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());
    }
}