构造器实例化bean

Been1 类

package com.student.instance.constructor;

public class Bean1 {

}

Bean1.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">

	<!-- services -->

	<bean id="bean1" class="com.student.instance.constructor.Bean1">
	</bean>
</beans>

instanceTest1测试类

package com.student.instance.constructor;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class instanceTest1 {

	public static void main(String[] args) {
		String xmlPath = "com/student/instance/constructor/Bean1.xml";
		ApplicationContext applicationContext =new ClassPathXmlApplicationContext(xmlPath);
		Bean1 bean =(Bean1)applicationContext.getBean("bean1");
		System.out.println(bean);

	}

}

解释：在加载配置文件的时候，Spring容器（ApplicationContext）会通过Bean1(实现类)或者说被调用的类的无参构造方法，对Bean进行实例化。也就是说，加载配置文件的同时，被调用的类通过自己的无参构造方法，把自己交给了Bean（Spring容器）。

运行结果：

十月 13, 2019 2:11:44 下午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@46f7f36a: startup date [Sun Oct 13 14:11:44 CST 2019]; root of context hierarchy
十月 13, 2019 2:11:44 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [com/student/instance/constructor/Bean1.xml]
com.student.instance.constructor.Bean1@6a024a67