【3】IOC创建对象的方式

4、IOC创建对象的方式

4.1、通过无参构造方法来创建

1. Teacher.java

   public class Teacher {
       private String name;
   
       public Teacher() {
           System.out.println("Teacher对象默认被创建");
       }
   
       public String getName() {
           return name;
       }
   
       public void setName(String name) {
           this.name = name;
       }
   
       public void show(){
           System.out.println("name="+name);
       }
   }
   

2. beans.xml

   <?xml version="1.0" encoding="UTF-8"?>
   <beans xmlns="http://www.springframework.org/schema/beans"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://www.springframework.org/schema/beans
          http://www.springframework.org/schema/beans/spring-beans.xsd">
   
       <bean id="teacher" class="com.kuber.pojo.Teacher" name="teacher2">
       	<property name="name" value="工藤静香真好看"/>
       </bean>
   
   </beans>
   

3. 测试类

   @Test
   public void test1(){
       ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
       Teacher teacher = (Teacher) context.getBean("teacher2");
       teacher.show();
   }
   

4. 输出效果

4.2、通过有参方法来构造

1. User.java

   public class User {
       private String name;
   
       public User(String name) {
           this.name = name;
       }
   
       public String getName() {
           return name;
       }
   
       public void setName(String name) {
           this.name = name;
       }
   
       public void show(){
           System.out.println("name="+name);
       }
   }
   

2. beans.xml

   <?xml version="1.0" encoding="UTF-8"?>
   <beans xmlns="http://www.springframework.org/schema/beans"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://www.springframework.org/schema/beans
           https://www.springframework.org/schema/beans/spring-beans.xsd">
       <bean id="user" class="com.kuber.pojo.User">
           <!--<constructor-arg index="0" value="工藤静香"/>-->
           <constructor-arg name="name" value="工藤静香"/>
       </bean>
   
   </beans>
   

   其中constructor-arg有三种配置方式

   <!-- 第一种根据index参数下标设置 -->
   <bean id="user" class="com.kuang.pojo.User">
      <!-- index指构造方法 , 下标从0开始 -->
      <constructor-arg index="0" value="工藤静香"/>
   </bean>
   <!-- 第二种根据参数名字设置 -->
   <bean id="user" class="com.kuang.pojo.User">
      <!-- name指参数名 -->
      <constructor-arg name="name" value="工藤静香"/>
   </bean>
   <!-- 第三种根据参数类型设置 -->
   <bean id="user" class="com.kuang.pojo.User">
      <constructor-arg type="java.lang.String" value="工藤静香"/>
   </bean>
   

3. 测试

   @Test
   public void test1(){
       ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
       User user = context.getBean("user", User.class);
       user.show();
   }
   

4. 结果

   

结论：在配置文件加载的时候，其中管理的对象都已经开始初始化了。