source: tmcsimulator/trunk/src/atmsdriver/ExchangeReader.java @ 79

package atmsdriver;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.StringReader;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.helpers.DefaultHandler;

/**
 *
 * @author John A Torres
 */
public class ExchangeReader {
        /** Error Log **/
        private static Logger ATMSDriverLogger = Logger.getLogger("atmsdriver");
        
        /** A SAX Handler that is used to parse received Incident Status Node. **/
        private IncidentStatusHandler ish = null;
        
        /** The current networkId **/
        private int networkId = 1;
        
        /** The Paramics Simulation Info for the most recent incident read **/
        private ExchangeInfo exInfo = null;
        
        /** Value (seconds since 1/1/1970) of input file's last modification time. */
        private long lastModified = 0;
        
        /**
         * Constructor.
         */
        public ExchangeReader() 
        {               
                ish = new IncidentStatusHandler();
        }
        
        /**
         * This method parses the received XML node with the local CameraStatusHandler.
         * All updated camera information is sent to the ParamicsSimulationManager.
         * 
         * If a successful read of the file occurs, the file is written with an empty string
         * and the date of the last modification is stored.
         *
         * @param filename The file to check for message in.
         * @return A ParamicsSimulationInfo object containing the file's information
         *                 A null pointer on:
         *                   - The file does not exist
         *                   - No new modification
         *                   - An error opening file              
         *           - An empty file
         *           - An error parsing the file
         *           
         *         The caller is able to call this function to check if there are any new messages
         *         in the file.  If there are, a PSI object is returned.  If there aren't any new
         *         messages, a null pointer is returned.
         */
        public ExchangeInfo parse(String filename) 
        {       
                ExchangeInfo exInfo = null;
                
                File f = new File(filename);
                BufferedReader r = null;
                
                // File does not exist: No information
                if (!(f.exists()))
                {
                        return null;
                }
                
                // File not modified: No new information
                if (f.lastModified() <= lastModified)
                {
                        return null;
                }
                
                try 
                {
                        // Try to open the file
                        r = new BufferedReader(new FileReader(f));
                        
                        // Read the file to the end
                        StringBuilder xml = new StringBuilder("");
                        String line = r.readLine();
                        while (line != null)
                        {
                                xml.append(line + "\n");
                                line = r.readLine();
                        }
                        
                        // If the file has contents in it, read them and returned a PSI describing the contents
                        if(xml.length() > 0) 
                        {
                                // Parse the file
                                SAXParserFactory.newInstance().newSAXParser().parse(new InputSource(new StringReader(xml.toString())), ish);
                                exInfo = new ExchangeInfo(networkId, xml.toString());
                        }
                        else if (xml.length() == 0)
                        {
                                lastModified = modifyFile(f);
                                r.close();
                        }
                }
                catch (FileNotFoundException fnfe)
                {
                        ATMSDriverLogger.logp(Level.SEVERE, "ParamicsIncidentReader", "parse", 
                                        filename + " dissapeared before reading.", fnfe);
                        exInfo = null;
                }
                catch (IOException ioe)
                {
                        ATMSDriverLogger.logp(Level.SEVERE, "ParamicsIncidentReader", "parse", 
                                        "Error while reading file " + filename + ".", ioe);
                        exInfo = null;
                }
                catch (SAXException saxe)
                {
                        ATMSDriverLogger.logp(Level.SEVERE, "ParamicsIncidentReader", "parse", 
                                        "Error while parsing file " + filename + ".", saxe);
                        exInfo = null;
                }
                catch (ParserConfigurationException pce)
                {
                        ATMSDriverLogger.logp(Level.SEVERE, "ParamicsIncidentReader", "parse", 
                                        "Error while configuring parser.", pce);
                }
                
                // If a incident was read
                if (exInfo != null)
                {
                        lastModified = modifyFile(f);
                        try
                        {
                                r.close();
                        }
                        catch (IOException e)
                        {
                                ATMSDriverLogger.logp(Level.SEVERE, "ParamicsIncidentReader", "parse", 
                                                "Error while closing file" + filename + ".", e);
                        }                       
                }
                
                // Return no object if there was an error while reading, or the psi created from
                // parsing the file if the operation was successful.
                return exInfo;
        }
        
        private long modifyFile(File f)
        {
                FileWriter w = null;
                
                // Write to the file to show that it was read.
                try
                {
                        w = new FileWriter(f);
                        w.write("");
                        w.close();
                }
                catch (IOException e)
                {
                        ATMSDriverLogger.logp(Level.SEVERE, "ParamicsIncidentReader", "parse", 
                                        "Error while writing to file " + f.getName() + " to show that file was read.", e);
                }
                
                // Save the last modified time
                return f.lastModified();
        }

    /**
     * Internal SAX Handler used to parse the Incident Status Document read by
     * the remote Status Reader.  The schema for this document is: <br/>
     *
         * <CAD_DATA><br>
         *    <Basic><br>
         *       <Comm_Interval/><br/>
         *       <Network_ID/><br/>
         *       <Simulation/><br/>
         *       <Incident/><br/>
         *    </Basic>
         *
         *    <Simulation_Data>
         *       <Simulation_speed/><br/>
         *       <CAD_clock><br/>
         *          <hour/><br/>
         *          <minute/><br/>
         *          <second/><br/>
         *          <Location><br/>
         *       </CAD_clock><br/>
         *    </Simulation_Data>
         *    
         *    <CAD_Incidents>
         *       <Incident><br/>
         *          <Identifier/><br/>
         *          <Status/><br/>
         *          <Location><br/>
         *              <Route/><br/>
         *              <Direction/><br/>
         *              <Location_type/><br/>
         *              <Postmile/><br/>
         *          </Location><br/>
         *          <Incident_type/><br/>
         *          <Lanes><br/>
         *             <Lane_number/><br/>
         *             ...
         *          </Lanes><br/>
         *       </Incident><br/>
         *       ...
         *    </CAD_Incidents>   
         *    
         *    <Management>
         *       <Diversion>
     *          <Diversion_path>
     *             <Identifier/>
     *             <Percentage/>
     *          <Diversion_path>
     *          ...
     *       </Diversion>
     *       ...
         *    </Management>
         *  
         * </CAD_DATA>
     */ 
        protected class IncidentStatusHandler extends DefaultHandler 
        {
                private final String NETWORK_ID   = "Network_ID";
                
                /** A buffer for reading characters **/
                private StringBuffer parsedValue  = new StringBuffer();

                public void startDocument() 
                { 
                }       
                
                /** Appends characters to the xmlMessage and parsedValue buffers **/
                public void characters(char[] ch, int start, int length) 
                {
                        parsedValue.append(new String(ch, start, length).trim());
                }
                
            public void startElement (String uri, String localName, String qName, Attributes attributes)
                        throws SAXException
                {
            }
                
                public void endElement(String uri, String localName, String qName)  
                {
                        if(qName.equals(NETWORK_ID)) { networkId = Integer.parseInt(parsedValue.toString()); }
                        
                        parsedValue.setLength(0);
                }       
                
                public void error(SAXParseException e) 
                {
                        ATMSDriverLogger.logp(Level.SEVERE, "ParamicsIncidentReader", "error", 
                                        "Error in parsing received incident status.", e);
                }
                
                public void fatalError(SAXParseException e) 
                {
                        ATMSDriverLogger.logp(Level.SEVERE, "ParamicsIncidentReader", "fatalError", 
                                        "Fatal error in parsing received incident status.", e);
                }
                
                public void warning(SAXParseException e) 
                {
                        ATMSDriverLogger.logp(Level.WARNING, "ParamicsIncidentReader", "warning", 
                                        "Warning in parsing received incident status.", e);
                }               
        }
}