Source Code for Module ndg.saml.utils.factory

  1  """ 
  2  Class Factory for NDG SAML package 
  3   
  4  NERC DataGrid project 
  5  """ 
  6  __author__ = "Philip Kershaw" 
  7  __date__ = "15/02/10" 
  8  __copyright__ = "(C) 2010 Science and Technology Facilities Council" 
  9  __license__ = "http://www.apache.org/licenses/LICENSE-2.0" 
 10  __contact__ = "Philip.Kershaw@stfc.ac.uk" 
 11  __revision__ = '$Id:$' 
 12  import traceback 
 13  import logging, os, sys 
 14  log = logging.getLogger(__name__) 
 15   
 16   
 17 -def importModuleObject(moduleName, objectName=None, objectType=None): 
 18      '''Import from a string module name and object name.  Object can be 
 19      any entity contained in a module 
 20       
 21      @param moduleName: Name of module containing the class 
 22      @type moduleName: str  
 23      @param objectName: Name of the class to import.  If none is given, the  
 24      class name will be assumed to be the last component of modulePath 
 25      @type objectName: str 
 26      @rtype: class object 
 27      @return: imported class''' 
 28      if objectName is None: 
 29          if ':' in moduleName: 
 30              # Support Paste style import syntax with rhs of colon denoting  
 31              # module content to import 
 32              _moduleName, objectName = moduleName.rsplit(':', 1) 
 33              if '.' in objectName: 
 34                  objectName = objectName.split('.') 
 35          else:  
 36              try: 
 37                  _moduleName, objectName = moduleName.rsplit('.', 1) 
 38              except ValueError: 
 39                  raise ValueError('Invalid module name %r set for import: %s' % 
 40                                   (moduleName, traceback.format_exc())) 
 41      else: 
 42          _moduleName = moduleName 
 43           
 44      if isinstance(objectName, basestring): 
 45          objectName = [objectName] 
 46       
 47      log.debug("Importing %r ..." % objectName)  
 48         
 49      module = __import__(_moduleName, globals(), locals(), []) 
 50      components = _moduleName.split('.') 
 51      try: 
 52          for component in components[1:]: 
 53              module = getattr(module, component) 
 54      except AttributeError: 
 55          raise AttributeError("Error importing %r: %s" % 
 56                               (objectName, traceback.format_exc())) 
 57   
 58      importedObject = module 
 59      for i in objectName: 
 60          importedObject = getattr(importedObject, i) 
 61   
 62      # Check class inherits from a base class 
 63      if objectType and not issubclass(importedObject, objectType): 
 64          raise TypeError("Specified class %r must be derived from %r; got %r" % 
 65                          (objectName, objectType, importedObject)) 
 66       
 67      log.info('Imported %r from module, %r', objectName, _moduleName) 
 68      return importedObject 
 69   
 70   
 71 -def callModuleObject(moduleName, objectName=None, moduleFilePath=None,  
 72                       objectType=None, objectArgs=None, objectProperties=None): 
 73      ''' 
 74      Create and return an instance of the specified class or invoke callable 
 75      @param moduleName: Name of module containing the class 
 76      @type moduleName: str  
 77      @param objectName: Name of the class to instantiate.  May be None in  
 78      which case, the class name is parsed from the moduleName last element 
 79      @type objectName: str 
 80      @param moduleFilePath: Path to the module - if unset, assume module on  
 81      system path already 
 82      @type moduleFilePath: str 
 83      @param objectProperties: dict of properties to use when instantiating the  
 84      class 
 85      @type objectProperties: dict 
 86      @param objectType: expected type for the object to instantiate - to  
 87      enforce use of specific interfaces  
 88      @type objectType: object 
 89      @return: object - instance of the class specified  
 90      ''' 
 91   
 92      # ensure that properties is a dict - NB, it may be passed in as a null 
 93      # value which can override the default val 
 94      if not objectProperties: 
 95          objectProperties = {} 
 96   
 97      if not objectArgs: 
 98          objectArgs = () 
 99           
100      # variable to store original state of the system path 
101      sysPathBak = None 
102      try: 
103          try: 
104              # Module file path may be None if the new module to be loaded 
105              # can be found in the existing system path             
106              if moduleFilePath: 
107                  if not os.path.exists(moduleFilePath): 
108                      raise IOError("Module file path '%s' doesn't exist" %  
109                                    moduleFilePath) 
110                             
111                  # Temporarily extend system path ready for import 
112                  sysPathBak = sys.path 
113                             
114                  sys.path.append(moduleFilePath) 
115   
116               
117              # Import module name specified in properties file 
118              importedObject = importModuleObject(moduleName,  
119                                                  objectName=objectName, 
120                                                  objectType=objectType) 
121          finally: 
122              # revert back to original sys path, if necessary 
123              # NB, python requires the use of a try/finally OR a try/except  
124              # block - not both combined 
125              if sysPathBak: 
126                  sys.path = sysPathBak 
127                               
128      except Exception, e: 
129          log.error('%r module import raised %r type exception: %r' %  
130                    (moduleName, e.__class__, traceback.format_exc())) 
131          raise  
132   
133      # Instantiate class 
134      log.debug('Instantiating object "%s"' % importedObject.__name__) 
135      try: 
136          if objectArgs: 
137              object = importedObject(*objectArgs, **objectProperties) 
138          else: 
139              object = importedObject(**objectProperties) 
140               
141          return object 
142   
143      except Exception, e: 
144          log.error("Instantiating module object, %r: %r" %  
145                                                      (importedObject.__name__,  
146                                                       traceback.format_exc())) 
147          raise 
148