[014-3] Spring @Qualifier Annotation

Spring @Qualifier Annotation

(원문 위치 : http://www.tutorialspoint.com/spring/spring_qualifier_annotation.htm )

동일 타입의 하나이상의 bean을 생성하고 속성(property)으로 그중 단지 하나와 wire되기를 원하는 상황이 있을 것이다. 이러한 경우 @Autowired와 함께 @Qualifier annotation을 사용하여 wire되어질 정확한 bean을 명시하여 혼란을 제거한다. 아래 예제는 @Qualifier의 예제이다.

Example:

[003] HelloWorld Exampe 강좌를 참조하여 프로젝트를 생성한다.

Student.java:

package com.tutorialspoint;

public class Student {
   private Integer age;
   private String name;

   public void setAge(Integer age) {
      this.age = age;
   }
   
   public Integer getAge() {
      return age;
   }

   public void setName(String name) {
      this.name = name;
   }
   
   public String getName() {
      return name;
   }
}

Profile.java: student 속성(property)에 @Autowired 속성을 사용하였고, 또한  @Qualifier 속성으로 student1 bean정의를 사용하여 속성을 생성할 것을 나타내고 있다.

package com.tutorialspoint;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;

public class Profile {
   @Autowired
   @Qualifier("student1")
   private Student student;

   public Profile(){
      System.out.println("Inside Profile constructor." );
   }

   public void printAge() {
      System.out.println("Age : " + student.getAge() );
   }

   public void printName() {
      System.out.println("Name : " + student.getName() );
   }
}

MainApp.java:

package com.tutorialspoint;

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

public class MainApp {
   public static void main(String[] args) {
      ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");

      Profile profile = (Profile) context.getBean("profile");

      profile.printAge();
      profile.printName();
   }
}

Beans.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/>

   <!-- Definition for profile bean -->
   <bean id="profile" class="com.tutorialspoint.Profile">
   </bean>

   <!-- Definition for student1 bean -->
   <bean id="student1" class="com.tutorialspoint.Student">
      <property name="name"  value="Zara" />
      <property name="age"  value="11"/>
   </bean>

   <!-- Definition for student2 bean -->
   <bean id="student2" class="com.tutorialspoint.Student">
      <property name="name"  value="Nuha" />
      <property name="age"  value="2"/>
   </bean>

</beans>

실행 결과는 아래와 같다.

Inside Profile constructor.
Age : 11
Name : Zara