Injecting all beans of the same type with CDI

Question

Suppose we have a package foos containing classes, which all of them implements some IFoo.

We also have a class, Baz which contains a data-member, List<IFoo> fooList. Is it possible to inject dynamically all those IFoo classes into fooList?

By the way, is it a common practice? (I'm new with the DI concept)

Jens Piegsa · Accepted Answer · 2016-02-14T12:04:21.940

20

Use the javax.enterprise.inject.Instance interface to dynamically obtain all instances of Foo:

import javax.annotation.PostConstruct;
import javax.enterprise.inject.Instance;
import javax.inject.Inject;

public class Baz {

    @Inject
    Instance<Foo> foos;

    @PostConstruct
    void init() {
        for (Foo foo : foos) {
            // ...
        }
    }
}

This totally makes sense, e.g. if you want to merge the results of multiple service provider implementations. You find a good study example here.

See also:

JSR-000346 Contexts and Dependency Injection for JavaTM EE 1.2,
Section 5.6. Programmatic lookup

edited Feb 14 '16 at 12:04

answered Feb 14 '16 at 11:24

Jens Piegsa

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Thank you. Haven't tried it yet but it looks promising :) – Elimination Feb 14 '16 at 18:25
does this work also with @Stateless Foo implementations? – Frank Nov 29 '17 at 13:55
@Frank I could not find any specific statement about EJBs in the specs for this case, but I can confirm that this works on WildFly and I assume that instance lookup is intended to be compatible between CDI and EJB world. – Jens Piegsa Nov 29 '17 at 22:42
1

@Jens If the type of the Instance is an interface it seems to work with non-stateless beans only. – Frank Dec 06 '17 at 15:46
@Frank Does your beans.xml contain `bean-discovery-mode="all"`? – Jens Piegsa Dec 06 '17 at 18:50
@Jens Yes, it does implicitly because my beans.xml is empty. – Frank Dec 19 '17 at 09:36

Injecting all beans of the same type with CDI

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