[cdi-dev] [JBoss JIRA] (CDI-552) Add support for injection, decorators and interceptors on "new-ed" objects

[Rogerio Liesenfeld (JIRA)]

Rogerio Liesenfeld created CDI-552:
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             Summary: Add support for injection, decorators and interceptors on "new-ed" objects
                 Key: CDI-552
                 URL: https://issues.jboss.org/browse/CDI-552
             Project: CDI Specification Issues
          Issue Type: Epic
          Components: Beans, Decorators, Interceptors, Resolution
    Affects Versions: 2.0-EDR1
            Reporter: Rogerio Liesenfeld


The current CDI programming model is not friendly to object-oriented code or proper class design, and does not support true POJOs.

With this I mean:
1) For object-oriented code, I need to be able to instantiate and use *stateful*, short-lived, objects, while still having @Inject fields in it. I shouldn't be forced to have a stateless (non-OO) class (ie, a <a href="http://martinfowler.com/eaaCatalog/transactionScript.html">Transaction Script</a>).
2) Most classes in a business app are not meant to be used as subclasses, ie, they are not designed for extension; therefore, I should be able to make them `final` (see http://lcsd05.cs.tamu.edu/slides/keynote.pdf, page 26, or item 17 in the <a href="http://www.amazon.com/Effective-Java-2nd-Joshua-Bloch/dp/0321356683">book</a>).
3) For a class to truly be a POJO, I must be able to make *full use* of the Java language when designing and implementing it; arbitrary constraints like "can't be final", "can't have final instance fields", "cannot be instantiated directly", etc. prevent it from being a "plain-old" Java object.

Specifically, what I want is to be able to write the following in a JSF/CDI backing bean for a web UI:

MyBusinessService businessOp = new MyBusinessService(fieldFromUI1, fieldFromUI2, listWithMoreDataFromUI);
businessOp.performSomeBusinessOperation(otherArgs);

String result1 = businessOp.getResultXyz();
List<result> moreResultData = businessOp.getFinalData();

... while having MyBusinessService be a CDI bean containing one or more @Inject/@PersistenceContext fields (typically, an EntityManager and perhaps other service beans).

Without this ability, application developers are forced to create procedural Transation Scripts (stateless service class, which tend to have low cohesion).

For a CDI implementation to do this, it will need to use the java.lang.instrument API, like others tools (AspectJ, JBoss AOP, JBoss Byteman, JaCoCo, JMockit) already do.

Also, for reference, the Spring framework already supports it for some time: http://docs.spring.io/spring/docs/3.0.0.M3/spring-framework-reference/html/ch08s08.html



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