Spring IOC Part 4: Analysis of Custom Labels

In -depth analysis of the code delegate.parseCustomElement(ele);

For dubbo , it uses the functional features of spring custom tag parsing. The process of Spring custom tag parsing is as follows:

1. Create a component that needs to be extended
2. Define an XSD description file content
3. Create a class that implements the BeanDefinitionParser interface to parse definitions in XSD files and definitions in components
4. Create a Handler component that extends NamespaceHandlerSupport to register the component with the Spring container
5. Writing Spring.handlers and Spring.schemas files

Now start using custom tag parsing by following the steps above

1. Create a class to receive the properties in the configuration file

 

public class People {
        private String id;  
        private String name;  
        private Integer age; 
// 省略get/set方法

1. Create an xsd file describing the xml syntax constraints

2. <?xml version="1.0" encoding="UTF-8"?>  
   <xsd:schema   
       xmlns="http://blog.csdn.net/cutesource/schema/people"  
       xmlns:xsd="http://www.w3.org/2001/XMLSchema"   
       xmlns:beans="http://www.springframework.org/schema/beans"  
       targetNamespace="http://blog.csdn.net/cutesource/schema/people"  
       elementFormDefault="qualified"   
       attributeFormDefault="unqualified">  
       <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>  
   The age and name attributes are defined in xsd, which correspond to the attributes in the people entity one by one

   1. Create a file that implements the BeanDefinitionParser interface to parse definitions in XSD and XML files

   2. package com.spring.test.parser;
      
      import org.springframework.beans.factory.support.BeanDefinitionBuilder;
      import org.springframework.beans.factory.xml.AbstractSingleBeanDefinitionParser;
      import org.springframework.util.StringUtils;
      import org.w3c.dom.Element;
      
      import com.spring.test.pojo.People;
      
      public class PeopleBeanDefinitionParser extends AbstractSingleBeanDefinitionParser {
          // Element对应的类
       @Override
          protected Class getBeanClass(Element element) {  
              return People.class;  
      }  
      
      // Parse and extract the corresponding element from element 
           @Override
           protected  void doParse(Element element, BeanDefinitionBuilder bean) {  
              String name = element.getAttribute("name");  
              String age = element.getAttribute("age");  
              String id = element.getAttribute("id" );  
               if (StringUtils.hasText(id)) {  
             // Put the extracted data into BeanDefinitionBuilder, after parsing is completed, put it into unified registration to beanFactory 
                  bean.addPropertyValue("id" , id);  
              }  
              if (StringUtils.hasText(name)) {  
                  bean.addPropertyValue("name", name);  
              }  
              if (StringUtils.hasText(age)) {  
                  bean.addPropertyValue("age", Integer.valueOf(age));  
              }  
          }  
      }