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() {
    }
    
    @Override
    public InterfaceUserDao getObject() throws Exception {
        System.out.println("继承接口FactoryBean");
        
        return new UserDaoImpl();
    }
    
    @Override
    public Class<?> getObjectType() {
        return null;
    }
    
    @Override
    public 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.xsd
       http://www.springframework.org/schema/context 
       http://www.springframework.org/schema/context/spring-context-4.0.xsd
       http://www.springframework.org/schema/tx 
       http://www.springframework.org/schema/tx/spring-tx-4.0.xsd
       http://www.springframework.org/schema/aop
       http://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 {
    
    @Test
    public 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();
    }
}