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@Target({ElementType.FIELD, ElementType.METHOD, ElementType.PARAMETER, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Value {

   /**
    * The actual value expression such as <code>#{systemProperties.myProp}</code>
    * or property placeholder such as <code>${my.app.myProp}</code>.
    */
   String value();

}

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package com.eh.bean;

import lombok.Data;
import org.springframework.beans.factory.annotation.Value;

@Data
public class Person {
    //使用@Value赋值
    //1、基本数值
    //2、可以写SpEL； #{}
    //3、可以写${}；取出配置文件【properties】中的值（properties中的值会放在运行环境变量里面）,需要结合注解@PropertySource一起使用，当然在配置文件中引入context-placeholder也是可以的

    @Value("张三")
    private String name;
    @Value("#{20-2}")
    private Integer age;

    @Value("${person.nickName}")
    private String nickName;
}

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@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Repeatable(PropertySources.class)
public @interface PropertySource {
   String name() default "";

   String[] value();

   boolean ignoreResourceNotFound() default false;

   String encoding() default "";

   Class<? extends PropertySourceFactory> factory() default PropertySourceFactory.class;

}

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package com.atguigu.config;

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

import com.atguigu.bean.Person;

//使用@PropertySource读取外部配置文件中的k/v保存到运行的环境变量中;加载完外部的配置文件以后使用${}取出配置文件的值
@PropertySource(value={"classpath:/person.properties"})
@Configuration
public class MainConfigOfPropertyValues {
   
   @Bean
   public Person person(){
      return new Person();
   }

}

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ConfigurableEnvironment environment = applicationContext.getEnvironment();
String property = environment.getProperty("person.nickName");
System.out.println(property);