spring in action 学习十二：property placeholder 注解的方式实现避免注入外部属性硬代码化

这里的注解是指@PropertySource这个注解。用@PropertySource这个注解加载.properties文件。

案例的目录结构如下：

student.properties的代码如下：

 #用配置文件的形式，避免注入属性值的硬代码化。
 name=AbrahamLincoln
 age=21

Student的代码如下：

 package com.advancedWiring.ambiguityIniAutowiring2;

 import org.springframework.beans.factory.BeanNameAware;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.beans.factory.config.ConfigurableBeanFactory;
 import org.springframework.context.annotation.Scope;
 import org.springframework.context.annotation.ScopedProxyMode;
 import org.springframework.stereotype.Component;
 import org.springframework.web.context.WebApplicationContext;

 /**
  * Created by ${秦林森} on 2017/6/9.
  */
 @Component
 public class Student implements BeanNameAware{
     private  String name;
     private Integer age;

     public String getName() {
         return name;
     }
     @Value("${name}")//注入值
     public void setName(String name) {
         this.name = name;
     }

     public Integer getAge() {
         return age;
     }
     @Value("${age}")//注入值
     public void setAge(Integer age) {
         this.age = age;
     }

     @Override
     public void setBeanName(String name) {
         System.out.println("the Student bean name is :"+name);
     }

     /**
      * write this constructor mainly to inject external property value.
      * @param name the student's name
      * @param age  the student's age
      */
     public Student(  String name,   Integer age) {
         this.name = name;
         this.age = age;
     }

     public Student() {
     }
 }

StudentConfig的代码如下：

 package com.advancedWiring.ambiguityIniAutowiring2;

 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.config.ConfigurableBeanFactory;
 import org.springframework.context.annotation.*;
 import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
 import org.springframework.core.env.Environment;

 /**
  * Created by ${秦林森} on 2017/6/9.
  */
 @Configuration
 /**
  * @PropertySource主要是加载.properties文件。
  */
 @ComponentScan
 @PropertySource("classpath:com/advancedWiring/ambiguityIniAutowiring2/student.properties")
 public class StudentConfig {

 }

测试类的代码如下：

 package com.advancedWiring.ambiguityIniAutowiring2;

 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.support.ClassPathXmlApplicationContext;
 import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;

 /**
  * Created by ${秦林森} on 2017/6/9.
  */
 public class Test {
     public static void main(String[] args) {

         AnnotationConfigApplicationContext ac = new AnnotationConfigApplicationContext(StudentConfig.class);
         Student student = ac.getBean(Student.class);
         /**
          * 输出结果是：the student name is: AbrahamLincoln and age is :21
          * 可以看出他把配置文件的值给取出来了。
          */
         System.out.println("the student name is: "+student.getName()+" and age is :"+student.getAge());
     }
 }