<HTML><BODY><p>Hi Matej,<br><br>I meant the following (in previous example I had a mistake - called Parent Child and Child Parent)<br>, now without this mistake:<br>1) <br>public class Parent {<br><br> @Inject<br> private Instance<SimpleFoo> fooInstance;<br><br> private SimpleFoo foo;<br><br> protected SimpleFoo newFoo() {<br> return fooInstance.get();<br> }<br><br> @PostConstruct<br> private void doPostConstruct() {<br> foo = newFoo();<br> }<br>}<br><br>public class Child extends Parent {<br><br> @Inject<br> private Instance<AdvancedFoo> fooInstance;<br><br> @Override<br> protected AdvancedFoo newFoo() {<br> return fooInstance.get();<br> }<br>}<br><br><br>2) <br><br>public class Parent {<br><br> @Inject<br> protected BeanManager beanManager;<br><br> private SimpleFoo foo;<br><br> protected SimpleFoo newFoo() {<br> SimpleFoo foo = constructing bean with BM;<br> return foo;<br> }<br><br> @PostConstruct<br> private void doPostConstruct() {<br> foo = newFoo();<br> }<br>}<br><br>public class Child extends Parent {<br><br> @Override<br> protected AdvancedFoo newFoo() {<br> AdvancedFoo foo = constructing bean with BM;<br> return foo;<br> }<br>}<br><br>Thank you for your explanation of Typed. I got it.<br><br>Best regards, Alex<br></p><blockquote style="border-left:1px solid #0857A6; margin:10px; padding:0 0 0 10px;">
Среда, 30 августа 2017, 10:51 +03:00 от Matej Novotny <manovotn@redhat.com>:<br>
<br>
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<div id="style_15040794960000000794_BODY">1) If you inject Instance<T>, you still have the ambiguous dependency issue for any class which does have a subclass.<br>
E.g. from your sample:<br>
<br>
@Inject<br>
Instance<SimpleFoo> instance;<br>
<br>
//within some method<br>
instance.get(); -> this will blow up because you have two beans which have SimpleFoo type (SimpleFoo and AdvancedFoo)<br>
<br>
2) I don't understand what you mean by this. How does BM help here?<br>
<br>
<br>
Sidenote: <br>
You might want to try and use what Martin said - limiting the types of a bean with @Typed(MyClass.Foo).<br>
That way you have control over the bean types and can further manupulate the injection.<br>
Limit all your children to only the actual subclass type they have:<br>
<br>
@Dependent<br>
@Typed(AdvancedFoo.class)<br>
public class AdvancedFoo extends SimpleFoo {<br>
// this ben now only has a bean of AdvancedFoo, e.g. it does not fit into injection point for SimpleFoo<br>
} <br>
<br>
And then override the initializer methods like this:<br>
<br>
@Dependent<br>
public class Parent extends Child {<br>
<br>
@Inject<br>
@Override<br>
protected void setFoo(AdvancedFoo foo) {<br>
this.foo = foo; // assuming foo is a protected field<br>
}<br>
}<br>
<br>
Matej<br>
<br>
<br>
----- Original Message -----<br>
> From: "Alex Sviridov" <<a href="mailto:ooo_saturn7@mail.ru">ooo_saturn7@mail.ru</a>><br>
> To: "weld-dev" <<a href="mailto:weld-dev@lists.jboss.org">weld-dev@lists.jboss.org</a>><br>
> Sent: Tuesday, August 29, 2017 8:54:47 PM<br>
> Subject: Re: [weld-dev] How to make method injection when bean subclass is required in Weld?<br>
> <br>
> I thought here, and would like to share my ideas hoping to get comments from<br>
> more experienced people.<br>
> <br>
> First of all I came to conclusion that CDI works badly with cases when we<br>
> need<br>
> to change field values in super classes. If there is a lot of inheritance as<br>
> in my case:<br>
> ParentA, ChildA0, ChildA1.., ParentB, ChildB0, ChildB1..,... then situation<br>
> is<br>
> becoming very bad. Maybe in future there will be other solutions in CDI<br>
> specs.<br>
> <br>
> I found two additional ways that can be used. 1) Inject not beans but<br>
> instances,<br>
> + method SimpleFoo newFoo {return Instance<SimpleFoo>.get} + overriding.<br>
> 2) Inject BeanManager + method SimpleFoo newFoo() {beanManager...} +<br>
> overriding.<br>
> <br>
> Maybe such ways can be named lazy/postponed initialization with overriding<br>
> support....<br>
> <br>
> Best regards, Alex<br>
> <br>
> <br>
> <br>
> <br>
> Вторник, 29 августа 2017, 18:22 +03:00 от Martin Kouba <<a href="mailto:mkouba@redhat.com">mkouba@redhat.com</a>>:<br>
> <br>
> Hi Alex,<br>
> <br>
> that's an interesting question. Indeed, qualifiers are the way to go if<br>
> you need to keep the method signature.<br>
> <br>
> Another way could be to override the setFoo() method so that the Child<br>
> initializer is ignored and add a new method to inject AdvancedFoo:<br>
> <br>
> @Override<br>
> protected void setFoo(SimpleFoo foo) { // Do nothing }<br>
> <br>
> @Inject<br>
> void setAdvancedFoo(AdvancedFoo foo) {<br>
> super.setFoo(foo);<br>
> }<br>
> <br>
> However, note that right now there are the following beans:<br>
> <br>
> SimpleFoo with bean types Object, SimpleFoo<br>
> AdvancedFoo -> Object, SimpleFoo, AdvancedFoo<br>
> <br>
> So if you do @Inject SimpleFoo you get ambiguous dependency exception<br>
> because both SimpleFoo and AdvancedFoo are eligible for injection.<br>
> <br>
> To resolve this you need to use qualifiers or restrict the bean types of<br>
> AdvancedFoo:<br>
> <br>
> @Typed(AdvancedFoo.class)<br>
> class AdvancedFoo extends SimpleFoo {}<br>
> <br>
> HTH<br>
> <br>
> Martin<br>
> <br>
> <br>
> Dne 29.8.2017 v 15:09 Matej Novotny napsal(a):<br>
> > Hi Alex,<br>
> > <br>
> > no need to be sorry, you have come to the right place :)<br>
> > As for your question, the simplest thing is probably to use qualifiers.<br>
> > <br>
> > Create your own like this:<br>
> > <br>
> > @Qualifier<br>
> > @Retention(RetentionPolicy.RUNTIME)<br>
> > @Target({ ElementType.TYPE, ElementType.PARAMETER, ElementType.FIELD,<br>
> > ElementType.METHOD })<br>
> > public @interface MyQualifier {}<br>
> > <br>
> > <br>
> > And then change your AdvancedFoo class to use the qualifier:<br>
> > <br>
> > @Dependent<br>
> > @MyQualifier<br>
> > public class AdvancedFoo extends SimpleFoo {<br>
> > }<br>
> > <br>
> > And accordingly, the init method which uses injection should then look like<br>
> > this:<br>
> > <br>
> > @Dependent<br>
> > public class Parent extends Child {<br>
> > <br>
> > @Inject<br>
> > @Override<br>
> > protected void setFoo(@MyQualifier SimpleFoo foo) {<br>
> > super.setFoo(foo);<br>
> > }<br>
> > }<br>
> > <br>
> > Does this answer your question?<br>
> > <br>
> > Matej<br>
> > <br>
> > ----- Original Message -----<br>
> >> From: "Alex Sviridov" < <a href="mailto:ooo_saturn7@mail.ru">ooo_saturn7@mail.ru</a> ><br>
> >> To: "weld-dev" < <a href="mailto:weld-dev@lists.jboss.org">weld-dev@lists.jboss.org</a> ><br>
> >> Sent: Tuesday, August 29, 2017 1:46:23 PM<br>
> >> Subject: [weld-dev] How to make method injection when bean subclass is<br>
> >> required in Weld?<br>
> >> <br>
> >> Hi all,<br>
> >> <br>
> >> I am really sorry for writing to this mailing list, but I checked all user<br>
> >> forums and chats and saw that they are very old.<br>
> >> <br>
> >> I would be very thankful if someone gives suggestion for solving the<br>
> >> following problem.<br>
> >> I have a child and parent class. Child has SimpleFoo, Parent needs Advaced<br>
> >> foo. So,<br>
> >> <br>
> >> @Dependent<br>
> >> public class SimpleFoo {<br>
> >> }<br>
> >> <br>
> >> @Dependent<br>
> >> public class AdvancedFoo extends SimpleFoo {<br>
> >> }<br>
> >> <br>
> >> @Dependent<br>
> >> public class Child {<br>
> >> <br>
> >> private SimpleFoo foo;<br>
> >> <br>
> >> @Inject<br>
> >> protected void setFoo(SimpleFoo foo) {<br>
> >> this.foo = foo;<br>
> >> }<br>
> >> }<br>
> >> <br>
> >> @Dependent<br>
> >> public class Parent extends Child {<br>
> >> <br>
> >> @Inject<br>
> >> @Override<br>
> >> protected void setFoo(SimpleFoo foo) { //How to inject here AdvancedFoo?<br>
> >> super.setFoo(foo);<br>
> >> }<br>
> >> }<br>
> >> <br>
> >> How to inject in Parent AdvancedFoo? I know that I can do it via<br>
> >> constructor<br>
> >> injection<br>
> >> but I need method injection. How to do it? Can it be done without using<br>
> >> names<br>
> >> (like MyBean1)<br>
> >> but only using classes (AdvancedFoo)?<br>
> >> <br>
> >> Best regards, Alex<br>
> >> <br>
> >> <br>
> >> <br>
> >> <br>
> >> <br>
> >> --<br>
> >> Alex Sviridov<br>
> >> <br>
> >> _______________________________________________<br>
> >> weld-dev mailing list<br>
> >> <a href="mailto:weld-dev@lists.jboss.org">weld-dev@lists.jboss.org</a><br>
> >> <a href="https://lists.jboss.org/mailman/listinfo/weld-dev" target="_blank">https://lists.jboss.org/mailman/listinfo/weld-dev</a><br>
> > _______________________________________________<br>
> > weld-dev mailing list<br>
> > <a href="mailto:weld-dev@lists.jboss.org">weld-dev@lists.jboss.org</a><br>
> > <a href="https://lists.jboss.org/mailman/listinfo/weld-dev" target="_blank">https://lists.jboss.org/mailman/listinfo/weld-dev</a><br>
> > <br>
> <br>
> --<br>
> Martin Kouba<br>
> Senior Software Engineer<br>
> Red Hat, Czech Republic<br>
> <br>
> <br>
> _______________________________________________<br>
> weld-dev mailing list<br>
> <a href="mailto:weld-dev@lists.jboss.org">weld-dev@lists.jboss.org</a><br>
> <a href="https://lists.jboss.org/mailman/listinfo/weld-dev" target="_blank">https://lists.jboss.org/mailman/listinfo/weld-dev</a><br>
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