<custom:bean class="com.lcl.spring.beans.CustomBean"></custom:bean>

package com.lcl.spring.beans;

public class CustomBean {
    public void sayHi(){
        System.out.println("Hello Custom NamespaceHandler");
    }
}

package com.lcl.spring.ext;

import org.springframework.beans.factory.xml.NamespaceHandlerSupport;

/**
 * 自定義命名空間解析器
 */
public class CustomNamespaceHandler extends NamespaceHandlerSupport {

    @Override
    public void init() {
        // 在初始化方法中，注入標簽解析器，此時我們需要解析<custom:bean/>
        registerBeanDefinitionParser("bean", new CustomBeanDefinitionParser());
        // 注入其他解析器...
    }
}

package com.lcl.spring.ext;

import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.BeanDefinitionHolder;
import org.springframework.beans.factory.support.BeanDefinitionReaderUtils;
import org.springframework.beans.factory.xml.BeanDefinitionParser;
import org.springframework.beans.factory.xml.ParserContext;
import org.w3c.dom.Element;

/**
 * 自定義解析器
 */
public class CustomBeanDefinitionParser implements BeanDefinitionParser {

    @Override
    public BeanDefinition parse(Element element, ParserContext parserContext) {
        // 為了演示方便起見，使用BeanDefinitionParserDelegate解析bean definition
        BeanDefinitionHolder beanDefinitionHolder = parserContext.getDelegate().parseBeanDefinitionElement(element);
        // 使用工具類注冊
        BeanDefinitionReaderUtils.registerBeanDefinition(beanDefinitionHolder, parserContext.getRegistry());
        // 或是使用注冊器注冊
        //parserContext.getRegistry().registerBeanDefinition(beanDefinitionHolder.getBeanName(),beanDefinitionHolder.getBeanDefinition());
        return beanDefinitionHolder.getBeanDefinition();
    }
}

<?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:custom="http://www.lcl.com/schema/custom"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
            http://www.lcl.com/schema/custom http://www.lcl.com/schema/custom.xsd">
    <custom:bean class="com.lcl.spring.beans.CustomBean"></custom:bean>
</beans>

package com.lcl.spring;

import com.lcl.spring.beans.CustomBean;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringCustomNamespaceHandlerDemo {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("context.xml");
        CustomBean bean = applicationContext.getBean(CustomBean.class);
        bean.sayHi();
    }
}