The R Project SVN R

/*==============================================================================

  Project: Simple JAVA Search Engine for Keyword Search

  JAVA Source file for the class SearchEngine

  COPYRIGHT (C), 1998, Thomas Baier

  ALL RIGHTS RESERVED.

  $Source: /scratch/CVS-ARCHIVE/R/doc/html/search/SearchEngine.java,v $

  $Revision: 1.1 $

  $Date: 1998/05/15 10:38:10 $

  $Author: leisch $

==============================================================================*/

/* -------------------------------- Imports --------------------------------- */

import java.applet.*;

import java.awt.*;

import java.net.*;

import java.io.*;

import java.util.*;

/*==============================================================================

                          Interface of class SearchEngine

==============================================================================*/

/*------------------------------------------------------------------------------

  CLASS:    SearchEngine

  SUPER:    Applet

  CONF. TO: 

  PURPOSE:  

  NOTES:    

  HISTORY:  98-04-26: created 

------------------------------------------------------------------------------*/

public class SearchEngine extends Applet

{

  /*============================================================================

                                Public methods

  ============================================================================*/

  /*----------------------------------------------------------------------------

    INTERFACE: 

    PURPOSE:   default constructor

    NOTES:     

    PARAMS:    

    THROWS:    

    RETURNS:   void

    HISTORY:   98-04-26: created

               98-05-03: now reads the index file

  ----------------------------------------------------------------------------*/

  public SearchEngine ()

  {

    iIndexTable = null;

    iSearchTerm = null;

    Tracer.write ("SearchEngine initializing\n");

    return;

  }

  /*----------------------------------------------------------------------------

    INTERFACE: 

    PURPOSE:   return general information about the applet

    NOTES:     

    PARAMS:    

    THROWS:    

    RETURNS:   String: the information

    HISTORY:   98-04-26: created

  ----------------------------------------------------------------------------*/

  public String getAppletInfo ()

  {

    return "Name: SearchEngine\r\n" +

      "Author: Thomas Baier\r\n" +

      "(C) 1998 Thomas Baier, ALL RIGHTS RESERVED";

  }

  /*----------------------------------------------------------------------------

    INTERFACE: 

    PURPOSE:   perform initialization

    NOTES:     creates the controls

    PARAMS:    

    THROWS:    

    RETURNS:   void

    HISTORY:   98-04-26: created

               98-05-03: now a do-nothing

  ----------------------------------------------------------------------------*/

  public void init ()

  {

    resize(640, 240);

    // get the name of the index file

    String indexName = getParameter (cIndexKeyword);

    String searchTerm = getParameter (cSearchKeyword);

    Tracer.write ("Index file is \"" + indexName + "\"\n");

    Tracer.write ("Search term is \"" + searchTerm + "\"\n");

    // use a default index file if none specified

    if (indexName == null) {

      indexName = cIndexFile;

    }

    iSearchTerm = searchTerm;

    /*

     * examine the URL to get the search term...

     *

     * if the URL ends with ?SEARCHTERM=xxxxx we know, xxxxx is the search term

     */

    {

      URL url = getDocumentBase ();

      String urlString = url.toString ();

      int index = urlString.indexOf ("?" + cSearchKeyword + "=");

      Tracer.write ("URL is \"" + urlString + "\"\n");

      // if found, take the rest as the search string

      if (index >= 0) {

	iSearchTerm =

	  urlString.substring (index + 2 + cSearchKeyword.length ());

	Tracer.write ("found search term \"" + iSearchTerm + "\" in URL\n");

      }

    }

    readIndexFile (indexName);

    return;

  }

  /*----------------------------------------------------------------------------

    INTERFACE: 

    PURPOSE:   perform "destructor" code

    NOTES:     not required here

    PARAMS:    

    THROWS:    

    RETURNS:   void

    HISTORY:   98-04-26: created

  ----------------------------------------------------------------------------*/

  public void destroy ()

  {

    return;

  }

  /*----------------------------------------------------------------------------

    INTERFACE: 

    PURPOSE:   perform painting of the applet

    NOTES:     not required for our applet, controls do everything

    PARAMS:    Graphics g: the graphics context to draw on

    THROWS:    

    RETURNS:   void

    HISTORY:   98-04-26: created

  ----------------------------------------------------------------------------*/

  public void paint (Graphics g)

  {

    return;

  }

  /*----------------------------------------------------------------------------

    INTERFACE: 

    PURPOSE:   perform startup code everytime visiting the applet

    NOTES:     

    PARAMS:    

    THROWS:    

    RETURNS:   void

    HISTORY:   98-04-26: created

               98-05-10: start the tracer

  ----------------------------------------------------------------------------*/

  public void start ()

  {

    Tracer.start ();

    return;

  }

  /*----------------------------------------------------------------------------

    INTERFACE: 

    PURPOSE:   perform cleanup evertime the applet "loses" the focus

    NOTES:     

    PARAMS:    

    THROWS:    

    RETURNS:   void

    HISTORY:   98-04-26: created

               98-05-10: stop the tracer

  ----------------------------------------------------------------------------*/

  public void stop ()

  {

    Tracer.stop ();

    return;

  }

  /*----------------------------------------------------------------------------

    INTERFACE: 

    PURPOSE:   perform the search and return the search results as a string

    NOTES:     

    PARAMS:    

    THROWS:    

    RETURNS:   void

    HISTORY:   98-05-03: created

               98-05-08: new format for output

	       98-05-09: added trace

	       98-05-10: now a front-end for search()

  ----------------------------------------------------------------------------*/

  public String search (String key)

  {

    iSearchTerm = key;

    return internalSearch ();

  }

  /*----------------------------------------------------------------------------

    INTERFACE: 

    PURPOSE:   perform the search (back-end)

    NOTES:     

    PARAMS:    

    THROWS:    

    RETURNS:   void

    HISTORY:   98-05-10: created

  ----------------------------------------------------------------------------*/

  public String internalSearch ()

  {

    Tracer.write ("Search for \"" + iSearchTerm + "\" started");

    Vector foundItems = null;

    if (iSearchTerm != null) {

      foundItems = iIndexTable.search (iSearchTerm);

    } else {

      foundItems = null;

    }

    String result = null;

    // if nothing found, return a special string

    if (foundItems == null) {

      result = "No matches for <b>\"" + 

	iSearchTerm +

	"\"</b> have been found!<hr>";

    } else {

      Enumeration cursor = foundItems.elements ();

      result =

	"The search string was <b>\"" +

	iSearchTerm +

	"<b>\"" +

	"<hr>" +

	"<dl>";

      while (cursor.hasMoreElements ()) {

	IndexEntry entry = (IndexEntry) cursor.nextElement ();

	/*

	 * the format for every entry is

	 *

	 * title

	 *   description

	 */

	result +=

	  "<dt><a href=\"" +

	  entry.getURL () +

	  "\">" +

	  entry.getTitle () +

	  "</a></dt>\n";

	result += "<dd>" + entry.getDescription () + "</dd>\n";

      }

      result += "</dl>";

    }

    return result;

  }

  /*============================================================================

                              Protected methods

  ============================================================================*/

  /*============================================================================

                               Private methods

  ============================================================================*/

  /*----------------------------------------------------------------------------

    INTERFACE: 

    PURPOSE:   read the index file

    NOTES:     

    PARAMS:    

    THROWS:    

    RETURNS:   void

    HISTORY:   98-04-26: created

               98-05-08: now use an IndexStream

	       98-05-10: also use prefix and suffix, build URL from first key

  ----------------------------------------------------------------------------*/

  private void readIndexFile (String idxFile)

  {

    // create the index table

    iIndexTable = new IndexTable ();

    URL baseURL = getCodeBase ();

    // get the index file and parse its contents

    try {

      URL idxFileURL = new URL (baseURL,idxFile);

      // get an IndexStream object for ease of parsing

      IndexStream idxStream = new IndexStream (idxFileURL);

      // now start parsing...

      /*

       * An entry consists of a title, keywords, an URL and a description.

       * everything else is ignored. Every entry starts with the keyword

       * "Entry" (case is ignored)

       *

       * must-have entries are "Entry" and "Keywords"

       */

      String entry = null;

      String keywords = null;

      String url = null;

      String description = "";

      String prefix = "";

      String suffix = "";

      Value value = idxStream.popEntry ();

      while (value != null) {

	// parse the value now

	if (value.getKey ().equalsIgnoreCase ("entry")) {

	  // if a new entry is about to start, add the current one

	  addEntry (entry,keywords,description,url,prefix,suffix);

	  entry = value.getValue ();

	  keywords = null;

	  url = null;

	  description = "";

	} else if (value.getKey ().equalsIgnoreCase ("keywords")) {

	  keywords = value.getValue ();

	} else if (value.getKey ().equalsIgnoreCase ("url")) {

	  // use prefix and suffix

	  url = prefix + value.getValue () + suffix;

	} else if (value.getKey ().equalsIgnoreCase ("description")) {

	  description = value.getValue ();

	} else if (value.getKey ().equalsIgnoreCase ("prefix")) {

	  prefix = value.getValue ();

	  Tracer.write ("using new URL prefix \"" + prefix + "\"\n");

	} else if (value.getKey ().equalsIgnoreCase ("suffix")) {

	  suffix = value.getValue ();

	  Tracer.write ("using new URL suffix \"" + suffix + "\"\n");

	}

	value = idxStream.popEntry ();

      }

      // the final entry just read

      addEntry (entry,keywords,description,url,prefix,suffix);

    } catch (MalformedURLException exc) {

      // an error occured while reading...

    }

    return;

  }

  /*----------------------------------------------------------------------------

    INTERFACE: 

    PURPOSE:   

    NOTES:     

    PARAMS:    

    THROWS:    

    RETURNS:   void

    HISTORY:   98-05-10: created

  ----------------------------------------------------------------------------*/

  private void addEntry (String entry,String keywords,

			 String description,String url,

			 String prefix,String suffix)

  {

    // the entry must be set

    if (entry == null) {

      return;

    }

    // the keywords must be set, else ignore it

    if (keywords != null) {

      if (url == null) {

	// if the URL is empty, construct one following the rule:

	// URL = prefix + first keyword + suffix

	int endOfFirstKeyword = keywords.indexOf (" ");

	// because we have trimmed the string, the first character must

	// not be a blank

	if (endOfFirstKeyword >= 0) {

	  url = keywords.substring (0,endOfFirstKeyword);

	  Tracer.write ("constructing URL, keywords=\"" +

			keywords + "\"" +

			"using \"" + 

			url +

			"\" (results in \"" +

			prefix + url + suffix + "\")\n");

	} else {

	  // just a single keyword

	  url = keywords;

	  Tracer.write ("constructing URL, using keyword \"" + 

			url +

			"\" (results in \"" +

			prefix + url + suffix + "\")\n");

	}

	// add prefix and suffix

	url = prefix + url + suffix;

      }

      IndexEntry idxEntry =

	new IndexEntry (entry,keywords,description,url);

      iIndexTable.addElement (idxEntry);

    }

    return;

  }

  /*============================================================================

                             Instance Variables

  ============================================================================*/

  private IndexTable iIndexTable;

  private String     iSearchTerm;

  /*============================================================================

                                Static Data

  ============================================================================*/

  private static final String cIndexFile = "index.txt";

  private static final String cIndexKeyword = "INDEXFILE";

  private static final String cSearchKeyword = "SEARCHTERM";

}

/*==============================================================================

  HISTORY:

  $Log: SearchEngine.java,v $

  Revision 1.1  1998/05/15 10:38:10  leisch

  New: Search Engine

  Revision 1.4  1998/05/10 22:56:53  baier

  internal search function, parameter expansion

  Revision 1.3  1998/05/10 02:44:32  baier

  traces, output in HTML via JavaScript, new index generation

  Revision 1.2  1998/04/26 22:36:34  baier

  documentation changes

  Revision 1.1  1998/04/26 21:32:54  baier

  Initial revision

==============================================================================*/

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