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• 什么是組件映射
• 代碼

什么是組件映射

多個(gè)實(shí)體類有可能會(huì)有共同的一些屬性，如果把這些屬性單獨(dú)的拿出來，形成一個(gè)類，所有需要的實(shí)體類直接包含它就可以，這樣能簡(jiǎn)化代碼。

1. 組件類不會(huì)形成單獨(dú)的數(shù)據(jù)表結(jié)構(gòu)
2. 組件類的屬性，會(huì)在調(diào)用它的實(shí)體類表結(jié)構(gòu)中被創(chuàng)建

image.png

代碼

User.java

    package entity;
    
    public class User {
        private int id;
        private String name;
        private String phone;
        private UserExtra user_extra;
        public UserExtra getUser_extra() {
            return user_extra;
        }
        public void setUser_extra(UserExtra user_extra) {
            this.user_extra = user_extra;
        }
        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;
        }
        public String getPhone() {
            return phone;
        }
        public void setPhone(String phone) {
            this.phone = phone;
        }
        
        
    }

UserExtra.java

    package entity;
    
    public class UserExtra {
        private int sex;
        private String address;
        public int getSex() {
            return sex;
        }
        public void setSex(int sex) {
            this.sex = sex;
        }
        public String getAddress() {
            return address;
        }
        public void setAddress(String address) {
            this.address = address;
        }   
    }

User.hbm.xml

    <?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 package="entity">
        <class name="entity.User">
            <id name="id">
                <generator class="native"/>
            </id>
            <property name="name"></property>
            <property name="phone"></property>
            <!-- 組件是實(shí)體類的一部分，但是不會(huì)生成獨(dú)立的數(shù)據(jù)表 -->
            <!-- 組件的屬性會(huì)進(jìn)入到User數(shù)據(jù)表中 -->
            <component name="user_extra">
                <property name="sex"></property>
                <property name="address"></property>
            </component>
        </class>    
    </hibernate-mapping>

單元測(cè)試

    package entity;
    
    import org.hibernate.classic.Session;
    
    import junit.framework.TestCase;
    import util.hibernateUtil;
    
    /**
     * 目標(biāo)：測(cè)試組件映射方式
     * 注意：組件是一個(gè)實(shí)體類，其中包含了一些公共的屬性，在做映射關(guān)系的時(shí)候，組件是不生成表的。
     *      但是數(shù)據(jù)表結(jié)構(gòu)中包含組件屬性，也就是User表中包含UserExtra類中的屬性
     * @author arkulo
     *
     */
    
    public class TestDemo extends TestCase {
    
        //數(shù)據(jù)添加  
        public void test1(){
            Session session = null;
            try
            {
                session = hibernateUtil.getSession();
                session.beginTransaction();
                
                User user = new User();
                user.setName("樂迪");
                user.setPhone("18500112233");
                
                UserExtra extra = new UserExtra();
                extra.setSex(1);
                extra.setAddress("大興區(qū)棗園路");
                
                user.setUser_extra(extra);
                
                session.save(user);
                session.getTransaction().commit();
            }catch(Exception e)
            {
                e.printStackTrace();
                session.getTransaction().rollback();
            }finally
            {
                hibernateUtil.closeSession(session);
            }
        }
        
        
    //  讀數(shù)據(jù)，
        public void test2()
        {
            Session session = null;
            try {
                session = hibernateUtil.getSession();
                session.beginTransaction();
                
                User user = (User)session.load(User.class, 1);
                System.out.println("用戶名："+user.getName());
                System.out.println("地址："+user.getUser_extra().getAddress());
                
                session.getTransaction().commit();
            }catch(Exception e){
                e.printStackTrace();
                session.getTransaction().rollback();
            } finally {
                hibernateUtil.closeSession(session);
            }
            
        }
        
    }