关于Spring自定义XML schema 扩展的问题(Spring面试高频题)

<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:dubbo="http://dubbo.apache.org/schema/dubbo"
       xmlns="http://www.springframework.org/schema/beans"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://dubbo.apache.org/schema/dubbo http://dubbo.apache.org/schema/dubbo/dubbo.xsd">
    <dubbo:application name="demo-provider"/>
    <dubbo:registry address="zookeeper://127.0.0.1:2181"/>
    <dubbo:protocol name="dubbo" port="20890"/>
    <bean id="demoService" class="org.apache.dubbo.samples.basic.impl.DemoServiceImpl"/>
    <dubbo:service interface="org.apache.dubbo.samples.basic.api.DemoService" ref="demoService"/>
</beans>

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
            xmlns:beans="http://www.springframework.org/schema/beans"
            xmlns:tool="http://www.springframework.org/schema/tool"
            xmlns="https://www.javajr.cn/schema/javajr"
            targetNamespace="https://www.javajr.cn/schema/javajr">
 
    <xsd:import namespace="http://www.springframework.org/schema/beans"/>
 
    <xsd:element name="application">
        <xsd:complexType>
            <xsd:complexContent>
                <xsd:extension base="beans:identifiedType">
                    <xsd:attribute name="website" type="xsd:string" use="required"/>
                    <xsd:attribute name="weixin" type="xsd:string" use="required"/>
                </xsd:extension>
            </xsd:complexContent>
        </xsd:complexType>
    </xsd:element>
</xsd:schema>

package org.spring.demo.schema;
import org.springframework.beans.factory.xml.NamespaceHandlerSupport;
public class MyNamespaceHandler extends NamespaceHandlerSupport {
    @Override
    public void init() {
     // 这个名字也不是随便取的，上面编写xsd的根节点元素的name， <xsd:element name="application">
        registerBeanDefinitionParser("application", new MyBeanDefinitionParser());
    }
}

package org.spring.demo.schema;
import org.spring.demo.domain.JavajrDomain;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.xml.AbstractSingleBeanDefinitionParser;
import org.springframework.util.StringUtils;
import org.w3c.dom.Element;
 
public class MyBeanDefinitionParser extends AbstractSingleBeanDefinitionParser {
 
    @Override
    protected Class<?> getBeanClass(Element element) {
        return JavajrDomain.class;
    }
    @Override
    protected void doParse(Element element, BeanDefinitionBuilder bean) {
        // this however is an optional property
        String website = element.getAttribute("website");
        if (StringUtils.hasText(website)) {
            bean.addPropertyValue("website",website);
        }
        String weiXin = element.getAttribute("weixin");
        if (StringUtils.hasText(weiXin)) {
            bean.addPropertyValue("weixin",weiXin);
        }
    }
}

public static void main(String[] args) {
        ApplicationContext ctx = new ClassPathXmlApplicationContext("classpath:applicationContext.xml");
        JavajrDomain bean = ctx.getBean(JavajrDomain.class);
        System.out.println(bean.toString());
    }

JavajrDomain{weixin='javajr8', website='javajr.cn'}