我正在尝试编写一个验证脚本,它将根据nitf dtd来验证xml,http://www.iptc.org/std/NITF/3.4/specification/dtd/nitf-3-4.dtd。基于this post我提出了以下简单的脚本来验证nitf xml文档。下面是我在运行脚本时收到的错误消息,这不是很好的描述,而且很难调试。如有任何帮助,我们将不胜感激。
#!/usr/bin/env python
def main():
from lxml import etree, objectify
from StringIO import StringIO
f = open('nitf_test.xml')
xml_doc = f.read()
f.close()
f = open('nitf-3-4.dtd')
dtd_doc = f.read()
f.close()
dtd = etree.DTD(StringIO(dtd_doc))
tree = objectify.parse(StringIO(xml_doc))
dtd.validate(tree)
if __name__ == '__main__':
main()
回溯错误消息:
Traceback (most recent call last):
File "./test_nitf_doc.py", line 23, in <module>
main()
File "./test_nitf_doc.py", line 16, in main
dtd = etree.DTD(StringIO(dtd_doc))
File "dtd.pxi", line 43, in lxml.etree.DTD.__init__ (src/lxml/lxml.etree.c:126056)
File "dtd.pxi", line 117, in lxml.etree._parseDtdFromFilelike (src/lxml/lxml.etree.c:126727)
lxml.etree.DTDParseError: error parsing DTD
如果我换线:
dtd = etree.DTD(StringIO(dtd_doc))
到:
dtd = etree.DTD(dtd_doc)
我得到的错误是:
lxml.etree.DTDParseError: failed to load external entity "NULL"
最佳答案
我看了一下nitf-3-4.dtd
,发现它引用了一个可以downloaded at this link的外部模块xhtml-ruby-1.mod
。这需要存在于当前目录中,以便dtd解析器可以加载它。
完整的工作示例(假设您手头有一个有效的NITF文档):
% wget http://www.iptc.org/std/NITF/3.4/specification/dtd/nitf-3-4.dtd
% wget http://www.iptc.org/std/NITF/3.4/specification/dtd/xhtml-ruby-1.mod
Python代码:
from lxml import etree, objectify
dtd = etree.DTD(open('nitf-3-4.dtd', 'rb'))
tree = objectify.parse(open('nitf_test.xml', 'rb'))
print dtd.validate(tree)
输出:
% python nitf_test.py
True