EntityResolver解析

2024-02-03 12:42:28

spring解析XML，SAX首先读取该XML文件上的声明，根据声明去寻找相应的DTD定义，以便对文档做验证。默认的寻找规则是通过网络（声明的DTD的URL地址）来下载相应的DTD声明，并进行验证。由于出于网络的原因，spring提供了一个自定义寻找DTD/XSD声明的方式。

spring解析XML的代码：

protected Document doLoadDocument(InputSource inputSource, Resource resource) throws Exception {
   return this.documentLoader.loadDocument(inputSource, getEntityResolver(), this.errorHandler,
         getValidationModeForResource(resource), isNamespaceAware());
}

public interface EntityResolver {
    InputSource resolveEntity(String publicId, String systemId) throws SAXException, IOException;
}

spring使用DelegatingEntityResolver实现类来解析XML的自定义声明

public InputSource resolveEntity(@Nullable String publicId, @Nullable String systemId)
      throws SAXException, IOException {

   if (systemId != null) {
      if (systemId.endsWith(DTD_SUFFIX)) {
         return this.dtdResolver.resolveEntity(publicId, systemId);
      }
      else if (systemId.endsWith(XSD_SUFFIX)) {
         return this.schemaResolver.resolveEntity(publicId, systemId);
      }
   }

   // Fall back to the parser's default behavior.
   return null;
}