Metacat

/**

 *  '$RCSfile$'

 *    Purpose: A Class that implements org.xml.sax.EntityResolver interface

 *             for resolving external entities

 *  Copyright: 2000 Regents of the University of California and the

 *             National Center for Ecological Analysis and Synthesis

 *    Authors: Jivka Bojilova, Matt Jones

 *

 *   '$Author: jones $'

 *     '$Date: 2000-06-29 17:52:04 -0700 (Thu, 29 Jun 2000) $'

 * '$Revision: 245 $'

 */

package edu.ucsb.nceas.metacat;

import org.xml.sax.*;

import java.sql.*;

import java.io.File;

import java.io.FileReader;

import java.io.InputStream;

import java.io.IOException;

import java.net.URL;

import java.net.URLConnection;

import java.net.MalformedURLException;

import java.util.Stack;

import java.util.EmptyStackException;

/** 

 * A database aware Class implementing EntityResolver interface for the SAX 

 * parser to call when processing the XML stream and intercepting any 

 * external entities (including the external DTD subset and external 

 * parameter entities, if any) before including them.

 */

public class DBEntityResolver implements EntityResolver

{

   private Connection conn = null;

   private DBSAXHandler handler = null;

   /** 

    * Construct an instance of the DBEntityResolver class

    *

    * @param conn the JDBC connection to which information is written

    */

   public DBEntityResolver(Connection conn)

   {

      this.conn = conn;

   }

   /** 

    * Construct an instance of the DBEntityResolver class

    *

    * @param conn the JDBC connection to which information is written

    * @param handler the SAX handler to determine parsing context

    */

   public DBEntityResolver(Connection conn, DBSAXHandler handler)

   {

      this(conn);

      this.handler = handler;

   }

   /** 

    * The Parser call this method before opening any external entity 

    * except the top-level document entity (including the external DTD subset,

    * external entities referenced within the DTD, and external entities 

    * referenced within the document element)

    */

   public InputSource resolveEntity (String publicId, String systemId)

                throws SAXException, IOException

   {

     String dbSystemId;

     String doctype = null;

     if (publicId != null) {       // If we have a public ID, use it

       doctype = publicId;

       MetaCatUtil.debugMessage("DOCTYPE-c: " + doctype);

     } else if (systemId != null) {  // Otherwise, use system id if we can

       if (handler != null) {        // Won't have a handler under all cases

         if (handler.processingDTD()) {  // Assume the public ID is the docname

           doctype = handler.getDocname();

           MetaCatUtil.debugMessage("DOCTYPE-d: " + doctype);

         }

       }

     }    

     // look at the db XML Catalog and get dbSystemId for this doctype

     if (doctype != null) {

       dbSystemId = getDTDSystemID (conn, doctype);

       if (dbSystemId == null) {

         MetaCatUtil.debugMessage("  RESOLVED NOTHING");

         // if it is not found in the database, then

         // register publicId in db and use the provided systemId

         if (systemId != null) {

           InputStream istream = checkURLConnection(systemId);

           if (handler != null) {    // Won't have a handler under all cases

             if (handler.processingDTD()) {

               registerDTDSystemID (conn, doctype, doctype, systemId);

             }

           }

           return null;

         }

       } else {

         MetaCatUtil.debugMessage("  RESOLVED SYSTEMID: " + dbSystemId);

         // If it is in the database, return the systemid from the database

         InputStream istream = checkURLConnection(dbSystemId);

         InputSource is = new InputSource(dbSystemId);

         is.setByteStream(istream);

         MetaCatUtil.debugMessage("  INPUTSOURCE SYSTEMID: " 

                                      + is.getSystemId());

         return is;

       } 

     }

     // use the provided systemID for other cases

     InputStream istream = checkURLConnection(systemId);

     return null;

   }

   /** 

    * Look at db XML Catalog to get System ID (if any) for that doctype.

    * Return empty string if there are not 

    */

   private String getDTDSystemID (Connection conn, String doctype)  {

        String system_id = null;

        Statement stmt;

        try {

          stmt = conn.createStatement();

          stmt.execute("SELECT system_id FROM xml_catalog " + 

                       "WHERE entry_type = 'DTD' AND public_id = '" + 

                       doctype + "'");

          try {

            ResultSet rs = stmt.getResultSet();

            try {

              boolean tableHasRows = rs.next();

              if (tableHasRows) {

                try {

                  system_id = rs.getString(1);

                } catch (SQLException e) {

                  System.out.println("DBEntityResolver.getDTDSystemID() " +

                             "- Error with getString: " + e.getMessage());

                }

              }

            } catch (SQLException e) {

              System.out.println("DBEntityResolver.getDTDSystemID() " +

                             "- Error with next: " + e.getMessage());

            }

          } catch (SQLException e) {

            System.out.println("DBEntityResolver.getDTDSystemID() " +

                             "- Error with getrset: " + e.getMessage());

          }

          stmt.close();

        } catch (SQLException e) {

          System.out.println("DBEntityResolver.getDTDSystemID() " +

                             "- Error getting id: " + e.getMessage());

        }

        // return the selected System ID

        return system_id;

   }

   /** 

    * Register DTD System ID in db XML Catalog 

    */

   private void registerDTDSystemID (Connection conn, String doctype, 

                                     String publicId, String systemId)

   {

     try {

       PreparedStatement pstmt;

       pstmt = conn.prepareStatement(

             "INSERT INTO xml_catalog " +

             "(catalog_id, entry_type, source_doctype, " +

             "public_id, system_id) " +

             "VALUES (null, 'DTD', ?, ?, ?)");

       // Bind the values to the query

       pstmt.setString(1, doctype);

       pstmt.setString(2, publicId);

       pstmt.setString(3, systemId);

       // Do the insertion

       pstmt.execute();

       pstmt.close();

     } catch (SQLException e) {

       System.out.println(e.getMessage());

     }

   }

   /** 

    * Check URL Connection for systemId, and return an InputStream

    * that can be used to read from the systemId URL.  The parser ends

    * up using this via the InputSource to read the DTD.

    *

    * @param systemID a URI (in practice URL) to be checked and opened

    */

   private InputStream checkURLConnection (String systemId)

                throws MalformedURLException, IOException

   {

     try {

       return (new URL(systemId).openStream());

     } catch (MalformedURLException e) {

       System.out.println("from checkURLConnection(): " + e.getMessage());

       throw e;

     } catch (IOException e) {

       System.out.println("from checkURLConnection(): " + e.getMessage());

       throw e;

     }    

   }   

}

/**

 * '$Log$

 * 'Revision 1.13  2000/06/29 23:27:08  jones

 * 'Fixed bug in DBEntityResolver so that it now properly delegates to

 * 'the system id found inthe database.

 * 'Changed DBValidate to use DBEntityResolver, rather than the OASIS

 * 'catalog, and to return validation results in XML format.

 * '

 * 'Revision 1.12  2000/06/27 04:31:07  jones

 * 'Fixed bugs associated with the new UPDATE and DELETE functions of

 * 'DBWriter.  There were problematic interactions between some static

 * 'variables used in DBEntityResolver and the way in which the

 * 'Servlet objects are re-used across multiple client invocations.

 * '

 * 'Generally cleaned up error reporting.  Now all errors and success

 * 'results are reported as XML documents from MetaCatServlet.  Need

 * 'to make the command line tools do the same.

 * '

 * 'Revision 1.11  2000/06/26 10:35:04  jones

 * 'Merged in substantial changes to DBWriter and associated classes and to

 * 'the MetaCatServlet in order to accomodate the new UPDATE and DELETE

 * 'functions.  The command line tools and the parameters for the

 * 'servlet have changed substantially.

 * '

 * 'Revision 1.10.2.2  2000/06/25 23:38:16  jones

 * 'Added RCSfile keyword

 * '

 * 'Revision 1.10.2.1  2000/06/25 23:34:17  jones

 * 'Changed documentation formatting, added log entries at bottom of source files

 * ''

 */