[cdi-dev] [JBoss JIRA] (CDI-535) cdi instance injection ordering
Ochieng Marembo created CDI-535:
-----------------------------------
Summary: cdi instance injection ordering
Key: CDI-535
URL: https://issues.jboss.org/browse/CDI-535
Project: CDI Specification Issues
Issue Type: Feature Request
Components: Beans
Affects Versions: 2.0 (discussion)
Reporter: Ochieng Marembo
Priority: Optional
We should allow ordering of bean instance injection using the
```Instance<MyBeanInterface>``` when an instance injection is used.
h3. Use case:
Developer always define a kind of chain of processor beans, which may need to run in
specific order.
h3. Current scenario:
Using the Instance injection mechanism, a developer can inject multiple beans implementing
the same interface and iterate of them. In order to ensure ordering, the developer could
do one of the following:
#1
{code}
private Iterable<MyBeanInterface> myBeans;
@Inject
void injectBeans(@Any Instance<MyBeanInterface> myBeans) {
//the create order does some kind of ordering on the beans.
this.myBeans = createOrder(myBeans);
}
{code}
#2
This second option may be expensive if we have to order the beans everytime we execute the
logic, and if this bean is applicationscoped, it wont make sense to do the ordering in the
method call.
{code}
@Any
@Inject
private Instance<MyBeanInterface> myBeans;
public void doSomething() {
Iterable<MyBeanInterface> orderedbeans =
createOrder(myBeans.select(someQualifier));
}
{code}
h3. Our Proposal
We already have {code}javax.annotation.Priority{code} or any cdi specific annotation which
we can add to {code}MyBeanInterfaceImpl{code} so that on injection of an
{code}Instance<MyBeanInterface>{code}, all possible injection values are sorted
based on the {code}Priority.value(){code} and if no annotation is defined, defaults to
{code}Priority.value = Integer.MAX_VALUE{code}
{code}
public interface MyBeanInterface {}
@MyQualifier
@Priority(0)
public class MyFirstBean implements MyBeanInterface{
}
@MyQualifier
@Priority(2)
public class MySecondBean implements MyBeanInterface{
}
@ApplicationScoped
public class MyBeanProcessor {
//We expect that this injected instances shall be in order based on the @Priority
annotation
@Any
@Inject
private Instance<MyBeanInterface> myBeans;
}
{code}
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