spring 自定义标签实现

Spring 自定义标签实现

参考资料:
dubbo对spring自定义标签的扩展的实现:https://my.oschina.net/lenglingx/blog/889662

一、自定义Spring标签简介

Spring官方文档 42.1中,介绍了如何自定义Spring标签,步骤如下:
1、编写一个XML Schema描述您的自定义元素
2、编写自定义命名空间处理程序实现,实现NamespackHandler接口
3、编写一个或多个自定义的Bean定义解析器,实现BeanDefinitionParser接口
4、注册到Spring容器

ps:官方文档描述出处,打开 https://docs.spring.io/spring/docs/4.3.20.BUILD-SNAPSHOT/spring-framework-reference/htmlsingle/#extensible-xml-introduction ,搜索42.1即可

二、自定义标签实现

1、编写yf.xsd,名称根据自己的喜好来写即可
complexContent 该复杂类型只包含元素或不包含任何元素内容(空)
attribute 该复杂类型包含指定的属性。
annotation和documentation,结合起来,对定义的内容,做一定的文字说明

<xsd:annotation>
    <xsd:documentation>
        xsd:documentation>
xsd:annotation>

1)定义一个type


<xsd:complexType name="applicationType">
    
    <xsd:attribute name="id" type="xsd:ID">
        <xsd:annotation>
            <xsd:documentation>xsd:documentation>
        xsd:annotation>
    xsd:attribute>
xsd:complexType>

2)定义标签,并指定其引用哪个type,截取部分示例如下


<xsd:element name="application" type="applicationType">
    <xsd:annotation>
        <xsd:documentation>xsd:documentation>
    xsd:annotation>
xsd:element>

3)编写标签对应的实体类。(一个标签对应一个实体类)
两个标签:applaction、registry,实体类对应Application、Registry

2、编写标签解析类(因为命名空间中需要用到此类)

ApplicationBeanDefinitionParser.java
RegistryBeanDefinitionParser.java

3、编写命名空间处理类

public class YfNamespaceHandler extends NamespaceHandlerSupport {
    @Override
    public void init() {
        /**
         * registerBeanDefinitionDecorator(String elementName, BeanDefinitionDecorator dec)
         * 通过指定的BeandefiniParser解析xsd中定义的element元素
         */
        registerBeanDefinitionParser("application", new ApplicationBeanDefinitionParser(Application.class, true));
        registerBeanDefinitionParser("registry", new RegistryBeanDefinitionParser());
    }
}

4、编写spring.handlers和spring.schemas串联起所有部件,二者都存放在META-INF文件夹下

spring.handlers指定NamespaceHandler,内容如下:

http\://yf.oschina.net/schema/yf= com.yf.springcustomtag.springsupport.YfNamespaceHandler

spring.schemas解析XML文件时将xsd文件重定向到本地文件,避免从网上下载xsd文件(通过实现org.xml.sax.EntityResolver接口来实现该功能),内容如下:

http\://yf.oschina.net/schema/yf.xsd=META-INF/yf.xsd

5、测试

1)编写spring配置applicationContext.xml,注意Beans中引入自定义标签的xmlns信息

xmlns:yf="http://yf.oschina.net/schema/yf"
http://yf.oschina.net/schema/yf http://yf.oschina.net/schema/yf.xsd

完整内容如下:


<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:c="http://www.springframework.org/schema/c"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:lang="http://www.springframework.org/schema/lang"
       xmlns:util="http://www.springframework.org/schema/util"
       xmlns:yf="http://yf.oschina.net/schema/yf"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
      http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd
      http://www.springframework.org/schema/lang http://www.springframework.org/schema/lang/spring-lang-3.2.xsd
      http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.2.xsd

      http://yf.oschina.net/schema/yf http://yf.oschina.net/schema/yf.xsd">
    

    <yf:application id="applicationTest"  name="yfNameTest" version="1.0" />
    <yf:registry id="yfRegistry" address="127.0.0.1" port="8080" />
beans>

2)编写测试类

public class YfTagTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");

        Application application1 = (Application) context.getBean("applicationTest");
        System.out.println(application1.toString());

        Registry registry1 =  (Registry) context.getBean("yfRegistry");
        System.out.println(registry1.toString());

    }
}

3)运行测试类,结果如下,表明自定义标签测试成功。

23:34:29.734 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Returning cached instance of singleton bean 'lifecycleProcessor'
23:34:29.743 [main] DEBUG org.springframework.core.env.PropertySourcesPropertyResolver - Could not find key 'spring.liveBeansView.mbeanDomain' in any property source
23:34:29.752 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Returning cached instance of singleton bean 'applicationTest'
Application{id='applicationTest', name='yfNameTest', version='1.0'}
23:34:29.753 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Returning cached instance of singleton bean 'yfRegistry'
Registry{id='yfRegistry', address='127.0.0.1', port=8080}

Process finished with exit code 0

完整源码地址:https://gitee.com/yyhcsfy/LearningDemo/tree/master/spring-custom-tag

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