Hibernate - createEntityManagerFactory太慢

Question

我對Hibernate相當陌生。我用Hibernate和JPA編寫了一個程序。問題是當我調用Persistence.createEntityManagerFactory（「name」）時，它至少需要3000毫秒（甚至8000毫秒）來返回一個EntityManagerFactory。

從我PersistenceCtrl的代碼是如下因素：

import javax.persistence.*; 

public class PersistenceCtrl { 

private EntityManager entityManager; 
private EntityManagerFactory entityManagerFactory; 

public PersistenceCtrl() { 
    startPersistenceCtrl(); 
} 

public EntityManager getEntityManager() { 
    return entityManager; 
} 

public void setEntityManager(EntityManager entityManager) { 
    this.entityManager = entityManager; 
} 

public EntityManagerFactory getEntityManagerFactory() { 
    return entityManagerFactory; 
} 

public void setEntityManagerFactory(EntityManagerFactory entityManagerFactory) { 
    this.entityManagerFactory = entityManagerFactory; 
} 

public void startPersistenceCtrl(){ 
    this.setEntityManagerFactory(Persistence.createEntityManagerFactory("name")); 
    this.setEntityManager(this.getEntityManagerFactory().createEntityManager());   
} 

public void closePersistenceCtrl(){ 
    //EntityTransaction et = this.getEntityManager().getTransaction(); 
    //et.begin(); 
    //this.getEntityManager().flush(); 
    //et.commit(); 
    this.getEntityManager().close(); 
    this.getEntityManagerFactory().close(); 
} 

public void saveObject(Object obj){ 
    EntityTransaction et = this.getEntityManager().getTransaction(); 
    et.begin(); 

    this.getEntityManager().persist(obj); 

    et.commit(); 
} 

public void removeObject(Object obj){ 
    EntityTransaction et = this.getEntityManager().getTransaction(); 
    et.begin(); 

    this.getEntityManager().remove(obj); 

    et.commit(); 
} 

} 

我的persistence.xml是如下因素：

<?xml version="1.0" encoding="UTF-8"?> 
<persistence xmlns="http://java.sun.com/xml/ns/persistence" 
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
      xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd" 
      version="2.0"> 
    <persistence-unit name="name"> 
     <provider>org.hibernate.ejb.HibernatePersistence</provider> 

    <!-- My classes --> 

    <properties> 
     <property name="hibernate.validator.apply_to_ddl" value="false"/> 
     <property name="hibernate.validator.autoregister_listeners" value="false"/> 
     <property name="hibernate.cache.provider_class" value="org.hibernate.cache.NoCacheProvider"/> 
     <property name="javax.persistence.validation.mode" value="ddl"/> 
     <property name="javax.persistence.jdbc.url" value="url"/> 
     <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/> 
     <property name="javax.persistence.jdbc.user" value="user"/> 
     <property name="javax.persistence.jdbc.password" value="password"/> 
     <property name="javax.persistence.jdbc.initialSize" value="2"/> 
     <property name="javax.persistence.jdbc.minIdle" value="0"/> 
     <property name="javax.persistence.jdbc.maxActive" value="10"/> 
     <!-- <property name="hibernate.hbm2ddl.auto" value="update"/> --> 
     <!-- <property name="javax.persistence.jdbc.minEvictableIdleTimeMillis" value="120000"/> --> 
     <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5InnoDBDialect"/> 
    </properties> 
</persistence-unit> 

這是正常的嗎？

從Hibernate中使用SessionFactory會更快嗎？

謝謝。

Answer 1

EntityManagerFactory是一個線程安全的對象，應該在應用程序的生命週期中只創建一次。如果創建需要3秒鐘，這應該不重要。

沒有理由關閉EntityManagerFactory並重新打開它，就像你似乎在做什麼。