Support automatic dependency injection for non-managed objects
--------------------------------------------------------------
Key: CDI-104
URL:
https://issues.jboss.org/browse/CDI-104
Project: CDI Specification Issues
Issue Type: Feature Request
Components: Beans
Affects Versions: 1.0
Reporter: Dan Allen
Allow objects created using the "new" keyword (or created by some other means)
to be injected automatically.
Conceptually it would look something like this:
@AutoInject
public class AccountService {
private final Account account;
@Inject
private PaymentProcessor paymentProcessor;
AccountService(Account account) {
this.account = account;
}
public void doPayment(double amount) {
paymentProcessor.processPayment(account, amount);
}
}
We could then create the object using new and the fields will still be injected:
AccountService a = new AccountService(account);
a.doPayment(10);
The inverse design would also be an option. An instance of Account could be retrieved from
JPA and the AccountService would be injected into it during construction.
To implement this feature may require a javaagent, which will modify the bytecode of
@AutoInject annotated classes as they are loaded, so that the constructor bytecode looks
up the values to inject and sets the injected field values appropriately. (There are other
options suggested in the linked thread).
The primary use case for this feature is to support rich domain models, though the
usefulness of this feature extends beyond this case, so I don't think the feature
should be dismissed if you don't agree with the rich domain models design.
The feature also brings the "new" keyword back into the picture of modern
programming. You can still create objects in the classic way, but benefit from modern
programming model patterns (specifically CDI).
Spring has a similar feature in it's AOP package:
http://static.springsource.org/spring/docs/3.0.x/spring-framework-referen...
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