可扩展XML-Schema机制

Java

万世威

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 2018/12/26   Share

可扩展XML-Schema机制

扩展流程

可扩展Schema机制

实例

XSD文件

<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema
        xmlns="http://www.demo.com/schema/people"
        xmlns:xsd="http://www.w3.org/2001/XMLSchema"
        xmlns:beans="http://www.springframework.org/schema/beans"
        targetNamespace="http://www.demo.com/schema/people"
        elementFormDefault="qualified">
    <xsd:import namespace="http://www.springframework.org/schema/beans" />
    <xsd:element name="people">
        <xsd:complexType>
            <xsd:complexContent>
                <xsd:extension base="beans:identifiedType">
                    <xsd:attribute name="name" type="xsd:string"/>
                    <xsd:attribute name="age" type="xsd:int"/>
                </xsd:extension>
            </xsd:complexContent>
        </xsd:complexType>
    </xsd:element>
</xsd:schema>

配置文件

// META-INF/spring.handlers
http\://www.demo.com/schema/people=com.mvc.schema.MySchemaNameSpaceHandler

// META-INF/spring.schemas
http\://www.demo.com/schema/people/people.xsd=META-INF/people.xsd

实体类

public class People {
    private String id;
    private String name;
    private Integer age;
    public People() {}
    @Override
    public String toString() {
        return "People{" +
                "id='" + id + '\'' +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
}

NameSpaceHandler

import org.springframework.beans.factory.xml.NamespaceHandlerSupport;
public class MySchemaNameSpaceHandler extends NamespaceHandlerSupport{
    @Override
    public void init() {
        registerBeanDefinitionParser("people", new  		                              				PeopleBeanDefinitionParser(People.class));
    }
}

BeanDefinitionParser

import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.beans.factory.xml.BeanDefinitionParser;
import org.springframework.beans.factory.xml.ParserContext;
import org.w3c.dom.Element;
public class PeopleBeanDefinitionParser implements BeanDefinitionParser {

    private final Class<?> beanClass;

    public PeopleBeanDefinitionParser(Class<?> beanClass) {
        this.beanClass = beanClass;
    }

    @Override
    public BeanDefinition parse(Element element, ParserContext parserContext) {
        String name = element.getAttribute("name");
        String age = element.getAttribute("age");
        String id = element.getAttribute("id");
        // 存放Bean信息的类
        RootBeanDefinition beanDefinition = new RootBeanDefinition();
        beanDefinition.setBeanClass(beanClass);
        beanDefinition.setLazyInit(false);
        if (null != id) {
            beanDefinition.getPropertyValues().add("id", id);
        }
        if (null != name) {
            beanDefinition.getPropertyValues().add("name", name);
        }
        if (null != age) {
            beanDefinition.getPropertyValues().add("age", age);
        }
        // 注册到Spring容器中
        parserContext.getRegistry().registerBeanDefinition("people", beanDefinition);
        return beanDefinition;
    }
}

目录结构

src
	-- com.dist.schema
		-- People.java
		-- MySchemaNameSpaceHandler.java
		-- PeopleBeanDefinitionParser.java
resources
	-- META-INF
		-- people.xsd
		-- spring.handlers
		-- spring.schemas
	-- spring.xml

XML信息

<?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:people="http://www.demo.com/schema/people"
       xsi:schemaLocation="
		http://www.demo.com/schema/people
		http://www.demo.com/schema/people/people.xsd">

    <people:people id="people" name="wansw" age="123"/>

</beans>

测试类

@Test
public void testXML() {
    ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("spring-mvc.xml");
    People people = (People)context.getBean("people");
    System.out.println(people.toString());
}
/**
People{id='people', name='wansw', age=123}
/

执行过程

在Spring解析XML，遇到自定义Element时，调用 parseCustomElement 方法：

// org/springframework/beans/factory/xml/BeanDefinitionParserDelegate.java
public BeanDefinition parseCustomElement(Element ele, BeanDefinition containingBd) {
   String namespaceUri = getNamespaceURI(ele);
   NamespaceHandler handler = this.readerContext.getNamespaceHandlerResolver().resolve(namespaceUri);
   if (handler == null) {
      return null;
   }
   return handler.parse(ele, new ParserContext(this.readerContext, this, containingBd));
}

@Override
public NamespaceHandler resolve(String namespaceUri) {
   Map<String, Object> handlerMappings = getHandlerMappings();
   Object handlerOrClassName = handlerMappings.get(namespaceUri);
   if (handlerOrClassName == null) {
      return null;
   }
   else if (handlerOrClassName instanceof NamespaceHandler) {
      return (NamespaceHandler) handlerOrClassName;
   }
   else {
      String className = (String) handlerOrClassName;
      try {
         Class<?> handlerClass = ClassUtils.forName(className, this.classLoader);
         if (!NamespaceHandler.class.isAssignableFrom(handlerClass)) {
            throw new FatalBeanException();
         }
         NamespaceHandler namespaceHandler = (NamespaceHandler) BeanUtils.instantiateClass(handlerClass);
         // 执行 init 方法，调用NamespaceHandler(MySchemaNameSpaceHandler)的init方法
         namespaceHandler.init();
         handlerMappings.put(namespaceUri, namespaceHandler);
         return namespaceHandler;
      }
   }
}

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