如何使用org.xml.sax.ext.EntityResolver2 resolveEntity方法获取非空名称参数？

Question

在Java SAX处理中，我不能设法从org.xml.sax.ext.EntityResolver2 resolveEntity方法获得实体引用名称。即使文档中声明'name' is never null when invoked by a SAX2 parser，name参数也始终为null。

有什么想法吗？

为了演示这个问题，我创建了一个Jython2.5脚本。它打印(在我的盒子上)：

Entity Resolver 2 enabled: True
Entity name: None

Jython 2.5脚本：

# Jython
from org.python.core.util import StringUtil
from jarray import array

# Java Standard Edition
from org.xml.sax import *
from org.xml.sax.ext import *
from org.xml.sax.helpers import *
from java.io import ByteArrayInputStream

xml = """\
<!DOCTYPE doc
[<!ENTITY entity SYSTEM "entity-file">
]>
<doc>&entity;</doc>
"""

def empty_source():
    _source = InputSource()
    byte_stream = ByteArrayInputStream(array([], "b"))
    _source.setByteStream(byte_stream)
    return _source

class Handler(EntityResolver2):
    def getExternalSubset(self, name, baseURI):
        return None
    def resolveEntity(self, name, publicId, baseURI, systemId):
        print "Entity name:", name 
        return empty_source()

reader = XMLReaderFactory.createXMLReader()
enabled = reader.getFeature("http://xml.org/sax/features/use-entity-resolver2")
print "Entity Resolver 2 enabled:", enabled 

handler = Handler()
reader.setEntityResolver(handler) 
bytes = StringUtil.toBytes(xml)
byte_stream = ByteArrayInputStream(bytes)
source = InputSource(byte_stream)
reader.parse(source)

Answer 1

使用较新版本的Xerces (例如2.9.1)，而不是与Java捆绑在一起的“旧”版本。