CDI Qualifier

Using Qualifiers

• use qualifiers to provide various implementations of a particular bean type

• qualifier is an annotation that is applied to a bean

  • @Target({METHOD, FIELD, PARAMETER, TYPE})

  • @Retention(RUNTIME)

• using a qualifier:

  • apply annotation to a bean

  • without a qualifier, @Default is automatically applied

A sample qualifier:

package greetings;

import static java.lang.annotation.ElementType.FIELD;

import static java.lang.annotation.ElementType.METHOD;

import static java.lang.annotation.ElementType.PARAMETER;

import static java.lang.annotation.ElementType.TYPE;

import static java.lang.annotation.RetentionPolicy.RUNTIME;

import java.lang.annotation.Retention;

import java.lang.annotation.Target;

import javax.inject.Qualifier;

@Qualifier

@Retention(RUNTIME)

@Target({TYPE, METHOD, FIELD, PARAMETER})

public @interface Informal {}

Qualifier with members

Members further discriminate qualifier.

@Nonbinding member will not discriminate qualifier

Multiple Qualifiers

The the qualifiers will combine