love fish大鵬一曰同風(fēng)起，扶搖直上九萬里

                
    // 獲得默認(rèn)當(dāng)前的EntityManagerFactory                
    final EntityManagerFactory emf = Persistence.createEntityManagerFactory();
    final EntityManager entityManager = emf.createEntityManager();    
                
            

                
<entity-manager>
    <name>myEntityManager</name>
    <provider>com.redsoft.ejb3.PersistenceProviderImpl</provider>
    <class>com.redsoft.samples.HelloEntityBean</class>
    <properties>
        <property name="ConnectionDriverName" value="com.mysql.jdbc.Driver"/>
        <property name="ConnectionURL" value="jdbc:mysql://localhost/EJB3Test"/>
        <property name="ConnectionUserName" value="ejb3"/>
        <property name="ConnectionPassword" value="ejb3"/>
        <property name="RetainValues" value="true"/>
        <property name="RestoreValues" value="false"/>
        <property name="IgnoreCache" value="false"/>
        <property name="NontransactionalRead" value="true"/>
        <property name="NontransactionalWrite" value="false"/>
        <property name="Multithreaded" value="false"/>
        <property name="Liberator.option.action" value="create"/>
        <property name="Liberator.option.cache" value="com.redsoft.jdo.enterprise.OscacheAdapter"/>
        <property name="Liberator.option.JMXEnabled" value="false"/>
        <property name="Liberator.option.NamingPort" value="3012"/>
        <property name="Liberator.option.JMXPort" value="3011"/>
        <property name="Liberator.option.JDBC.scrollable" value="false"/>
        <property name="Liberator.option.JDBC.fetchSize" value="500"/>
        <property name="cache.algorithm" value="LRUCache"/>
        <property name="cache.capacity" value="5000"/>
        <property name="log4j.logger.com.redsoft" value="FATAL"/>
    </properties>
</entity-manager>   
                
            

                
    final EntityManagerFactory emf = Persistence.createEntityManagerFactory();
    final EntityManager entityManager = emf.createEntityManager();

    final HelloEntityBean hello = new HelloEntityBean( 1, "foo" );
    EntityTransaction trans = entityManager.getTransaction();
    trans.begin();
    
    // 持久化hello,在此操作之前hello的狀態(tài)為new
    entityManager.persist( hello );
    
    // 這時(shí)hello的狀態(tài)變?yōu)閙anaged
    
    trans.commit();

    entityManager.close();
    
    // 這時(shí)hellow的狀態(tài)變?yōu)閐etached.
    
                 
            

                
    public class Father{
        @Id
        int id
        
        String name;
        
        // OneToOne沒有配置cascade屬性，因此默認(rèn)不會(huì)使用Persistence by reachablity
        @OneToOne
        Son mySon
        
        public Father( int id, String name, Son mySon ){
            this.id = id;
            this.name = name;
            this.mySon = mySon;
        }
    }
                  

                
    final EntityManager manager = emf.createEntityManager();
    manager.getTransaction().begin;
    
    Son mySon = new Son();
    Father = new Father( 1, "father" mySon );
    
    // 保存Father
    manager.persist( father );
    
    // 由于OneToOne關(guān)系中沒有配置casacade屬性，father 關(guān)聯(lián)的mySon不會(huì)被自動(dòng)保存，需要分別保存
    manager.persist( mySon );
    manager.getTransaction().commit();
    manager.close();
                 

                
    public class Father{
        @Id
        int id
        
        String name;
        
        // OneToOne配置cascade=CascadeType.ALL,配置cascade=CascadeType.PERSIT也對persist操作也可以獲得同樣的效果。
        // CascadeType.ALL包含CascadeType.PERSIST。
        @OneToOne(cascade=CascadeType.ALL)
        Son mySon
        
        public Father( int id, String name, Son mySon ){
            this.id = id;
            this.mySon = mySon;
            this.name = name;
        }
    }
                  

                
    final EntityManager manager = emf.createEntityManager();
    manager.getTransaction().begin;
    
    Son mySon = new Son();
    Father = new Father( 1, mySon );
    
    // 保存Father。由于OneToOne關(guān)系中配置casacade=CascadeType.ALL屬性,關(guān)聯(lián)的mySon會(huì)自動(dòng)地被持久化
    manager.persist( father );
    manager.getTransaction().commit();
    manager.close();
                 

                        
    Father father = manager.find( Father.class, new Integer( 1 ) );
            
    // 由于JDK1.5支持自動(dòng)轉(zhuǎn)型，也可以如下使用
            
    Father father = manager.find( Father.class, 1 );
    
    /* 
    *　或者,可以用Entity名字作為查找。但無法利用JDK 1.5的自動(dòng)轉(zhuǎn)型功能，
    *  需要使用對象作為查找主鍵，并需要對獲得Entity進(jìn)行轉(zhuǎn)型
    */
    
    Father father = (Father)manager.find( "com.redsoft.samples.Father", new Integer( 1 ) );
            
          

                
    transaction.begin();                
    Father father = manager.find( Father.class, 1 );
    
    // 更新原始數(shù)據(jù)類型
    father.setName( "newName" );
    
    // 更新對象引用
    Son newSon = new Son();
    father.setSon( newSon );
    
    
    // 提交事務(wù)，剛才的更新同步到數(shù)據(jù)庫
    transaction.commit();
                 

                
    transaction.begin();                
    
    Father father = manager.find( Father.class, 1 );
        
    // 如果father/son的@OneToOne的cascade=CascadeType.ALL，在刪除father時(shí)候，也會(huì)把son刪除。
    // 把cascade屬性設(shè)為cascade=CascadeType.REMOVE有同樣的效果。
    manager.remove( father );
        
    // 提交事務(wù)，剛才的更新同步到數(shù)據(jù)庫
    transaction.commit();
                 

                
    EntityManager entityManager = emf.createEntityManager();
    
    // 這時(shí)Father還是被EntityManager管理的
    Father father = manager.find( Father.class, 1 );
    
    // 當(dāng)entityManger關(guān)閉的時(shí)候，當(dāng)前被entityManager管理的Entity都會(huì)自動(dòng)的脫離EntityManager，狀態(tài)轉(zhuǎn)變?yōu)閐etached
    entityManager.close();
    
    // 脫離EntityManager后，我們?nèi)匀豢梢孕薷腇ather的屬性
    father.setName( "newName" );
    
    // 在稍后的，我們可以將father重新附和到一個(gè)新的或者原來的EntityManager中
    EntityManager newEntityManager = emf.createEntityManager();
    
    // 附合( merge )需要在事務(wù)中進(jìn)行
    newEntityManager.getTransaction().begin();
    newEntityManager.merge( father );
    
    // commit后father中的被修改的內(nèi)容會(huì)同步到數(shù)據(jù)庫。
    newEntityManager.getTransaction().commit();