnings("serial") 11 public class Person implements java.io.Serializable { 12 13 // Fields 14 15 private Integer id; 16 17 private String name; 18 19 private String sex; 20 21 private Integer age; 22 23 private List list = new LinkedList(); 24 25 // Collection accessors 26 27 public List getList() { 28 return list; 29 } 30 31 public void setList(List list) { 32 this.list = list; 33 } 34 35 /** default constructor */ 36 public Person() { 37 } 38 39 /** constructor with id */ 40 public Person(Integer id) { 41 this.id = id; 42 } 43 44 // Property accessors 45 46 public Integer getId() { 47 return this.id; 48 } 49 50 public void setId(Integer id) { 51 this.id = id; 52 } 53 54 public String getName() { 55 return this.name; 56 } 57 58 public void setName(String name) { 59 this.name = name; 60 } 61 62 public String getSex() { 63 return this.sex; 64 } 65 66 public void setSex(String sex) { 67 this.sex = sex; 68 } 69 70 public Integer getAge() { 71 return this.age; 72 } 73 74 public void setAge(Integer age) { 75 this.age = age; 76 } 77 78 } Test: 01 /* 02 * Created on 03 * @author 04 */ 05 package test.hibernate; 06 07 import java.sql.SQLException; 08 09 import org.hibernate.FlushMode; 10 import org.hibernate.HibernateException; 11 import org.hibernate.Session; 12 import org.hibernate.Transaction; 13 14 public class Test { 15 16 public static void main(String [] args) { 17 Session s = HibernateUtil.currentSession(); 18 19 Transaction tx = s.beginTransaction(); 20 21 // Person p = (Person) s.load(Person.class, 1); 22 // System.out.println(p.getName()); 23 Person p = new Person(); 24 25 p.setAge(19); 26 p.setName("icerain"); 27 p.setSex("male"); 28 s.save(p); 29 s.flush(); 30 /* 31 Person p2 = (Person) s.get(Person.class, new Integer(1)); 32 System.out.println(p2.getName()); 33 p2.setName("ice.."); 34 s.saveOrUpdate(p2); 35 s.flush(); 36 Person p3 = (Person) s.get(Person.class, new Integer(2)); 37 System.out.println(p3.getName()); 38 s.delete(p3); 39 */ 40 41 tx.commit(); 42 try { 43 System.out.println(p.getName()); 44 } catch (Exception e) { 45 // TODO Auto-generated catch block 46 e.printStackTrace(); 47 } 48 49 HibernateUtil.closeSession(); 50 } 51 } hibernate.cfg.xml 配置文档如下,利用mysql 数据库. 其中 配置了 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 文档如下: 下面让我们看看利用 Hibernate Annotations 怎样做,只要三个类 不再需要 hbm.xml配置文档: 还要把用到的两个jar文档 放入的类路径中. 具体怎样做,请参考 Hibernate Annotations 中文文档 http://hibernate.6644.net 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.annotation 包中. 每个类的代码如下: HibernateUtil 01 package test.hibernate.annotation; 02 03 import org.hibernate.HibernateException; 04 import org.hibernate.Session; 05 import org.hibernate.SessionFactory; 06 import org.hibernate.cfg.AnnotationConfiguration; 07 import org.hibernate.cfg.Configuration; 08 09 public class HibernateUtil { 10 public static final SessionFactory sessionFactory; 11 12 static { 13 try { 14 sessionFactory = new AnnotationConfiguration() //注意: 建立 SessionFactory于前面的不同 15 .addPackage("test.hibernate.annotation") 16 .addAnnotatedClass(Person.class) 17 18 .configure() 19 .buildSessionFactory(); 20 //new Configuration().configure().buildSessionFactory(); 21 } catch (HibernateException e) { 22 // TODO Auto-generated catch block 23 24 e.printStackTrace(); 25 throw new ExceptionInInitializerError(e); 26 } 27 } 28 29 public static final ThreadLocal 30 31 public static Session currentSession() throws HibernateException { 32 Session s = session.get(); 33 34 if(s == null) { 35 s = sessionFactory.openSession(); 36 session.set(s); 37 } 38 39 return s; 40 } 41 42 public static void closeSession() throws HibernateException { 43 Session s = session.get(); 44 if(s != null) { 45 s.close(); 46 } 47 session.set(null); 48 } 49 } Person: 01 package test.hibernate.annotation; 02 03 import java.util.LinkedList; 04 import java.util.List; 05 06 import javax.persistence.AccessType; 07 import javax.persistence.Basic; 08 import javax.persistence.Entity; 09 import javax.persistence.GeneratorType; 10 import javax.persistence.Id; 11 import javax.persistence.OneToMany; 12 import javax.persistence.Table; 13 import javax.persistence.Transient; 14 15 /** 16 * 17 */ 18 19 @SuppressWarnings("serial") 20 @Entity(access = AccessType.PROPERTY) //定义该类为实体类 21 @Table //映射表 22 public class Person implements java.io.Serializable { 23 24 // Fields 25 26 private Integer id; 27 28 private String name; 29 30 private String sex; 31 32 private Integer age; 33 34 private List list = new LinkedList(); 35 36 // Constructors 37 /** default constructor */ 38 public Person() { 39 } 40 41 /** constructor with id */ 42 public Person(Integer id) { 43 this.id = id; 44 } 45 46 // Property accessors 47 @Id 48 public Integer getId() { 49 return this.id; 50 } 51 52 public void setId(Integer id) { 53 this.id = id; 54 } 55 56 @Basic 57 public String getName() { 58 return this.name; 59 } 60 61 public void setName(String name) { 62 this.name = name; 63 } 64 65 @Basic 66 public String getSex() { 67 return this.sex; 68 } 69 70 public void setSex(String sex) { 71 this.sex = sex; 72 } 73 74 @Basic 75 public Integer getAge() { 76 return this.age; 77 } 78 79 public void setAge(Integer age) { 80 this.age = age; 81 } 82 @Transient //由于本例不打算演示集合映射 任何声明该属性为 Transient 83 public List getList() { 84 return list; 85 } 86 87 public void setList(List list) { 88 this.list = list; 89 } 90 91 } 注意该实体类中的属性都使用了默认值. Test.java 代码同上 无需了 hbm.xml 映射文档, 是不是简单了一些 .给人认为简化了一些不是主要目的.主要是能够了解一下 EJB3 的持久化机制 ,提高一下研发效率才是重要的. 好了 .本例就完了 . 感觉怎么样了 .欢迎您来批批. PS: 生成的数据库表 和 程式执行后的 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) |
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