JPA CDI将DAO注入实体 [英] JPA CDI Injecting DAO into an Entity

问题描述

我是JPA和CDI的新手，我正在尝试使用这些框架创建一个企业应用程序。

I'm new to JPA and CDI and I'm trying to create an enterprise application using these frameworks.

我得到如何注入豆子，保持一切整洁和无状态。我也得到JPA加载关系等等，所以我不用再担心了。我仍然使用我的DAO的具体的查找方法和交流创建新的实体。

I get how I can inject into beans and keep everything tidy and stateless. I also get that JPA loads relations etc. for me so that I don't have to worry about it anymore. I still use my DAO's for specific find methods and ofcourse to create new entities.

我明白，我不想把东西注入我的实体，因为他们是由JPA管理，我需要使用新的关键字创建一个新的实体（而不是加载）。

I understand that I don't want to be injecting stuff into my entities since they're managed by JPA and I need to use the new keyword to create a new entity (instead of loading).

我习惯于用其他类管理我的实体，例如，如果我们有一个用户和一个组，我使用无状态bean来管理组（创建新的，找到等等），这个无状态的bean使用我的DAO来检索和发送数据。

I'm used to managing my entities with other classes, for example if we have a User and a Group I use a stateless bean to manage the group (create new ones, find ones etc) and this stateless beans uses my DAO to retrieve and send the data.

我使用组实体来管理用户（也许这是错误的？）但我不想将DAO注入到组中，因为它是一个实体。我知道这种设计有问题，但我找不到最佳实践。

I use the Group entity to manage the users (maybe this is wrong?) but I don't want to inject the DAO into the Group since it's an entity. I know there's something wrong in this design but I can't find the best practice for this.

所有管理类都应该是EJB吗？我习惯于为我的逻辑创建域类，我应该把这个概念放在远方，把我所有的逻辑放在EJB中，并使用Entities来保存数据？

Should all management classes be EJBs? I'm used to creating Domain classes for my logic, should I throw this concept away, put all my logic in EJBs and use the Entities for holding data only?

推荐答案

我使用组实体来管理用户（也许这是错误的）但是
我不想将DAO注入到组中它是一个实体。 I
知道这个设计有问题，但是我找不到最好的
的做法。

I use the Group entity to manage the users (maybe this is wrong?) but I don't want to inject the DAO into the Group since it's an entity. I know there's something wrong in this design but I can't find the best practice for this.

如果组具有用户，则将其映射为集合（可能为OneToMany）。

If a Group has Users, map this as a collection (possibly OneToMany).

使用另一个不同的bean来封装持久化操作，例如一个 GroupService 或一个 GroupDao 。在这个bean中，您将注入一个负责持久化的EntityManger（管理用户和组）。

Use another distinct bean to encapsulate persistence operations, e.g. a GroupService or a GroupDao. In this bean you will inject an EntityManger, which is responsible for persistence ("manage Users and Groups").

本教程应该给您一个开始。

所有管理类都应该是EJB吗？

Should all management classes be EJBs?

当然不一定。但是，在不知道你的要求的情况下，它有点困难（见：不可能）。我建议您添加更多信息的孤立问题，然后讨论您的问题更容易...

Certainly not necessarily. But it's a bit hard (read: impossible) to tell without knowing your requirements. I suggest that you add isolated questions with more information, then it's way easier to discuss your problem...

作为经验法则：尝试分离实体（组，用户）从业务逻辑和持久化操作（GroupService，... Dao）。

As a rule of thumb: Try separating entities (Group, User) from business logic and persistence operations (GroupService, ...Dao).

我发现 这本书 给出了关于后J2EE模式的很好的概述和讨论。

I find this book gives an excellent overview and discussion about post J2EE pattern.

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