자바 어노테이션의 모든것

MyBean.java 가 XML/어노테이션/자바 컨피그레이션을 통해 어떻게 객체로 만들어지는지 살펴보도록하자.

( 1 ) XML 을 통한 설정

Beans:

스프링 컨테이너 안에 만들고싶은 자바 클래스들 ("benas") 이다. 두번째 빈은 첫번째 빈을 DI 받고 있다.

MyBean.java

package com.hmkcode.spring.beans;
 
public class MyBean {
 
    private String name;
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    @Override
    public String toString() {
        return "MyBean [name=" + name + "]";
    }
 
}

AnotherBean.java

package com.hmkcode.spring.beans;
 
public class AnotherBean {
 
    private MyBean myBean;
 
    public MyBean getMyBean() {
        return myBean;
    }
 
    public void setMyBean(MyBean myBean) {
        this.myBean = myBean;
    }
 
    @Override
    public String toString() {
        return "AnotherBean [myBean=" + myBean + "]";
    }   
}

XML 설정 :

src/main/resources/config/XMLConfig.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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
 
http://www.springframework.org/schema/beans/spring-beans.xsd">
 
    <bean id="myBean" class="com.hmkcode.spring.beans.MyBean">
        <property name="name" value="xmlBean" />
    </bean>
 
    <bean id="anotherBean" class="com.hmkcode.spring.beans.AnotherBean">
                <property name="myBean" ref="myBean" />
        </bean>
</beans>

위의 설정은 아래와 동등하다.

MyBean myBean = new MyBean(); 
myBean.setName("xmlBean");

AnotherBean anotherBean = new AnotherBean();
anotherBean.setMyBean(mybean);

Run:

package com.hmkcode;
 
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
 
import com.hmkcode.spring.beans.AnotherBean;
import com.hmkcode.spring.beans.MyBean;
 
public class App 
{
    public static void main( String[] args )
    {
        ApplicationContext ctxXML = new ClassPathXmlApplicationContext("config/XMLConfig.xml");
        AnotherBean anotherBean = (AnotherBean) ctxXML.getBean("anotherBean");
 
        System.out.println( anotherBean);
    }
}

Output:

AnotherBean [myBean=MyBean [name=xmlBean]]

( 2 ) 어노테이션 기반 설정

Beans + Annotation:

MyBean.java

@Component(value=“myBean2″) : this will enable Spring to detect this bean when scanning and instantiate a bean named “myBean2“
@Value(value=“AnnotationBean”) : this equivalent to mybean2.setName(“AnnotationBean”);

package com.hmkcode.spring.beans;
 
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
 
@Component(value="myBean2")
public class MyBean {
 
    private String name;
 
    public String getName() {
        return name;
    }
 
    @Value(value="AnnotationBean")
    public void setName(String name) {
        this.name = name;
    }
 
    @Override
    public String toString() {
        return "MyBean [name=" + name + "]";
    }
 
}

AnotherBean.java

@Component(value=“anotherBean”) : this will enable Spring to detect this bean when scanning and instantiate a bean named “anotherBean”
@Autowired @Qalifier(“myBean2″): this equivalent to anotherBean.setMyBean(mybean2)

package com.hmkcode.spring.beans;
 
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Component;
 
@Component(value="anotherBean")
public class AnotherBean {
 
    private MyBean myBean;
 
    public MyBean getMyBean() {
        return myBean;
    }
 
    @Autowired
    @Qualifier("myBean2")
    public void setMyBean(MyBean myBean) {
        this.myBean = myBean;
    }
 
    @Override
    public String toString() {
        return "AnotherBean [myBean=" + myBean + "]";
    }
 
}

XML 설정: (annotation 이 사용가능하도록)

단지 어노테이션을 활성화 하기위해 XML 이 필요하다. XML 안에 따로 <bean> 같은 태그를 사용하지 않았다.

XMLConfig-Annotation.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.xsd
            http://www.springframework.org/schema/context
            http://www.springframework.org/schema/context/spring-context.xsd">
      <context:component-scan base-package="com.hmkcode.spring.beans"/>
      <!-- The use of <context:component-scan> implicitly enables the functionality of <context:annotation-config> -->
</beans>

Run:

package com.hmkcode;
 
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.hmkcode.spring.beans.AnotherBean;
 
public class App 
{
    public static void main( String[] args )
    {
 
        ApplicationContext ctxAnnotation = new ClassPathXmlApplicationContext("config/XMLConfig-Annotation.xml");
        AnotherBean anotherBean  = (AnotherBean) ctxAnnotation.getBean("anotherBean");
 
        System.out.println( anotherBean);
 
    }
}

Output:

AnotherBean [myBean=MyBean [name=AnnotationBean]]

( 3 ) 자바를 이용한 설정 (XML 제거됨)

Beans:

MyBean.java

package com.hmkcode.spring.beans;
 
import org.springframework.beans.factory.annotation.Value;
 
public class MyBean {
 
    private String name;
 
    public String getName() {
        return name;
    }
 
    @Value(value="JavaConfigBean")
    public void setName(String name) {
        this.name = name;
    }
 
    @Override
    public String toString() {
        return "MyBean [name=" + name + "]";
    }
 
}

AnotherBean.java

package com.hmkcode.spring.beans;
 
import org.springframework.beans.factory.annotation.Autowired;
 
public class AnotherBean {
 
    private MyBean myBean;
 
    public MyBean getMyBean() {
        return myBean;
    }
 
    @Autowired
    public void setMyBean(MyBean myBean) {
        this.myBean = myBean;
    }
 
    @Override
    public String toString() {
        return "AnotherBean [myBean=" + myBean + "]";
    }
 
}

Cofiguration:

package com.hmkcode.spring.config;
 
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import com.hmkcode.spring.beans.AnotherBean;
import com.hmkcode.spring.beans.MyBean;
 
@Configuration
public class JavaConfig {
 
    @Bean
    public MyBean myBean(){
        return  new MyBean();
    }
 
    @Bean(name = "anotherBean2")
    public AnotherBean anotherBean(){
        return new AnotherBean();
    }
}

Run:

package com.hmkcode;
 
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import com.hmkcode.spring.beans.AnotherBean;
import com.hmkcode.spring.config.JavaConfig;
 
public class App 
{
    public static void main( String[] args )
    {
 
        ApplicationContext ctxJavaConfig = new AnnotationConfigApplicationContext(JavaConfig.class);
        AnotherBean anotherBean = (AnotherBean) ctxJavaConfig.getBean("anotherBean2");
 
        System.out.println( anotherBean);
 
    }
}

Output:

AnotherBean [myBean=MyBean [name=JavaConfigBean]]

위의 코드는 @Configuration 으로 <beans> 를 대신하고
@bean 으로 자바코드에 의한 빈등록을 하게 해주는 예이다.

AnnotationConfigApplicationContext 을 이용하여 설정 클래스를 입력받은후에
getBean 메소드를 통하여 내부의 특정 객체를 가져오는 소스이다.

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