[cdi-dev] [JBoss JIRA] (CDI-45) Optional Injection Points

Wed Oct 12 05:41:07 EDT 2016

In the Java SE 8 specific JSR 363 implementation Otavio and I tried to use
Optional, but see the comments in
https://github.com/unitsofmeasurement/uom-se/blob/master/src/main/java/tec/uom/se/spi/Range.java
it caused problems with the type-safe Quantity mechanism.

Can't recall the exact details, but there must have been a conflict when
using another generic type like Quantity<Q> or similar as <T> of Optional.
If the <T> of Bean<T> and Optional<T> were exactly the same it might work,
but if types with their own generic elements (Collection, Map or a
combination of several with different or nested generics) are used,
Optional seems to have some problems and limitations.

So trying to add these methods could be safer based on my experience with
Optional.

Werner

On Wed, Oct 12, 2016 at 10:43 AM, <cdi-dev-request at lists.jboss.org> wrote:

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>    1. [JBoss JIRA] (CDI-45) Optional Injection Points
>       (John Ament (JIRA))
>    2. [JBoss JIRA] (CDI-45) Optional Injection Points
>       (Martin Kouba (JIRA))
>    3. [JBoss JIRA] (CDI-45) Optional Injection Points
>       (John Ament (JIRA))
>    4. [JBoss JIRA] (CDI-45) Optional Injection Points
>       (Martin Kouba (JIRA))
>    5. [JBoss JIRA] (CDI-489) NonexistentConversationException
>       thrown at restore view or not? (Tomas Remes (JIRA))
>    6. [JBoss JIRA] (CDI-45) Optional Injection Points
>       (Matej Novotny (JIRA))
>    7. Moving on SERVLET_SPEC-116 (giving servlet beans to       servlet
>       spec) (Antoine Sabot-Durand)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 11 Oct 2016 16:50:00 -0400 (EDT)
> From: "John Ament (JIRA)" <issues at jboss.org>
> Subject: [cdi-dev] [JBoss JIRA] (CDI-45) Optional Injection Points
> To: cdi-dev at lists.jboss.org
> Message-ID:
>         <JIRA.12428685.1295838622000.12490.1476219000927 at Atlassian.JIRA>
> Content-Type: text/plain; charset=UTF-8
>
>
>     [ https://issues.jboss.org/browse/CDI-45?page=com.
> atlassian.jira.plugin.system.issuetabpanels:comment-
> tabpanel&focusedCommentId=13305781#comment-13305781 ]
>
> John Ament commented on CDI-45:
> -------------------------------
>
> I really like the idea of {{@Inject Optional<T>}}.  I may try to prototype
> a CDI extension that does it.
>
> > Optional Injection Points
> > -------------------------
> >
> >                 Key: CDI-45
> >                 URL: https://issues.jboss.org/browse/CDI-45
> >             Project: CDI Specification Issues
> >          Issue Type: Feature Request
> >          Components: Resolution
> >    Affects Versions: 1.0
> >            Reporter: Stuart Douglas
> >            Priority: Optional
> >             Fix For: TBD
> >
> >
> > There are occoasions where it may be useful for some injection points to
> be optional, e.g.
> > @Inject
> > @Optional
> > MyBean bean;
> > This would behave the same as a normal injection point, however it will
> not cause the deployment to fail if it is not satisified.
>
>
>
> --
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>
> ------------------------------
>
> Message: 2
> Date: Tue, 11 Oct 2016 17:21:00 -0400 (EDT)
> From: "Martin Kouba (JIRA)" <issues at jboss.org>
> Subject: [cdi-dev] [JBoss JIRA] (CDI-45) Optional Injection Points
> To: cdi-dev at lists.jboss.org
> Message-ID:
>         <JIRA.12428685.1295838622000.12514.1476220860783 at Atlassian.JIRA>
> Content-Type: text/plain; charset=UTF-8
>
>
>     [ https://issues.jboss.org/browse/CDI-45?page=com.
> atlassian.jira.plugin.system.issuetabpanels:comment-
> tabpanel&focusedCommentId=13305785#comment-13305785 ]
>
> Martin Kouba commented on CDI-45:
> ---------------------------------
>
> Note that {{Optional}} is not {{Serializable}} and is defined final. So
> there will be problems with injecting into beans with passivating scope
> (e.g. {{@SessionScoped}}).
>
> > Optional Injection Points
> > -------------------------
> >
> >                 Key: CDI-45
> >                 URL: https://issues.jboss.org/browse/CDI-45
> >             Project: CDI Specification Issues
> >          Issue Type: Feature Request
> >          Components: Resolution
> >    Affects Versions: 1.0
> >            Reporter: Stuart Douglas
> >            Priority: Optional
> >             Fix For: TBD
> >
> >
> > There are occoasions where it may be useful for some injection points to
> be optional, e.g.
> > @Inject
> > @Optional
> > MyBean bean;
> > This would behave the same as a normal injection point, however it will
> not cause the deployment to fail if it is not satisified.
>
>
>
> --
> This message was sent by Atlassian JIRA
> (v6.4.11#64026)
>
>
> ------------------------------
>
> Message: 3
> Date: Tue, 11 Oct 2016 18:38:00 -0400 (EDT)
> From: "John Ament (JIRA)" <issues at jboss.org>
> Subject: [cdi-dev] [JBoss JIRA] (CDI-45) Optional Injection Points
> To: cdi-dev at lists.jboss.org
> Message-ID:
>         <JIRA.12428685.1295838622000.12589.1476225480575 at Atlassian.JIRA>
> Content-Type: text/plain; charset=UTF-8
>
>
>     [ https://issues.jboss.org/browse/CDI-45?page=com.
> atlassian.jira.plugin.system.issuetabpanels:comment-
> tabpanel&focusedCommentId=13305798#comment-13305798 ]
>
> John Ament commented on CDI-45:
> -------------------------------
>
> Underestood.  The way I see it, for each Bean of type {{<T>}} there exists
> a Bean of type {{Optional<T>}} that shares the same qualifiers but has
> scope dependent.  Optional beans can't be looked up programmatically.
>
> Another way to do this is to add all methods from https://docs.oracle.com/
> javase/8/docs/api/java/util/Optional.html to Instance, which would be:
>
> * ifPresent
> * isPresent
> * orElse
> * orElseGet
> * orElseThrow
>
> So hm.
>
> > Optional Injection Points
> > -------------------------
> >
> >                 Key: CDI-45
> >                 URL: https://issues.jboss.org/browse/CDI-45
> >             Project: CDI Specification Issues
> >          Issue Type: Feature Request
> >          Components: Resolution
> >    Affects Versions: 1.0
> >            Reporter: Stuart Douglas
> >            Priority: Optional
> >             Fix For: TBD
> >
> >
> > There are occoasions where it may be useful for some injection points to
> be optional, e.g.
> > @Inject
> > @Optional
> > MyBean bean;
> > This would behave the same as a normal injection point, however it will
> not cause the deployment to fail if it is not satisified.
>
>
>
> --
> This message was sent by Atlassian JIRA
> (v6.4.11#64026)
>
>
> ------------------------------
>
> Message: 4
> Date: Wed, 12 Oct 2016 02:11:01 -0400 (EDT)
> From: "Martin Kouba (JIRA)" <issues at jboss.org>
> Subject: [cdi-dev] [JBoss JIRA] (CDI-45) Optional Injection Points
> To: cdi-dev at lists.jboss.org
> Message-ID:
>         <JIRA.12428685.1295838622000.12813.1476252661033 at Atlassian.JIRA>
> Content-Type: text/plain; charset=UTF-8
>
>
>     [ https://issues.jboss.org/browse/CDI-45?page=com.
> atlassian.jira.plugin.system.issuetabpanels:comment-
> tabpanel&focusedCommentId=13305826#comment-13305826 ]
>
> Martin Kouba commented on CDI-45:
> ---------------------------------
>
> -1 for adding those methods on {{Instance}} and -1 for introducing
> {{Optional}} built-in bean (mainly due to serialization issues and the need
> for special handling, e.g. disallow programatic lookup).
> {{Instance.getOptional().ifPresent(...)}} etc. is imho easier to
> understand.
>
> > Optional Injection Points
> > -------------------------
> >
> >                 Key: CDI-45
> >                 URL: https://issues.jboss.org/browse/CDI-45
> >             Project: CDI Specification Issues
> >          Issue Type: Feature Request
> >          Components: Resolution
> >    Affects Versions: 1.0
> >            Reporter: Stuart Douglas
> >            Priority: Optional
> >             Fix For: TBD
> >
> >
> > There are occoasions where it may be useful for some injection points to
> be optional, e.g.
> > @Inject
> > @Optional
> > MyBean bean;
> > This would behave the same as a normal injection point, however it will
> not cause the deployment to fail if it is not satisified.
>
>
>
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