浅谈springioc实例化bean的三个方法

public class HelloWorld {
   
  public HelloWorld(){
    System.out.println("aaaa");
  }
   
  public void hello(){
    System.out.println("hello world");
  }
}

public class HelloWorldFactory {
  public static HelloWorld getInstance(){
    return new HelloWorld();
  }
}

<?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-2.5.xsd">
  <!--
    在这个配置中，spring容器要用默认的构造函数为HelloWorld创建对象
   -->
  <bean id="helloWorld" class="HelloWorld"></bean>
   
  <!--
    采用静态工厂方法创建对象
      factory-method为工厂方法
   -->
   <bean id="helloWorld2" class="HelloWorldFactory" factory-method="getInstance"></bean>
</beans>

@Test
  public void test(){
    ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
    HelloWorld world = (HelloWorld)context.getBean("helloWorld2");
    world.hello();
  }