Metacat

/**

 *      Name: DBEntityResolver.java

 *   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

 *

 *   Version: '$Id: DBEntityResolver.java 151 2000-06-13 21:22:02Z bojilova $'

 */

package edu.ucsb.nceas.metacat;

import org.xml.sax.*;

import java.sql.*;

import java.net.URL;

import java.net.URLConnection;

import java.net.MalformedURLException;

import java.io.IOException;

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

{

   static String doctype = null;

   private Connection conn = null;

   private int pIdCounter = 0;

   private long currentElementNo;

   /** Construct an instance of the DBEntityResolver clas

    *

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

    */

   public DBEntityResolver(Connection conn)

   {

      this.conn = conn;

   }

   /** 

    * 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 MalformedURLException, IOException

   {

     String dbSystemId;

     currentElementNo = DBSAXHandler.elementNo;

     if (currentElementNo == 0) {

        if (publicId != null) {

            pIdCounter += 1;

            doctype = publicId;

        } else if ( systemId != null) {

            doctype = DBSAXHandler.docname;

        }    

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

        dbSystemId = getDTDSystemID (conn, doctype);

        if (dbSystemId == "") {

            // register publicId in db and use the provided systemId

            if (systemId != "") {

                checkURLConnection(systemId);

                registerDTDSystemID (conn, doctype, doctype, systemId);

                return null;

            }

        } else {

            checkURLConnection(dbSystemId);

            return new InputSource(dbSystemId);

        } 

     }

     // use the default behaviour

     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 = "";

        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());

          System.exit(1);

        }

        // 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 

    */

   private void checkURLConnection (String systemId)

                throws MalformedURLException, IOException

   {

        try {

            URLConnection urlConn = (new URL(systemId)).openConnection();

            urlConn.connect();

        } catch (MalformedURLException e) {

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

            throw e;

        } catch (IOException e) {

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

            throw e;

        }    

   }   

}