Spring, Dependency Injection 종류 생성자주입, 수정자주입, 필드주입

생성자 주입

annotation

MsgProvider.java

package constructor.annotation;

import org.springframework.stereotype.Component;

@Component("provider")
public class MsgProvider {
    private String msg = "Hello World!(Constructor Injection annotation)";

    public String getMsg() {
        return msg;
    }
}

MsgRender.java

package constructor.annotation;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service("render")
public class MsgRender {
    private MsgProvider msgProvider;

    @Autowired
    public MsgRender(MsgProvider msgProvider) {
        this.msgProvider = msgProvider;
    }

    public void render() {
        System.out.println(msgProvider.getMsg());
    }
}

ConstructorConfig.java

package constructor.annotation;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@ComponentScan
@Configuration
public class ConstructorConfig {
}

Main.java

package constructor.annotation;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class Main {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(ConstructorConfig.class);
        MsgRender msgRender = ctx.getBean("render", MsgRender.class);
        msgRender.render();
    }
}

xml

MsgProvider.java

package constructor.xml;

public class MsgProvider {
    private String msg = "Hello World!(Constructor Injection xml)";

    public String getMsg() {
        return msg;
    }
}

MsgRender.java

package constructor.xml;

public class MsgRender {
    private MsgProvider msgProvider;

    public MsgRender(MsgProvider msgProvider) {
        this.msgProvider = msgProvider;
    }

    public void render() {
        System.out.println(msgProvider.getMsg());
    }
}

constructor-config.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="provider"
          class="constructor.xml.MsgProvider">
    </bean>

    <bean id="render"
          class="constructor.xml.MsgRender">
        <constructor-arg ref="provider"/>
    </bean>
</beans>

Main.java

package constructor.xml;

import org.springframework.context.support.GenericXmlApplicationContext;

public class Main {
    public static void main(String[] args) {
        GenericXmlApplicationContext ctx = new GenericXmlApplicationContext("classpath:constructor-config.xml");
        MsgRender msgRender = ctx.getBean("render", MsgRender.class);
        msgRender.render();
    }
}

수정자 주입

annotation

MsgProvider.java

package setter.annotation;

import org.springframework.stereotype.Component;

@Component("provider")
public class MsgProvider {
    private String msg = "Hello World!(Setter Injection annotation)";

    public String getMsg() {
        return msg;
    }
}

MsgRender.java

package setter.annotation;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service("render")
public class MsgRender {
    private MsgProvider msgProvider;

    @Autowired
    public void setMsgProvider(MsgProvider msgProvider) {
        this.msgProvider = msgProvider;
    }

    public void render() {
        System.out.println(msgProvider.getMsg());
    }
}

SetterConfig.java

package setter.annotation;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@ComponentScan
@Configuration
public class SetterConfig {
}

Main.java

package setter.annotation;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class Main {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(SetterConfig.class);
        MsgRender render = ctx.getBean("render", MsgRender.class);
        render.render();
    }
}

xml

MsgProvider.java

package setter.xml;

public class MsgProvider {
    private String msg = "Hello World!(Setter Injection xml)";

    public String getMsg() {
        return msg;
    }
}

MsgRender.java

package setter.xml;

public class MsgRender {
    private MsgProvider msgProvider;

    public void setMsgProvider(MsgProvider msgProvider) {
        this.msgProvider = msgProvider;
    }

    public void render() {
        System.out.println(msgProvider.getMsg());
    }
}

setter-config.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:p="http://www.springframework.org/schema/p"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
                           http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="provider"
          class="setter.xml.MsgProvider"/>


    <bean id="render"
          class="setter.xml.MsgRender"
          p:msgProvider-ref="provider">
    </bean>

    <bean id="render_property"
          class="setter.xml.MsgRender">
        <property name="msgProvider" ref="provider"/>
    </bean>

</beans>

Main.java

package setter.xml;

import org.springframework.context.support.GenericXmlApplicationContext;

public class Main {
    public static void main(String[] args) {
        GenericXmlApplicationContext ctx = new GenericXmlApplicationContext("classpath:setter-config.xml");
        MsgRender msgRender = ctx.getBean("render", MsgRender.class);
        msgRender.render();

        MsgRender msgRender2 = ctx.getBean("render_property", MsgRender.class);
        msgRender2.render();
    }
}

필드 주입

annotation

MsgProvider.java

package field.annotation;

import org.springframework.stereotype.Component;

@Component("provider")
public class MsgProvider {
    private String msg = "Hello World!(Field Injection annotation)";

    public String getMsg() {
        return msg;
    }
}

MsgRender.java

package field.annotation;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service("render")
public class MsgRender {
    @Autowired
    private MsgProvider msgProvider;

    public void render() {
        System.out.println(msgProvider.getMsg());
    }
}

FieldConfig.java

package field.annotation;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@ComponentScan
@Configuration
public class FieldConfig {
}

Main.java

package field.annotation;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class Main {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(FieldConfig.class);
        MsgRender msgRender = ctx.getBean("render", MsgRender.class);
        msgRender.render();
    }
}