织梦网站首页自动更新,网站开发培训课程表,北京网站如何制作,鹿泉外贸网站建设1.0jpa 2.0Java EE 7中的非同步持久性上下文 JPA 2.1引入了非同步持久性上下文的概念#xff0c;该概念允许对JPA实体管理器的刷新进行细粒度控制#xff0c;即通过显式调用EntityManager#xff03;joinTransaction 。 以前#xff0c;这默认情况下是JTA事务的结束#x… 1.0jpa 2.0 Java EE 7中的非同步持久性上下文 JPA 2.1引入了非同步持久性上下文的概念该概念允许对JPA实体管理器的刷新进行细粒度控制即通过显式调用EntityManagerjoinTransaction 。 以前这默认情况下是JTA事务的结束例如在典型的Stateless EJB中实体管理器会在方法结束时默认情况下开始和结束事务将其状态刷新到DB。 您可以在此处和此处阅读有关此内容的更多信息。 在Java EE 7之前的时代EE 5和EE 6也有可能 可以对Java EE 5和6进行调整以实现与Java EE 7中非同步持久性上下文所获得的结果相同的结果。 想象一下一个用例其中按顺序使用流程之类的向导编辑客户详细信息例如屏幕1中的地址信息屏幕2中的联系信息等。您希望在客户输入是但不希望将整个状态推送到数据库直到该过程完成即用户输入了所有类别的信息 package com.abhirockzz.conversationalee;import com.abhirockzz.conversationalee.entity.Customer;
import java.util.Date;
import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import javax.ejb.Remove;
import javax.ejb.Stateful;
import javax.ejb.TransactionAttribute;
import javax.ejb.TransactionAttributeType;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.PersistenceContextType;Stateful
TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED)
public class CustomerEditorFacade{PersistenceContext(type PersistenceContextType.EXTENDED)EntityManager em;Inject //this wont work in Java EE 5Principal authenticatedUser;private Customer customer;PostConstructpublic void init(){System.out.println(CustomerEditorFacade created at new Date().toString()); }PreDestroypublic void destroy(){System.out.println(CustomerEditorFacade destroyed at new Date().toString()); }//step 1public void updateCity(String custID, String city){String custID authenticatedUser.getName(); //assume we have an authenticated principal which is the same as the customer ID in the DatabaseCustomer customerFromDB em.find(Customer.class, Integer.valueOf(custID)); //obtain a managed entitycustomerFromDB.setCity(city); //no need to call em.persistcustomer customerFromDB; //just switch references//Customer state will NOT be pushed to DB}//step 2public void updateEmail(String email){customer.setEmail(email); //not pushed to DB yet}TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)public void save(){//dummy method to trigger transaction and flush EM state to DB}Removepublic void finish(){//optional method to provide a way to evict this bean once used//not required if this is session scoped}} 代码注释是自我解释希望如此 干杯! 翻译自: https://www.javacodegeeks.com/2015/12/pre-java-ee-7-alternative-jpa-2-1-unsynchronized-persistence-context.html1.0jpa 2.0
