Source Code for Module ndg.xacml.utils.xpath_selector

 1  """XPath selection for XACML AttributeSelector 
 2  """ 
 3  __author__ = "R B Wilkinson" 
 4  __date__ = "23/12/11" 
 5  __copyright__ = "(C) 2011 Science and Technology Facilities Council" 
 6  __license__ = "BSD - see LICENSE file in top-level directory" 
 7  __contact__ = "Philip.Kershaw@stfc.ac.uk" 
 8  __revision__ = "$Id$" 
 9   
10  from abc import ABCMeta, abstractmethod 
11   
12  from ndg.xacml import Config, importElementTree 
13  ElementTree = importElementTree() 
14   
15 -class XPathSelectorInterface(object): 
16      """Interface for XPath selectors. 
17      """ 
18      __metaclass__ = ABCMeta 
19   
20      @abstractmethod 
21 -    def __init__(self, contextElem): 
22          """ 
23          @type contextElem: type of an XML element appropriate to implementation 
24          @param contextElem: context element on which searches are based 
25          """ 
26          pass 
27   
28      @abstractmethod 
29 -    def selectText(self, path): 
30          """Performs an XPath search and returns text content of matched 
31          elements. 
32          @type path: str 
33          @param path: XPath path expression 
34          @rtype: list of basestr 
35          @return: text from selected elements 
36          """ 
37          pass 
38   
39 -class EtreeXPathSelector(XPathSelectorInterface): 
40      """XPathSelectorInterface using ElementTree XPath selection. 
41      """ 
42 -    def __init__(self, contextElem): 
43          """ 
44          @type contextElem: ElementTree.Element 
45          @param contextElem: context element on which searches are based 
46          """ 
47          if not ElementTree.iselement(contextElem): 
48              raise TypeError("Expecting %r input type for parsing; got %r" % 
49                              (ElementTree.Element, contextElem)) 
50          self.contextElem = contextElem 
51   
52      if Config.use_lxml: 
53 -        def selectText(self, path): 
54              """Performs an XPath search and returns text content of matched 
55              elements. 
56              @type path: str 
57              @param path: XPath path expression 
58              @rtype: list of basestring 
59              @return: text from selected elements 
60              """ 
61              # ElementTree XPath doesn't support absolute paths. Make it relative 
62              # to context element. 
63              if path.startswith('/'): 
64                  relPath = '.' + path 
65              else: 
66                  relPath = path 
67              find = ElementTree.ETXPath(relPath) 
68              elems = find(self.contextElem) 
69              returnList = [] 
70              for m in elems: 
71                  # Allow for XPath expression selecting element text or attribute 
72                  # values. 
73                  if hasattr(m, 'text'): 
74                      returnList.append(m.text) 
75                  else: 
76                      returnList.append(m.__str__()) 
77              return returnList 
78      else: 
79 -        def selectText(self, path): 
80              """Performs an XPath search and returns text content of matched 
81              elements. 
82              @type path: str 
83              @param path: XPath path expression 
84              @rtype: list of basestring 
85              @return: text from selected elements 
86              """ 
87              # ElementTree XPath doesn't support absolute paths. Make it relative 
88              # to context element. 
89              if path.startswith('/'): 
90                  relPath = '.' + path 
91              else: 
92                  relPath = path 
93              elems = self.contextElem.findall(relPath) 
94              return [e.text for e in elems] 
95