(九) spring 使用自定义限定符注解

案例一

• 定义接口  CD.java

package interfacepackage;

public interface CD {
    void play();
}

• 定义接口 player .java

package interfacepackage;

//定义一个播放器接口
public interface player {
    void play();
}

• 定义接口的实现类   CD1.java

package bean;

import org.springframework.stereotype.Component;

import annotation_self.CD1_Annotation;
import annotation_self.CD_Annotation;
import interfacepackage.CD;
@Component
@CD_Annotation    //使用自定义限定符来标识这个bean，类似于bean的id
@CD1_Annotation //使用自定义限定符来标识这个bean，类似于bean的id
public class CD1  implements CD{

    @Override
    public void play() {
        System.out.println("我是 CD1");
        
    }
    
}

• 定义接口的实现类   CD2.java

package bean;

import org.springframework.stereotype.Component;

import annotation_self.CD2_Annotation;
import annotation_self.CD_Annotation;
import interfacepackage.CD;
@Component
@CD_Annotation  //使用自定义限定符来标识这个bean，类似于bean的id属性
@CD2_Annotation //使用自定义限定符来标识这个bean，类似于bean的id属性
public class CD2  implements CD{

    @Override
    public void play() {
        System.out.println("我是 CD2");
        
    }
    
}

• 定义接口的实现类 CDPlayer.java

package bean;

import interfacepackage.CD;
import interfacepackage.player;

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

import annotation_self.CD2_Annotation;
import annotation_self.CD_Annotation;

@Component("cdp")
public class CDPlayer implements player {

    @Autowired
    @CD_Annotation  
    @CD2_Annotation  //表示注入的bean的限定符必须有@CD_Annotation和@CD2_Annotation
    private CD cd;

    @Override
    public void play() {

        cd.play();
    }

}

• 定义配置类 CDPlayerConfig.java

package config;

import interfacepackage.CD;

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

import bean.CDPlayer;

@Configuration
@ComponentScan(basePackages="bean")
public class CDPlayerConfig {

}

• 自定义注解限定符  CD_Annotation .java

package annotation_self;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

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

@Target({ElementType.CONSTRUCTOR,ElementType.FIELD,ElementType.METHOD,ElementType.TYPE})  //该自定义注解限定符的作用目标
@Retention(RetentionPolicy.RUNTIME)
@Qualifier   //说明这是个自定义限定符
public @interface CD_Annotation {

}

• 自定义注解限定符  CD1_Annotation .java

package annotation_self;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

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

@Target({ElementType.CONSTRUCTOR,ElementType.FIELD,ElementType.METHOD,ElementType.TYPE})  //该自定义注解限定符的作用目标
@Retention(RetentionPolicy.RUNTIME)
@Qualifier   //说明这是个自定义限定符
public @interface CD1_Annotation {

}

• 自定义注解限定符  CD2_Annotation .java

package annotation_self;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

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

@Target({ElementType.CONSTRUCTOR,ElementType.FIELD,ElementType.METHOD,ElementType.TYPE})  //该自定义注解限定符的作用目标
@Retention(RetentionPolicy.RUNTIME)
@Qualifier  //说明这是个自定义限定符
public @interface CD2_Annotation {

}

• 编写测试类 Test.java

package test;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import config.CDPlayerConfig;
import bean.CDPlayer;

public class Test {
    public static void main(String[] args) {
        
        ApplicationContext context=new AnnotationConfigApplicationContext(CDPlayerConfig.class);
        CDPlayer cdplayer=(CDPlayer)context.getBean("cdp");
        cdplayer.play();
        
        
    }
}

结果：