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    如图，当多个对象之间有类似的属性的时候，可以将其公用的属性进行抽离：

     拿User和Employee对象举例，此时User和Employee中的公用属性已经被抽离到一个单独的对象“Comtact”当中，但是此时数据表仍然如下：

     由此可见，Component这种映射的方法，在对象模型中“细粒度”，在关系模型中仍然是“粗粒度”。

     代码实现：

    （1）实体

     1.抽取的公共类Contact

public class Contact {private String email;private String address;private String zipCode;private String contactTel;public String getEmail() {return email;}public void setEmail(String email) {this.email = email;}public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}public String getZipCode() {return zipCode;}public void setZipCode(String zipCode) {this.zipCode = zipCode;}public String getContactTel() {return contactTel;}public void setContactTel(String contactTel) {this.contactTel = contactTel;}
}

public class User {private String id;private String name;private Contact userContact;public Contact getUserContact() {return userContact;}public void setUserContact(Contact userContact) {this.userContact = userContact;}public String getId() {return id;}public void setId(String id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}
}

public class Employee {private int id;private String name;private Contact employeeContact;public Contact getEmployeeContact() {return employeeContact;}public void setEmployeeContact(Contact employeeContact) {this.employeeContact = employeeContact;}public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}
}

   （2）.hbm.xml配置文件

<hibernate-mapping><class name="com.bjpowernode.hibernate.Employee" table="t_emplyee"><id name="id"><generator class="native"/></id><property name="name"/><component name="employeeContact"><property name="email"/><property name="address"/><property name="zipCode"/><property name="contactTel"/></component></class><class name="com.bjpowernode.hibernate.User" table="t_user"><id name="id"><generator class="native"/></id><property name="name"/><component name="employeeContact"><property name="email"/><property name="address"/><property name="zipCode"/><property name="contactTel"/></component></class>
</hibernate-mapping> 

     由此可见，在该hbm.xml当中，主键生成策略为"native"，正常的name属性之后，加入<component>关联属性，子标签中加入<email><address>等子属性。

   （3）存储、加载测试

public void testSave1(){Session session = null;try{session = HibernateUtils.getSession();session.beginTransaction();User user = new User();user.setName("张三");Contact userContact = new Contact();userContact.setAddress("address");userContact.setContactTel("contactTel");userContact.setEmail("email");userContact.setZipCode("zipCode");user.setUserContact(userContact);session.save(user);session.getTransaction().commit();}catch(Exception e){e.printStackTrace();}finally{HibernateUtils.closeSession(session);}
}

    同理，加载方法如下：

public void testLoad1(){Session session = null;try{session = HibernateUtils.getSession();session.beginTransaction();User user = (User)session.load(User.class, 1);System.out.println(user.getName());System.out.println(user.getUserContact().getAddress());session.save(user);session.getTransaction().commit();}catch(Exception e){e.printStackTrace();}finally{HibernateUtils.closeSession(session);}
}

   总结：

   采用Component的好处在于，实现对象模型的细粒度划分，复用率更高，层次更加分明。