Spring will invoke specific constructor no matter this constructor is public or private-优快云博客

本文链接：https://blog.youkuaiyun.com/lsm135/article/details/53456773

本文通过一个具体的案例，展示了Spring框架如何在初始化Bean时调用构造器，并证实了无论构造器是否为公共访问级别，Spring都会进行调用。此外，文章还探讨了使用Spring结合工厂模式实例化对象的方法。

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I have confirm this conclusion via debugging my own code.

Spring will invoke specific constructor no matter this constructor is public or private

This is my demo:

package com.frank.zk;

/**
 * 
 * @author liushaomingdev@163.com
 *
 */
public class ZooKeeperManager extends ZookeeperClient implements Watcher {
	private static ZooKeeperManager INSTANCE;
	private ZooKeeperManager() {
		INSTANCE = this;
	}
	public static ZooKeeperManager getInstance() {
		return INSTANCE;
	}
}

this is configuration file--applicationContext.xml

<?xml version="1.0" encoding="utf-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:util="http://www.springframework.org/schema/util" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:context="http://www.springframework.org/schema/context" xmlns:tx="http://www.springframework.org/schema/tx"
	xmlns:aop="http://www.springframework.org/schema/aop"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.1.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.1.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.1.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.1.xsd">
	<bean id="zookeeper" class="com.frank.zk.ZooKeeperManager" lazy-init="false" />
</beans>

Program execute to this break point finally.

private ZooKeeperManager() {
	INSTANCE = this;
}

So, below conclusion is confirmed:
Spring will invoke specific constructor no matter this constructor is public or private

This program use Spring to initialize singleton creating bean. It also uses Factory pattern to instantiate object.

Demo code

// bean 'ZooKeeperManager' is registered as singleton bean in Spring Container after this line code.
ApplicationContext appContext = new ClassPathXmlApplicationContext("appContext.xml");

ZooKeeperManager manager = ZooKeeperManager.getInstance();