Spring中的@Value和@PropertySource注解详解

@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();
}

@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;
}

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component
public class Person {
    /**
     * @Value赋值方式1：基本数值
     */
    @Value("张三")
    private String name;
    /**
     * @Value赋值方式2：SpEl表达式  #{}
     */
    @Value("#{ 20-2 }")
    private int age;
    /**
     * @Value赋值方式3：${},读取配置文件[xxx.properties]中的值
     */
    @Value("${person.phone}")
    private String phone;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getPhone() {
        return phone;
    }
    public void setPhone(String phone) {
        this.phone = phone;
    }
    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", phone='" + phone + '\'' +
                '}';
    }
}

import org.springframework.context.annotation.*;

/**
 * 使用@PropertySource注解可以读取外部配置文件中的key-value保存到运行的环境变量中
 */
@PropertySource(value = {"classpath:/person.properties"},encoding = "UTF-8")
@ComponentScan({"com.dashu"})
@Configuration
public class BeanConfig {
}

person.phone = 11111111

import com.dashu.bean.Person;
import com.dashu.config.BeanConfig;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.core.env.ConfigurableEnvironment;
public class Main {
    public static void main(String[] args) {
        //加载配置类获取容器
        AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(BeanConfig.class);
        //容器中获取Person
        Person person = annotationConfigApplicationContext.getBean(Person.class);
        //打印
        System.out.println(person);
        System.out.println("--------------------");
        /**
         * 获取运行时环境实例
         */
        ConfigurableEnvironment environment = annotationConfigApplicationContext.getEnvironment();
        /**
         * 根据外部文件的key，从环境中获取value
         */
        String property = environment.getProperty("person.phone");
        //打印
        System.out.println(property);
    }
}