spring中@Configuration的重要性

代码：
test.properties

book.name=java
book.author=jolie

ELConfig.java

package com.yubai.EL;

import org.apache.commons.io.IOUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.core.env.Environment;
import org.springframework.core.io.Resource;


//@Configuration
@PropertySource("classpath:com/yubai/EL/test.properties")
public class ELConfig {

    @Autowired
    private Environment environment;

   public void output(){
        try{
          System.out.println(environment.getProperty("book.author"));
        }catch (Exception e){
            e.printStackTrace();
        }
   }
}

Main.java

package com.yubai.EL;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class MainEl {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(ELConfig.class);
        ELConfig resource = context.getBean(ELConfig.class);
        resource.output();
        context.close();
    }
}

当把ELConfig.java中类前的@Configuration注释掉后environment.getProperty(“book.author”)获得的值是null

？？？

不知道为什么注释@Configuration后从test.properties中获取的值是null，之后抽时间学习debug调试