java - What is javax.inject.Named annotation supposed to be used for?

Question

I am trying to understand the javax.inject package and I am not clear what the javax.inject.Named annotation is supposed to be used for. The Javadoc does not explain the the idea behind it.

Javadoc is at http://download.oracle.com/javaee/6/api/javax/inject/Named.html

I am using Spring 3.0 to write some sample programs, by putting @Named on a bean it seems to add it to the bean factory but the Javadoc description is so light I can't tell if that is the standard behavior or Spring specific behavior.

My questions are:

1. What is the difference between @Named and @Qualifier
2. How are you supposed to tell the Runtime system a class should be injectable in other classes what's the annotation for that? The equivalent of @Component in Spring?

Update 1 there is an excellent explanation of @Named and @Qualifier at Nice article about @Named and @Qualifier https://dzone.com/articles/java-ee6-cdi-named-components thanks @xmedeko for linking to it the comment below.

Answer 1

Use @Named to differentiate between different objects of the same type bound in the same scope.

@Named("maxWaitTime")
public long maxWaitTimeMs;

@Named("minWaitTime")
public long minWaitTimeMs;

Without the @Named qualifier, the injector would not know which long to bind to which variable.

• If you want to create annotations that act like @Named, use the @Qualifier annotation when creating them.

• If you look at @Named, it is itself annotated with @Qualifier.