2、Spring4之Bean的两种配置方式

1. Bean 属性的配置方式

     1）. setter 方法注入（最常用的方式）

          ①. 在 Bean 中为属性提供 setter 方法：

          public void setBrand(String brand) {
               this.brand = brand;
          }

          public void setCorp(String corp) {
               this.corp = corp;
          }

          public void setPrice(float price) {
               this.price = price;
          }

          public void setMaxSpeed(int maxSpeed) {
               this.maxSpeed = maxSpeed;
          }

        ②. 在配置文件中使用 property 注入属性值

          <bean id="car" class="com.atguigu.spring.ioc.Car">
               <property name="brand" value="Audi"></property>
               <property name="corp" value="一汽"></property>
               <property name="maxSpeed" value="200"></property>
               <property name="price" value="200000"></property>
          </bean>

     2）. 构造器注入：

          ①. bean 中提供构造器：

          public Car(String brand, String corp, int price, int maxSpeed) {
               super();
               this.brand = brand;
               this.corp = corp;
               this.price = price;
               this.maxSpeed = maxSpeed;
          }

          public Car(String brand, String corp, float price) {
               super();
               this.brand = brand;
               this.corp = corp;
               this.price = price;
          }

          public Car(String brand, String corp, int maxSpeed) {
               super();
               this.brand = brand;
               this.corp = corp;
               this.maxSpeed = maxSpeed;
          }

          ②. 配置文件中使用 constructor-arg 节点配置使用构造器注入属性值

          <bean id="car2" class="com.atguigu.spring.ioc.Car">
               <constructor-arg value="Ford"></constructor-arg>
               <constructor-arg value="ChangAn"></constructor-arg>
               <constructor-arg value="250000"></constructor-arg>
               <constructor-arg value="190"/>
          </bean>

          ③. 注意：对于重载的构造器可以通过参数的类型来匹配对应的构造器


          <bean id="car3" class="com.atguigu.spring.ioc.Car">
               <constructor-arg value="Buike"></constructor-arg>
               <constructor-arg value="ShanghaiTongYong"></constructor-arg>
               <constructor-arg value="180000"></constructor-arg>
          </bean>

          <!-- 
               因为有重载的构造器:
               public Car(String brand, String corp, float price)
               public Car(String brand, String corp, int maxSpeed)
        所以必须指定使用哪一个构造器来初始化属性值. 可以使用构造器参数的类型来选择需要的构造器!
          -->

          解决办法：
          <bean id="car4" class="com.atguigu.spring.ioc.Car">
               <constructor-arg value="Nissan"></constructor-arg>
               <constructor-arg value="Zhengzhou"></constructor-arg>
               <constructor-arg value="210" type="int"></constructor-arg>
          </bean>