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Tags CDI, Java, Tip, Tutorial
When developing plugin architectures with IOC, it is useful to be able to iterate over the available beans of a given type which are known to the IO container.
In CDI, this is easy to do, but it is not obvious how from the Weld documentation unless you do a bit of digging and searching.
This post here gives a sample application which does it. The crucial code snippet which does the business is here:-
private @Named @Produces ArrayList<String> wilsons = new ArrayList<String>();
@Inject
void initWilsonRacquets(@Any Instance<WilsonType> racquets) {
for (WilsonType racquet : racquets) {
wilsons.add(racquet.getWilsonRacquetType());
}
}
The intance keyword (used with @Any) exposes an iterator which lets you iterate the available beans. In the above sample they are added to a collection, but you could equally call methods on them as you iterate if you don’t need to keep them.
The Weld documentation describes this on page 25, with the following sample fragment:-
@Inject
void initServices(@Any Instance<Service> services) {
for (Service service: services) {
service.init();
}
}
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