CDI交易管理：@Transactional如何工作？ [英] CDI Transaction Management: How does @Transactional work?

问题描述

  @Named（myBean）$ b在会话范围内拥有简单的CDI bean $ b @SessionScoped 
 public class MyBean实现Serializable {
 private static final long serialVersionUID = 1L; 
 
 @Inject 
 EntityManager em; 
 ... 
 
 @Transactional 
 private void testInsert（）{
 long t = System.currentTimeMillis（）; （int i = 1; i <50000; i ++）
 
 {
 create（i）; 
} 
 System.out.println（Time：+ Long.toString（System.currentTimeMillis（） -  t））; 
} 
 
 private void create（int i）{
 Project p = new Project（Project+ i）; 
 em.persist（p）; 
} 
} 
  

现在，通过EL＃{myBean .testInsert}有两件事情似乎很奇怪：

1）将@ Transactional-annotation移到方法create（int）我得到：

javax.persistence.TransactionRequiredException：JBAS011469：
执行此操作需要执行事务（使用
事务或扩展持久性上下文）

2）用@Transactional装饰testInsert（），该函数立即返回，但JPA仍然在后台更新数据库线。该过程需要2分钟才能完成只有50000条记录的INSERT。在这个过程中关闭Java EE应用程序服务器时，后台进程停止，因此在我看来 - testInsert（）不是事务性的。

这里误会？如何正确管理交易？

解决方案

@ javax.transaction.Transactional 是在Java EE 7中引入的拦截器绑定。由CDI为您的bean注入的代理将拦截注释的方法调用以将其包装在事务中。

拦截器不适用于私有方法 - 我想这是你的例子的主要问题。

Having a simple CDI bean in session scope with an entity manager injected:

@Named("myBean")
@SessionScoped
public class MyBean implements Serializable {
    private static final long serialVersionUID = 1L;

    @Inject
    EntityManager em;
   ...

    @Transactional
    private void testInsert() {
        long t = System.currentTimeMillis();

        for (int i=1; i<50000; i++) {  
            create(i);
        }
       System.out.println("Time: " + Long.toString(System.currentTimeMillis()-t));
    }

    private void create(int i) {
        Project p = new Project("Project " + i);
        em.persist(p);
    }
}

Now, when calling the function via EL #{myBean.testInsert} there are two things that seems to be very strange:

1) Moving the @Transactional-annotation to the method create(int) I get:

javax.persistence.TransactionRequiredException: JBAS011469: Transaction is required to perform this operation (either use a transaction or extended persistence context)

2) Decorating testInsert() with @Transactional instead, the function returns instantly but JPA is still updating the database within a background thread. The process needs 2 minutes to finish INSERT of only 50000 records. When shutting down the Java EE-application server within the process, the background process stops and thus - in my opinion - testInsert() is not transactional.

What is my general misunderstanding here? How to manage transactions properly?

解决方案

@javax.transaction.Transactional is an interceptor binding introduced in Java EE 7. The proxy injected by CDI for your bean will intercept annotated method calls to wrap them in a transaction.

Interceptors do not work for private methods - I suppose that's the main problem with your example.

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