Parser: resolveEntity

Question

我很难弄清楚如何将自己的ResolveEntityHandler绑定到SAX解析器。在那里，这个答案。但不幸的是，我无法在那里复制结果。

当我运行以下代码(实际上是从上述答案中复制的)时，只更新到Python 3，

import io
import xml.sax
from xml.sax.handler import ContentHandler

# Inheriting from EntityResolver and DTDHandler is not necessary
class TestHandler(ContentHandler):

    # This method is only called for external entities. Must return a value.
    def resolveEntity(self, publicID, systemID):
        print ("TestHandler.resolveEntity(): %s %s" % (publicID, systemID))
        return systemID

    def skippedEntity(self, name):
        print ("TestHandler.skippedEntity(): %s" % (name))

    def unparsedEntityDecl(self, name, publicID, systemID, ndata):
        print ("TestHandler.unparsedEntityDecl(): %s %s" % (publicID, systemID))

    def startElement(self, name, attrs):
        summary = attrs.get('summary', '')
        print ('TestHandler.startElement():', summary)

def main(xml_string):
    try:
        parser = xml.sax.make_parser()
        curHandler = TestHandler()
        parser.setContentHandler(curHandler)
        parser.setEntityResolver(curHandler)
        parser.setDTDHandler(curHandler)

        stream = io.StringIO(xml_string)
        parser.parse(stream)
        stream.close()
    except xml.sax.SAXParseException as e:
        print ("ERROR %s" % e)

XML = """<!DOCTYPE test SYSTEM "test.dtd">
<test summary='step: &num;'>Entity: &not;</test>
"""

main(XML)

和外部test.dtd

<!ENTITY num "FOO">
<!ENTITY pic SYSTEM 'bar.gif' NDATA gif>

我得到的是

TestHandler.startElement(): step: 
TestHandler.skippedEntity(): not

Process finished with exit code 0

所以我的问题是：

1. 为什么从来没有叫过resolveEntity？
2. 如何将ResolveEntityHandler绑定到解析器？

Answer 1

你所看到的与Python 3.7.1中的更改有关

在3.7.1版本中更改: SAX解析器在默认情况下不再处理一般外部实体以增加安全性。在此之前，解析器创建网络连接，从DTD和实体的文件系统中获取远程文件或加载的本地文件。可以使用解析器对象上的方法setFeature()和参数feature_external_ges再次启用该特性。

若要获得与早期版本相同的行为，请添加以下行：

from xml.sax.handler import feature_external_ges

和(在main函数中)

parser.setFeature(feature_external_ges, True)