在EJB方法/ @RequestScoped和@Stateless之间传递状态 [英] Passing state between EJB methods / @RequestScoped and @Stateless

问题描述

我有一个@RequestScoped CDI bean，我想变成一个EJB来获得声明性的事务。 （我在EJB 3.1，Java EE 6）

目前，我在子例程之间传递状态，假设实例仅用于单个请求。如果我现在添加 @Stateless ，那么假设会改变。

例如，我想做一些类似

  @Stateless 
 @Named 
 @RequestScoped 
 public class Foo {
 private String VAR1; //无法在@Stateless中使用实例vars？ 
 private String var2; 
 
 public void transactionForRequest（）{
 var1 = value; 
 var2 = value; 
 .... 
子例程（）; 
} 
} 
  

我认为上述不行 - 那是正确？

我正在考虑两种选择：

• 使用@Stateful而不是@Stateless ，以及@Named和@RequestScoped。


• 保持@Stateless，并使用 EJBContext.getContextData 映射替换实例变量。

哪个更好？还有另外一些我不想的呢？ （除了等待Java EE 7或切换到Spring。： - ））

解决方案

虽然 @Stateless ， @Singleton 和 @MessageDriven 可以通过 @Inject ，他们不能 @RequestScoped 或任何其他范围。只有 @Stateful 模型是足够灵活的支持范围。换句话说，您可以将 @Stateful bean类本身注释为 @RequestScoped ， @ SessionScoped 等。

简单来说， @Stateless ， @Singleton 已经有固定的范围。 @Singleton 本质上是 @ApplicationScoped 和 @Stateless 作为一些构成范围，如 @InvocationScoped （如果存在）。 @MessageDriven bean的生命周期完全取决于驱动它的连接器，因此也不允许有用户定义的范围。

另请参见 https://stackoverflow.com/a/8720148/190816

I have a @RequestScoped CDI bean that I want to turn into an EJB to get declarative transactions. (I'm on EJB 3.1, Java EE 6)

Currently, I am passing state between subroutines, under the assumption that the instance is only used in a single request. If I add @Stateless now that assumption would change.

For example, I want to do something like

@Stateless
@Named
@RequestScoped
public class Foo {
  private String var1; // can't use instance vars in @Stateless?
  private String var2;

  public void transactionForRequest() {
    var1 = value; 
    var2 = value;
    ....
    subroutine();
  }
}

I assume the above doesn't work- is that correct?

I am contemplating two alternatives:

• Use @Stateful instead of @Stateless, along with @Named and @RequestScoped.
• Keep @Stateless and use EJBContext.getContextData map to replace instance variables.

Which is better? And is there some other alternative I'm not thinking of? (Besides wait for Java EE 7 or switch to Spring. :-))

解决方案

While @Stateless, @Singleton and @MessageDriven can have scoped references injected via @Inject, they cannot be @RequestScoped or any other scope. Only the @Stateful model is flexible enough to support scopes. In other words, you can annotate the @Stateful bean class itself as @RequestScoped, @SessionScoped, etc..

In simple terms @Stateless, @Singleton have fixed "scopes" already. @Singleton is essentially @ApplicationScoped and @Stateless would perhaps be some made-up scope like @InvocationScoped, if that existed. The lifecycle of an @MessageDriven bean is entirely up to the Connector that drives it and is therefore also not allowed to have user-defined scope.

See also https://stackoverflow.com/a/8720148/190816

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