==================
Spring工厂底层原理
==================

 __________________________________________________________________
|<bean id="student" class="cn.tedu.hellospring.Student"/>          |
|__________________________________________________________________|
                                  |读取配置文件
                                  v
 __________________________________________________________________
|ApplicationContext applicationContext =                           |
|    new ClassPathXmlApplicationContext("/applicationContext.xml");|
|__________________________________________________________________|
                                  |构建id-class映射表
                                  v
 __________________________________________________________________ 
|                id               |              class             |
|---------------------------------|--------------------------------|
|             student             |   cn.tedu.hellospring.Student  |
|               ...               |                ...             |
|_________________________________|________________________________|
                                  |利用反射创建Bean对象
                                  v
 __________________________________________________________________
|public class Student {                                            |
|    ...                                                           |
|}                                                                 |
|__________________________________________________________________|
                                  |获取Bean对象
                                  v
 __________________________________________________________________
|Student student = (Student) applicationContext.getBean("student");|
|__________________________________________________________________|
                                  |使用Bean对象
                                  v
 __________________________________________________________________
|                                ...                               |
|__________________________________________________________________|

Spring工厂在利用反射创建对象的过程中，会调用相应类的无参构造方法，即使该方法被声明为私有。

/src/main/java/cn/tedu/hellospring/Student.java：

public class Student {
    /*public*/private Student() {
        System.out.println("Student.Student");
    }
}

Student.Student
cn.tedu.hellospring.Student@47eaca72