1  This file was updated on Saturday, 2012-10-13 at 3:13 PM
  2  
  3  
  4  ======================================================================
  5  sample.xml
  6  ======================================================================
  7  
  8  
  9  <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 10  <!--
 11    File:   sample.xml
 12    Author: Jesse M. Heines, UMass Lowell CS, heines@cs.uml.edu
 13  
 14    Downloaded on October 13, 2012, 2:55 PM
 15    Source:  http://www.yolinux.com/TUTORIALS/XML-Xerces-C.html
 16  -->
 17  <root>
 18     <ApplicationSettings
 19             option_a = "10"
 20             option_b = "24"
 21             >
 22     </ApplicationSettings>
 23     <OtherStuff
 24             option_x = "500"
 25             >
 26     </OtherStuff>
 27  </root>
 28  
 29  
 30  ======================================================================
 31  parser.hpp
 32  ======================================================================
 33  
 34  
 35  /*
 36   * File:   parser.hpp
 37   * Author: Jesse M. Heines, UMass Lowell CS, heines@cs.uml.edu
 38   *
 39   * Downloaded on October 13, 2012, 2:55 PM
 40   * Source:  http://www.yolinux.com/TUTORIALS/XML-Xerces-C.html
 41   */
 42  
 43  #ifndef XML_PARSER_HPP
 44  #define XML_PARSER_HPP
 45  /**
 46   *  @file
 47   *  Class "GetConfig" provides the functions to read the XML data.
 48   *  @version 1.0
 49   */
 50  #include <xercesc/dom/DOM.hpp>
 51  #include <xercesc/dom/DOMDocument.hpp>
 52  #include <xercesc/dom/DOMDocumentType.hpp>
 53  #include <xercesc/dom/DOMElement.hpp>
 54  #include <xercesc/dom/DOMImplementation.hpp>
 55  #include <xercesc/dom/DOMImplementationLS.hpp>
 56  #include <xercesc/dom/DOMNodeIterator.hpp>
 57  #include <xercesc/dom/DOMNodeList.hpp>
 58  #include <xercesc/dom/DOMText.hpp>
 59  
 60  #include <xercesc/parsers/XercesDOMParser.hpp>
 61  #include <xercesc/util/XMLUni.hpp>
 62  
 63  #include <string>
 64  #include <stdexcept>
 65  
 66  // Error codes
 67  
 68  enum {
 69     ERROR_ARGS = 1,
 70     ERROR_XERCES_INIT,
 71     ERROR_PARSE,
 72     ERROR_EMPTY_DOCUMENT
 73  };
 74  
 75  class GetConfig
 76  {
 77  public:
 78     GetConfig();
 79    ~GetConfig();
 80     void readConfigFile(std::string&) throw(std::runtime_error);
 81  
 82     char *getOptionA() { return m_OptionA; };
 83     char *getOptionB() { return m_OptionB; };
 84  
 85  private:
 86     xercesc::XercesDOMParser *m_ConfigFileParser;
 87     char* m_OptionA;
 88     char* m_OptionB;
 89  
 90     // Internal class use only. Hold Xerces data in UTF-16 SMLCh type.
 91  
 92     XMLCh* TAG_root;
 93  
 94     XMLCh* TAG_ApplicationSettings;
 95     XMLCh* ATTR_OptionA;
 96     XMLCh* ATTR_OptionB;
 97  };
 98  #endif
 99  
100  
101  ======================================================================
102  parser.cpp
103  ======================================================================
104  
105  
106  /*
107   * File:   parser.cpp
108   * Author: Jesse M. Heines, UMass Lowell CS, heines@cs.uml.edu
109   *
110   * Downloaded on October 13, 2012, 3:03 PM
111   * Source:  http://www.yolinux.com/TUTORIALS/XML-Xerces-C.html
112   */
113  
114  #include <string>
115  #include <iostream>
116  #include <sstream>
117  #include <stdexcept>
118  #include <list>
119  
120  #include <sys/types.h>
121  #include <sys/stat.h>
122  #include <unistd.h>
123  #include <errno.h>
124  
125  #include "parser.hpp"
126  
127  using namespace xercesc;
128  using namespace std;
129  
130  /**
131   *  Constructor initializes xerces-C libraries.
132   *  The XML tags and attributes which we seek are defined.
133   *  The xerces-C DOM parser infrastructure is initialized.
134   */
135  
136  GetConfig::GetConfig()
137  {
138     try
139     {
140        XMLPlatformUtils::Initialize();  // Initialize Xerces infrastructure
141     }
142     catch( XMLException& e )
143     {
144        char* message = XMLString::transcode( e.getMessage() );
145        cerr << "XML toolkit initialization error: " << message << endl;
146        XMLString::release( &message );
147        // throw exception here to return ERROR_XERCES_INIT
148     }
149  
150     // Tags and attributes used in XML file.
151     // Can't call transcode till after Xerces Initialize()
152     TAG_root        = XMLString::transcode("root");
153     TAG_ApplicationSettings = XMLString::transcode("ApplicationSettings");
154     ATTR_OptionA = XMLString::transcode("option_a");
155     ATTR_OptionB = XMLString::transcode("option_b");
156  
157     m_ConfigFileParser = new XercesDOMParser;
158  }
159  
160  /**
161   *  Class destructor frees memory used to hold the XML tag and
162   *  attribute definitions. It als terminates use of the xerces-C
163   *  framework.
164   */
165  
166  GetConfig::~GetConfig()
167  {
168     // Free memory
169  
170     delete m_ConfigFileParser;
171     if(m_OptionA)   XMLString::release( &m_OptionA );
172     if(m_OptionB)   XMLString::release( &m_OptionB );
173  
174     try
175     {
176        XMLString::release( &TAG_root );
177  
178        XMLString::release( &TAG_ApplicationSettings );
179        XMLString::release( &ATTR_OptionA );
180        XMLString::release( &ATTR_OptionB );
181     }
182     catch( ... )
183     {
184        cerr << "Unknown exception encountered in TagNamesdtor" << endl;
185     }
186  
187     // Terminate Xerces
188  
189     try
190     {
191        XMLPlatformUtils::Terminate();  // Terminate after release of memory
192     }
193     catch( xercesc::XMLException& e )
194     {
195        char* message = xercesc::XMLString::transcode( e.getMessage() );
196  
197        cerr << "XML ttolkit teardown error: " << message << endl;
198        XMLString::release( &message );
199     }
200  }
201  
202  /**
203   *  This function:
204   *  - Tests the access and availability of the XML configuration file.
205   *  - Configures the xerces-c DOM parser.
206   *  - Reads and extracts the pertinent information from the XML config file.
207   *
208   *  @param in configFile The text string name of the HLA configuration file.
209   */
210  
211  void GetConfig::readConfigFile(string& configFile)
212          throw( std::runtime_error )
213  {
214     // Test to see if the file is ok.
215  
216     struct stat fileStatus;
217  
218     int iretStat = stat(configFile.c_str(), &fileStatus);
219     if( iretStat == ENOENT )
220        throw ( std::runtime_error("Path file_name does not exist, or path is an empty string.") );
221     else if( iretStat == ENOTDIR )
222        throw ( std::runtime_error("A component of the path is not a directory."));
223     else if( iretStat == ELOOP )
224        throw ( std::runtime_error("Too many symbolic links encountered while traversing the path."));
225     else if( iretStat == EACCES )
226        throw ( std::runtime_error("Permission denied."));
227     else if( iretStat == ENAMETOOLONG )
228        throw ( std::runtime_error("File can not be read\n"));
229  
230     // Configure DOM parser.
231  
232     m_ConfigFileParser->setValidationScheme( XercesDOMParser::Val_Never );
233     m_ConfigFileParser->setDoNamespaces( false );
234     m_ConfigFileParser->setDoSchema( false );
235     m_ConfigFileParser->setLoadExternalDTD( false );
236  
237     try
238     {
239        m_ConfigFileParser->parse( configFile.c_str() );
240  
241        // no need to free this pointer - owned by the parent parser object
242        DOMDocument* xmlDoc = m_ConfigFileParser->getDocument();
243  
244        // Get the top-level element: NAme is "root". No attributes for "root"
245  
246        DOMElement* elementRoot = xmlDoc->getDocumentElement();
247        if( !elementRoot ) throw(std::runtime_error( "empty XML document" ));
248  
249        // Parse XML file for tags of interest: "ApplicationSettings"
250        // Look one level nested within "root". (child of root)
251  
252        DOMNodeList*      children = elementRoot->getChildNodes();
253        const  XMLSize_t nodeCount = children->getLength();
254  
255        // For all nodes, children of "root" in the XML tree.
256  
257        for( XMLSize_t xx = 0; xx < nodeCount; ++xx )
258        {
259           DOMNode* currentNode = children->item(xx);
260           if( currentNode->getNodeType() &&  // true is not NULL
261               currentNode->getNodeType() == DOMNode::ELEMENT_NODE ) // is element
262           {
263              // Found node which is an Element. Re-cast node as element
264              DOMElement* currentElement
265                          = dynamic_cast< xercesc::DOMElement* >( currentNode );
266              if( XMLString::equals(currentElement->getTagName(), TAG_ApplicationSettings))
267              {
268                 // Already tested node as type element and of name "ApplicationSettings".
269                 // Read attributes of element "ApplicationSettings".
270                 const XMLCh* xmlch_OptionA
271                       = currentElement->getAttribute(ATTR_OptionA);
272                 m_OptionA = XMLString::transcode(xmlch_OptionA);
273  
274                 const XMLCh* xmlch_OptionB
275                       = currentElement->getAttribute(ATTR_OptionB);
276                 m_OptionB = XMLString::transcode(xmlch_OptionB);
277  
278                 break;  // Data found. No need to look at other elements in tree.
279              }
280           }
281        }
282     }
283     catch( xercesc::XMLException& e )
284     {
285        char* message = xercesc::XMLString::transcode( e.getMessage() );
286        ostringstream errBuf;
287        errBuf << "Error parsing file: " << message << flush;
288        XMLString::release( &message );
289     }
290  }
291  
292  // the following line was added by JMH to get main to run
293  #define MAIN_TEST
294  
295  #ifdef MAIN_TEST
296  /* This main is provided for unit test of the class. */
297  
298  int main()
299  {
300     string configFile="sample.xml"; // stat file. Get ambigious segfault otherwise.
301  
302     GetConfig appConfig;
303  
304     appConfig.readConfigFile(configFile);
305  
306     cout << "Application option A="  << appConfig.getOptionA()  << endl;
307     cout << "Application option B="  << appConfig.getOptionB()  << endl;
308  
309     return 0;
310  }
311  #endif
312  
314  
315  ======================================================================