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InfoQ Homepage News Gavin King Provides Web Beans Preview (JSR 299) Featuring Guice Inspired Dependency Injection

Gavin King Provides Web Beans Preview (JSR 299) Featuring Guice Inspired Dependency Injection

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Gavin King has released a 4 part preview (one, two, three, four) of the upcoming Web Beans (JSR 299) specification. Web Beans was initiated by JBoss to fill a gap in JEE 5 involving the web tier and transactional tier. Members of the JSR include Sun, Oracle, and Google. King states that the component model is deeply influenced by Google Guice and Seam.

The first article in the series provides an introduction to the technology:

...Web Beans is a component model that is compatible with technologies in both tiers. Web Beans integrates with both JSF and EJB3, allowing an EJB3 session bean to act as a JSF managed bean, thus unifying the two component models. Additionally, Web Beans provides a conversation model and persistence context management, thereby solving state management problems and optimistic transaction management problems that affect JSF and JPA...A Web Bean is an application component containing business logic. A Web Bean may be called directly from Java code, or it may be invoked via Unified EL. A Web Bean may access transactional resources. Dependencies between Web Beans are managed automatically by the Web Beans container. Most Web Beans are stateful and contextual. The lifecycle of a Web Bean is always managed by the container...

The second article in the series covers the injection, binding annotations, and component types of the specification. Supported injection types are:

  • Direct Field
  • Method
  • Constructor
  • Parameter

The third article in the series provides examples of declaring components via XML instead of annotations. Finally King covers scopes, contexts, and resolver methods. With available scope types as follows:

  • @RequestScoped
  • @SessionScoped
  • @ApplicationScoped
  • @ConversationScoped

Expectedly such a large amount of content has created a similar amount of commentary. One of the more interesting observations is:

There's been a lot of talk over the past few years that perhaps Interface 21 should push to formally make the Spring Framework a part of the JEE specs -- it seemed like it might be possible with Rod Johnson officially declaring his support for JEE 6... well it looks like "Crazy" Bob Lee and the team behind Guice may have found a back door to get themselves into the party first -- according to a new series of articles about the upcoming Web Beans, the new spec is actually influenced by a combination of Seam and Guice ... I find these articles interesting in that Google has apparently taken the JBoss approach to supporting the JCP -- that is, create an independent product to fill a whole in the JEE specs, and then use the JCP to make that product into a spec itself (take a look at the JPA for a previous example)...

Similar comments can be found with the articles themselves:

Interesting - the tie in to Seam is obvious, but this is the first I've seen of any involvement from the Guice team... I can't help but wonder if the term 'Web Beans' is accurate...

To which King replies:

Probably, Seam will eventually be split into two layers. 1) The core component engine, which will evolve into the Web Beans RI 2) The framework layer which will provide all the built-in components, JSF components, etc ... Bob has contributed a huge amount of effort and ideas to the specification.

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