XmlReader引发多个DTD错误 [英] XmlReader throws multiple DTDs error

问题描述

假设我们要加载xml（cXML）并针对我们在本地存储的DTD进行验证。这是此代码：

Let's say we want to load an xml (cXML) and validate it against a DTD that we have stored locally. Here's the code for this:

XmlPreloadedResolver resolver = new XmlPreloadedResolver(XmlKnownDtds.None);
resolver.Add(new Uri(DocTypeSystemId), File.ReadAllText(@"C:\cXml.dtd"));
XmlReaderSettings settings = new XmlReaderSettings
{
    ValidationType = ValidationType.DTD,
    DtdProcessing = DtdProcessing.Parse             
};
settings.ValidationEventHandler += Settings_ValidationEventHandler;

XmlParserContext context = new XmlParserContext(null, null, "cXML", null, 
                               DocTypeSystemId, null, null, null, XmlSpace.None);

XmlReader reader = XmlReader.Create(stream, settings, context);
XDocument doc = XDocument.Load(reader);

不幸的是，如果cXML输入已经带有DTD定义，则XmlReader将抛出XmlException声明： 消息不能有多个DTD。第2行，位置1。

Unfortunately in case the cXML input already comes with a DTD definition, the XmlReader will throw an XmlException stating: Message Cannot have multiple DTDs. Line 2, position 1.

如果我们从输入中删除DOCTYPE，则会显示警告未找到DTD。 并且xml未被验证。

If we remove the DOCTYPE from the input a warning is shown No DTD found. and the xml isn't validated.

似乎XmlReader很难使用XmlParserContext。

It seems that XmlReader has hard time using an XmlParserContext.

推荐答案

相反，阅读器是过时的 XmlTextReader 的实例：

If instead the reader is an instance of the obsolete XmlTextReader:

XmlTextReader textReader = new XmlTextReader(stream, XmlNodeType.Document, context);
XmlValidatingReader reader = new XmlValidatingReader(textReader);
reader.ValidationType = ValidationType.DTD;
reader.ValidationEventHandler += Settings_ValidationEventHandler;

然后，多个DTD都没有例外，并且xml进行了验证。

Then there is no exception for multiple DTDs and the xml is validated.

很明显，XmlTextReader和XmlReader的功能有所不同。当xml缺少暂停验证的DOCTYPE时，它们似乎都输出警告。误解 XmlValidatingReaderImpl.ProcessCoreReaderEvent（）和 DtdValidator.Validate（）（其中 schemaInfo.SchemaType == SchemaType.DTD 为假，也许是因为它不存在DTD。）

Obviously there is a difference between how XmlTextReader and XmlReader function. They both seem to output a warning when the xml is missing a DOCTYPE which halts validation. The following calls are involved in the misunderstanding XmlValidatingReaderImpl.ProcessCoreReaderEvent() and DtdValidator.Validate() (where schemaInfo.SchemaType == SchemaType.DTD is false maybe because it's no DTD exists).

最好只是尝试在输入xml中更改/添加DOCTYPE元素，而不是与 XmlParserContext 和不同的阅读器实现作斗争。

With all this in mind it seems better to just try to change/add the DOCTYPE element in the input xml than battle with XmlParserContext and the different reader implementations.

这篇关于XmlReader引发多个DTD错误的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！