Spring 由构造函数自动装配，通过构造函数的参数与配置文件中的 beans 名称进行匹配和连接，匹配成功，注入 bean ，否则，抛出异常
    案例代码：
    Person.java

    1. package com.baklib.custom;
    3. public class Person {
    5.     private String name;
    6.     private int age;
    8.     public Person(String name, int age) {
    9.         this.name = name;
    10.         this.age = age;
    11.     }
    13.     public String getName() {
    14.         return name;
    15.     }
    17.     public int getAge() {
    18.         return age;
    19.     }
    20. }

    Car.java

    1. package com.baklib.custom;
    3. public class Car {
    5.     private String name;
    6.     private double price;
    8.     public Car(String name, double price) {
    9.         this.name = name;
    10.         this.price = price;
    11.     }
    13.     public String getName() {
    14.         return name;
    15.     }
    17.     public double getPrice() {
    18.         return price;
    19.     }
    20. }

    Action.java

    1. package com.baklib.custom;
    3. public class Action {
    5.     private Person person;
    6.     private Car car;
    8.     public Action(Person person, Car car) {
    9.         this.person = person;
    10.         this.car = car;
    11.     }
    13.     public Person getPerson() {
    14.         return person;
    15.     }
    17.     public Car getCar() {
    18.         return car;
    19.     }
    21.     public void buyCar() {
    22.         System.out.println(person.getName()+"今年"+person.getAge()+"岁，花了"
    23.                 +car.getPrice()+"元买了"+car.getName());
    24.     }
    25. }

    MainApp.java

    1. package com.baklib.custom;
    3. import org.springframework.context.ApplicationContext;
    4. import org.springframework.context.support.ClassPathXmlApplicationContext;
    6. public class MainApp {
    8.     public static void main(String[] args) {
    9.         ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");
    11.         Action action = (Action) context.getBean("action");
    12.         action.buyCar();
    13.     }
    15. }

    配置文件 Beans.xml

    1. <?xml version="1.0" encoding="UTF-8"?>
    2. <beans xmlns="http://www.springframework.org/schema/beans"
    3.        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    4.        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    6.     <bean id="action" class="com.baklib.custom.Action" autowire="constructor">
    7.     </bean>
    9.     <bean id="car" class="com.baklib.custom.Car">
    10.         <constructor-arg name="name" value="小轿车"/>
    11.         <constructor-arg name="price" value="100000"/>
    12.     </bean>
    14.     <bean id="person" class="com.baklib.custom.Person">
    15.         <constructor-arg name="name" value="张三"/>
    16.         <constructor-arg name="age" value="20"/>
    17.     </bean>
    19. </beans>

    编写完以上代码，就可以运行这个程序，运行结束后，可以在控制台看到下面的信息

    1. 张三今年20岁，花了100000.0元买了小轿车