spring：继承接口FactoryBean获取bean实例

spring框架提供接口FactoryBean获取bean实例。

实现步骤：

实现接口FactoryBean。

在xml文件中配置实现接口FactoryBean的类。

调用接口FactoryBean中方法getObject，获取bean实例。

 实现接口类

package com.itheima.factory;import org.springframework.beans.factory.FactoryBean;import com.itheima.dao.interfaces.InterfaceUserDao;
import com.itheima.dao.impl.UserDaoImpl;/*** @copyright 2003-2024* @author    qiao wei* @date      2024-12-24* @version   1.0* @brief     继承接口FactoryBean。通过方法getBean获取Bean，时是延迟调用。* @history   name*            date*            brief*/
public class MyBeanFactory03 implements FactoryBean<InterfaceUserDao> {public MyBeanFactory03() {}@Overridepublic InterfaceUserDao getObject() throws Exception {System.out.println("继承接口FactoryBean");return new UserDaoImpl();}@Overridepublic Class<?> getObjectType() {return null;}@Overridepublic boolean isSingleton() {return FactoryBean.super.isSingleton();}
}

xml配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:p="http://www.springframework.org/schema/p"xmlns:context="http://www.springframework.org/schema/context"xmlns:aop="http://www.springframework.org/schema/aop"xmlns:tx="http://www.springframework.org/schema/tx"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsdhttp://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsdhttp://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsdhttp://www.springframework.org/schema/aophttp://www.springframework.org/schema/aop/spring-aop-4.0.xsd"><!--  --><bean id="myUserDao03"class="com.itheima.factory.MyBeanFactory03"></bean>
</beans>

测试调用

package com.itheima.factory;import org.junit.jupiter.api.Test;
import org.springframework.context.support.ClassPathXmlApplicationContext;import com.itheima.dao.interfaces.InterfaceUserDao;/*** @copyright 2003-2025* @author    qiao wei* @date      2025-04-05* @version   1.0* @brief     继承接口FactoryBean。在读取配置文件时不创建Bean实例。在调用方法getBean时才创建Bean实例并返回。* @history   name*            date*            brief*/
class MyBeanFactory03Test {@Testpublic void test01() {// 读取配置文件，创建容器，未创建Bean实例。ClassPathXmlApplicationContext context =new ClassPathXmlApplicationContext("/xml/factory/myBeanFactory03.xml");// 通过方法getBean获取Bean实例时，才创建Bean实例。InterfaceUserDao userDao = (InterfaceUserDao) context.getBean("myUserDao03");userDao.print();}
}