@Qualifier Annotation in spring

Tutorial Content: Spring tutorial for beginners

    Introduction to spring framework Dependency injection(ioc) in spring Spring hello world example in eclipse Spring java based configuaration Dependency injection via setter method in spring Dependency injection via constructor in spring Spring Bean scopes with examples Initializing collections in spring Beans Autowiring in spring Inheritance in Spring Spring ApplicationContext Spring lifetime callbacks BeanPostProcessors in Spring Annotation based Configuration in spring
you can have more than one bean of same type in your XML configuration but you want to autowire only one of them ,so @Qualifier removes confusion created by @Autowired by declaring exactly which bean is to autowired.

Example:

For configuring spring in your eclipse ide please refer hello world example

1.Country.java:

This is simple pojo class having some attributes so here country has name and object of Capital class.
Create Country.java under package org.arpit.javapostsforlearning.Copy following content into Country.java.

package org.arpit.javapostsforlearning;
import org.springframework.beans.factory.annotation.Autowired;
public class Country {

    String countryName;
    @Autowired
    @Qualifier("capitalA") 
    Capital capital;
    public String getCountryName() {
        return countryName;
    }
    public void setCountryName(String countryName) {
        this.countryName = countryName;
    }
    public Capital getCapital() {
        return capital;
    }
}

2.Capital.java

This is also simple pojo class having one attribute called "capitalName".
Create Capital.java under package org.arpit.javapostsforlearning.java.Above Country class contains object of this class.Copy following content into Capital.java

package org.arpit.javapostsforlearning;

public class Capital {

    String capitalName;

    public String getCapitalName() {
        return capitalName;
    }

    public void setCapitalName(String capitalName) {
        this.capitalName = capitalName;
    }
}

3.QualifierAnnotationInSpringMain.java

This class contains main function.Create QualifierAnnotationInSpringMain.java under package org.arpit.javapostsforlearning.Copy following content into QualifierAnnotationInSpringMain.java

 package org.arpit.javapostsforlearning;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class QualifierAnnotationInSpringMain{

    public static void main(String[] args) {
        ApplicationContext appContext = new ClassPathXmlApplicationContext("ApplicationContext.xml");

        Country countryObj = (Country) appContext.getBean("CountryBean");
        String countryName=countryObj.getCountryName();
        Capital capital=countryObj.getCapital();
        String capitalName=capital.getCapitalName();
        System.out.println(capitalName+" is capital of "+countryName);
       
    }
}

4.ApplicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context-3.0.xsd">
 <context:annotation-config/>
 <bean id="CountryBean" class="org.arpit.javapostsforlearning.Country">
  <property name="countryName" value="India" />
 </bean>
 <bean id="capitalA" class="org.arpit.javapostsforlearning.Capital">
  <property name="capitalName" value="Delhi" />
 </bean>
 <bean id="capitalB" class="org.arpit.javapostsforlearning.Capital">
  <property name="capitalName" value="Mumbai" />
 </bean>
</beans>

As you can note here we are having two beans of same type.In Country.java we have used @Qualifier("capitalA") it means we want to autowire capital property of country with bean id="capitalA" in XML configuration file.

5.Run it:

When you will run above application,you will get following as output.

Delhi is capital of India

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