java - JAXBContext 和 Marshaller 更改 XML namespace 的顺序

Question

我有这样一行代码:

StringWriter writer = new StringWriter(); 
JAXBContext jc = JAXBContext.newInstance(namespace);
Marshaller marshaller = jc.createMarshaller();        
marshaller.marshal(input, writer);

当 namespace = "nfpa:nfpares" 时。我有一个这样的生成内容:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ServiceRequest xmlns:ns2="nfpares" xmlns="nfpa">
...
</ServiceRequest>

但不知何故，在库的另一部分(我无法控制)，开发人员也使用 JAXBContext 和相同的命名空间，但生成的内容是:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ServiceRequest xmlns="nfpa" xmlns:ns2="nfpares">
...
</ServiceRequest>

请注意 namespace 仍然相同，但它们的顺序已调换。我需要对原始内容进行加密验证。除了命名空间的顺序外，这两者之间的一切都是一样的。有谁知道发生了什么事？因为我使用了不同版本的 JAXBContext？

谢谢

Answer 1

在对 xml 进行加密签名检查时，您需要使用规范形式的 xml。对于与 XML 解析器相同的相同 XML 结构，有许多不同的序列化可能性。例如<a/>对比<a></a> ,  对比 或属性和命名空间的顺序。 XML canonicalization 有一个标准它描述了以下转换:

The canonical form of an XML document is physical representation of the document produced by the method >described in this specification. The changes are summarized in the following list:

• The document is encoded in UTF-8
• Line breaks normalized to #xA on input, before parsing
• Attribute values are normalized, as if by a validating processor
• Character and parsed entity references are replaced
• CDATA sections are replaced with their character content
• The XML declaration and document type declaration (DTD) are removed
• Empty elements are converted to start-end tag pairs
• Whitespace outside of the document element and within start and end tags is normalized
• All whitespace in character content is retained (excluding characters removed during line feed normalization)
• Attribute value delimiters are set to quotation marks (double quotes)
• Special characters in attribute values and character content are replaced by character references
• Superfluous namespace declarations are removed from each element
• Default attributes are added to each element
• Lexicographic order is imposed on the namespace declarations and attributes of each element

此方法的实现可以在 apache xml security project 中找到在类里面Canonicalizer