Metacat

/**

 *  '$RCSfile$'

 *    Purpose: A Class that represents an XML document

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

 *             National Center for Ecological Analysis and Synthesis

 *    Authors: Matt Jones

 *    Release: @release@

 *

 *   '$Author: bojilova $'

 *     '$Date: 2000-09-20 13:15:58 -0700 (Wed, 20 Sep 2000) $'

 * '$Revision: 459 $'

 */

package edu.ucsb.nceas.metacat;

import java.sql.*;

import java.io.File;

import java.io.FileReader;

import java.io.IOException;

import java.io.PrintWriter;

import java.io.Reader;

import java.io.StringWriter;

import java.io.Writer;

import java.util.Iterator;

import java.util.Stack;

import java.util.TreeSet;

import org.xml.sax.AttributeList;

import org.xml.sax.ContentHandler;

import org.xml.sax.DTDHandler;

import org.xml.sax.EntityResolver;

import org.xml.sax.ErrorHandler;

import org.xml.sax.InputSource;

import org.xml.sax.XMLReader;

import org.xml.sax.SAXException;

import org.xml.sax.SAXParseException;

import org.xml.sax.helpers.XMLReaderFactory;

/**

 * A class that represents an XML document. It can be created with a simple

 * document identifier from a database connection.  It also will write an

 * XML text document to a database connection using SAX.

 */

public class DocumentImpl {

  static final int ALL = 1;

  static final int WRITE = 2;

  static final int READ = 4;

  private Connection conn = null;

  private String docid = null;

  private String docname = null;

  private String doctype = null;

  private String system_id = null;

  private long rootnodeid;

  private ElementNode rootNode = null;

  private String doctitle = null;

  private TreeSet nodeRecordList = null;

  /**

   * Constructor, creates document from database connection, used 

   * for reading the document

   *

   * @param conn the database connection from which to read the document

   * @param docid the identifier of the document to be created

   */

  public DocumentImpl(Connection conn, String docid) throws McdbException 

  {

    try {

      this.conn = conn;

      this.docid = docid;

      // Look up the document information

      getDocumentInfo(docid);

      // Download all of the document nodes using a single SQL query

      // The sort order of the records is determined by the NodeComparator

      // class, and needs to represent a depth-first traversal for the

      // toXml() method to work properly

      nodeRecordList = getNodeRecordList(rootnodeid);

    } catch (McdbException ex) {

      throw ex;

    } catch (Throwable t) {

      throw new McdbException("Error reading document " + docid + ".");

    }

  }

  /** 

   * Construct a new document instance, writing the contents to the database.

   * This method is called from DBSAXHandler because we need to know the

   * root element name for documents without a DOCTYPE before creating it.

   *

   * @param conn the JDBC Connection to which all information is written

   * @param rootnodeid - sequence id of the root node in the document

   * @param docname - the name of DTD, i.e. the name immediately following 

   *        the DOCTYPE keyword ( should be the root element name ) or

   *        the root element name if no DOCTYPE declaration provided

   *        (Oracle's and IBM parsers are not aware if it is not the 

   *        root element name)

   * @param doctype - Public ID of the DTD, i.e. the name immediately 

   *                  following the PUBLIC keyword in DOCTYPE declaration or

   *                  the docname if no Public ID provided or

   *                  null if no DOCTYPE declaration provided

   *

   */

  public DocumentImpl(Connection conn, long rootnodeid, String docname, 

                      String doctype, String docid, String action, String user)

                      throws SQLException, Exception

  {

    this.conn = conn;

    this.rootnodeid = rootnodeid;

    this.docname = docname;

    this.doctype = doctype;

    this.docid = docid;

    writeDocumentToDB(action, user);

  }

  /**

   * get the document name

   */

  public String getDocname() {

    return docname;

  }

  /**

   * get the document type (which is the PublicID)

   */

  public String getDoctype() {

    return doctype;

  }

  /**

   * get the system identifier

   */

  public String getSystemID() {

    return system_id;

  }

  /**

   * get the root node identifier

   */

  public long getRootNodeID() {

    return rootnodeid;

  }

  /** 

   * Get the document identifier (docid)

   */

  public String getDocID() {

    return docid;

  }

  /**

   * Print a string representation of the XML document

   */

  public String toString()

  {

    StringWriter docwriter = new StringWriter();

    this.toXml(docwriter);

    String document = docwriter.toString();

    return document;

  }

  /**

   * Get a text representation of the XML document as a string

   * This older algorithm uses a recursive tree of Objects to represent the

   * nodes of the tree.  Each object is passed the data for the document 

   * and searches all of the document data to find its children nodes and

   * recursively build.  Thus, because each node reads the whole document,

   * this algorithm is extremely slow for larger documents, and the time

   * to completion is O(N^N) wrt the number of nodes.  See toXml() for a

   * better algorithm.

   */

  public String readUsingSlowAlgorithm()

  {

    StringBuffer doc = new StringBuffer();

    // Create the elements from the downloaded data in the TreeSet

    rootNode = new ElementNode(nodeRecordList, rootnodeid);

    // Append the resulting document to the StringBuffer and return it

    doc.append("<?xml version=\"1.0\"?>\n");

    if (docname != null) {

      if ((doctype != null) && (system_id != null)) {

        doc.append("<!DOCTYPE " + docname + " PUBLIC \"" + doctype + 

                   "\" \"" + system_id + "\">\n");

      } else {

        doc.append("<!DOCTYPE " + docname + ">\n");

      }

    }

    doc.append(rootNode.toString());

    return (doc.toString());

  }

  /**

   * Print a text representation of the XML document to a Writer

   *

   * @param pw the Writer to which we print the document

   */

  public void toXml(Writer pw)

  {

    PrintWriter out = null;

    if (pw instanceof PrintWriter) {

      out = (PrintWriter)pw;

    } else {

      out = new PrintWriter(pw);

    }

    MetaCatUtil util = new MetaCatUtil();

    Stack openElements = new Stack();

    boolean atRootElement = true;

    boolean previousNodeWasElement = false;

    // Step through all of the node records we were given

    Iterator it = nodeRecordList.iterator();

    while (it.hasNext()) {

      NodeRecord currentNode = (NodeRecord)it.next();

      //util.debugMessage("[Got Node ID: " + currentNode.nodeid +

                          //" (" + currentNode.parentnodeid +

                          //", " + currentNode.nodeindex + 

                          //", " + currentNode.nodetype + 

                          //", " + currentNode.nodename + 

                          //", " + currentNode.nodedata + ")]");

      // Print the end tag for the previous node if needed

      //

      // This is determined by inspecting the parent nodeid for the

      // currentNode.  If it is the same as the nodeid of the last element

      // that was pushed onto the stack, then we are still in that previous

      // parent element, and we do nothing.  However, if it differs, then we

      // have returned to a level above the previous parent, so we go into

      // a loop and pop off nodes and print out their end tags until we get

      // the node on the stack to match the currentNode parentnodeid

      //

      // So, this of course means that we rely on the list of elements

      // having been sorted in a depth first traversal of the nodes, which

      // is handled by the NodeComparator class used by the TreeSet

      if (!atRootElement) {

        NodeRecord currentElement = (NodeRecord)openElements.peek();

        if ( currentNode.parentnodeid != currentElement.nodeid ) {

          while ( currentNode.parentnodeid != currentElement.nodeid ) {

            currentElement = (NodeRecord)openElements.pop();

            util.debugMessage("\n POPPED: " + currentElement.nodename);

            if (previousNodeWasElement) {

              out.print(">");

              previousNodeWasElement = false;

            }  

            out.print("</" + currentElement.nodename + ">" );

            currentElement = (NodeRecord)openElements.peek();

          }

        }

      }

      // Handle the DOCUMENT node

      if (currentNode.nodetype.equals("DOCUMENT")) {

        out.println("<?xml version=\"1.0\"?>");

        if (docname != null) {

          if ((doctype != null) && (system_id != null)) {

            out.println("<!DOCTYPE " + docname + " PUBLIC \"" + doctype + 

                       "\" \"" + system_id + "\">");

          } else {

            out.println("<!DOCTYPE " + docname + ">");

          }

        }

      // Handle the ELEMENT nodes

      } else if (currentNode.nodetype.equals("ELEMENT")) {

        if (atRootElement) {

          atRootElement = false;

        } else {

          if (previousNodeWasElement) {

            out.print(">");

          }

        }

        openElements.push(currentNode);

        util.debugMessage("\n PUSHED: " + currentNode.nodename);

        previousNodeWasElement = true;

        out.print("<" + currentNode.nodename);

      // Handle the ATTRIBUTE nodes

      } else if (currentNode.nodetype.equals("ATTRIBUTE")) {

        out.print(" " + currentNode.nodename + "=\""

                 + currentNode.nodedata + "\"");

      } else if (currentNode.nodetype.equals("TEXT")) {

        if (previousNodeWasElement) {

          out.print(">");

        }

        out.print(currentNode.nodedata);

        previousNodeWasElement = false;

      // Handle the COMMENT nodes

      } else if (currentNode.nodetype.equals("COMMENT")) {

        if (previousNodeWasElement) {

          out.print(">");

        }

        out.print("<!--" + currentNode.nodedata + "-->");

        previousNodeWasElement = false;

      // Handle the PI nodes

      } else if (currentNode.nodetype.equals("PI")) {

        if (previousNodeWasElement) {

          out.print(">");

        }

        out.print("<?" + currentNode.nodename + " " +

                        currentNode.nodedata + "?>");

        previousNodeWasElement = false;

      // Handle any other node type (do nothing)

      } else {

        // Any other types of nodes are not handled.

        // Probably should throw an exception here to indicate this

      }

      out.flush();

    }

    // Print the final end tag for the root element

    NodeRecord currentElement = (NodeRecord)openElements.pop();

    util.debugMessage("\n POPPED: " + currentElement.nodename);

    out.print("</" + currentElement.nodename + ">" );

    out.flush();

  }

  /**

   * Look up the document type information from the database

   *

   * @param docid the id of the document to look up

   */

  private void getDocumentInfo(String docid) throws McdbException 

  {

    PreparedStatement pstmt;

    try {

      pstmt =

        conn.prepareStatement("SELECT docname,doctype,rootnodeid " +

                                "FROM xml_documents " +

                               "WHERE docid LIKE ?");

      // Bind the values to the query

      pstmt.setString(1, docid);

      pstmt.execute();

      ResultSet rs = pstmt.getResultSet();

      boolean tableHasRows = rs.next();

      if (tableHasRows) {

        this.docname    = rs.getString(1);

        this.doctype    = rs.getString(2);

        this.rootnodeid = rs.getLong(3);

      } 

      pstmt.close();

      if (this.doctype != null) {

        pstmt =

          conn.prepareStatement("SELECT system_id " +

                                  "FROM xml_catalog " +

                                 "WHERE public_id LIKE ?");

        // Bind the values to the query

        pstmt.setString(1, doctype);

        pstmt.execute();

        rs = pstmt.getResultSet();

        tableHasRows = rs.next();

        if (tableHasRows) {

          this.system_id  = rs.getString(1);

        } 

        pstmt.close();

      }

    } catch (SQLException e) {

      throw new McdbException("Error accessing database connection.", e);

    }

    if (this.docname == null) {

      throw new McdbDocNotFoundException("Document not found: " + docid);

    }

  }

  /**

   * Look up the node data from the database

   *

   * @param rootnodeid the id of the root node of the node tree to look up

   */

  private TreeSet getNodeRecordList(long rootnodeid) throws McdbException 

  {

    PreparedStatement pstmt;

    TreeSet nodeRecordList = new TreeSet(new NodeComparator());

    long nodeid = 0;

    long parentnodeid = 0;

    long nodeindex = 0;

    String nodetype = null;

    String nodename = null;

    String nodedata = null;

    try {

      pstmt =

      conn.prepareStatement("SELECT nodeid,parentnodeid,nodeindex, " +

           "nodetype,nodename,"+               

           "replace(" +

           "replace(" +

           "replace(nodedata,'&','&') " +

           ",'<','&lt;') " +

           ",'>','>') " +

           "FROM xml_nodes WHERE rootnodeid = ?");

      // Bind the values to the query

      pstmt.setLong(1, rootnodeid);

      pstmt.execute();

      ResultSet rs = pstmt.getResultSet();

      boolean tableHasRows = rs.next();

      while (tableHasRows) {

        nodeid = rs.getLong(1);

        parentnodeid = rs.getLong(2);

        nodeindex = rs.getLong(3);

        nodetype = rs.getString(4);

        nodename = rs.getString(5);

        nodedata = rs.getString(6);

        // add the data to the node record list hashtable

        NodeRecord currentRecord = new NodeRecord(nodeid, parentnodeid, 

                                   nodeindex, nodetype, nodename, nodedata);

        nodeRecordList.add(currentRecord);

        // Advance to the next node

        tableHasRows = rs.next();

      } 

      pstmt.close();

    } catch (SQLException e) {

      throw new McdbException("Error accessing database connection.", e);

    }

    if (nodeRecordList != null) {

      return nodeRecordList;

    } else {

      throw new McdbException("Error getting node data: " + docid);

    }

  }

 /** creates SQL code and inserts new document into DB connection */

  private void writeDocumentToDB(String action, String user) 

               throws SQLException, Exception {

    try {

      PreparedStatement pstmt = null;

      if (action.equals("INSERT")) {

        //AccessionNumber ac = new AccessionNumber();

        //this.docid = ac.generate(docid, "INSERT");

        pstmt = conn.prepareStatement(

            "INSERT INTO xml_documents " +

            "(docid, rootnodeid, docname, doctype, " +

            "user_owner, user_updated, date_created, date_updated) " +

            "VALUES (?, ?, ?, ?, ?, ?, sysdate, sysdate)");

        // Bind the values to the query

        pstmt.setString(1, this.docid);

        pstmt.setLong(2, rootnodeid);

        pstmt.setString(3, docname);

        pstmt.setString(4, doctype);

        pstmt.setString(5, user);

        pstmt.setString(6, user);

      } else if (action.equals("UPDATE")) {

        // Save the old document entry in a backup table

        DocumentImpl.archiveDocRevision( conn, docid, user );

        // Delete index for the old version of docid

        // The new index is inserting on the next calls to DBSAXNode

        pstmt = conn.prepareStatement(

                "DELETE FROM xml_index WHERE docid='" + this.docid + "'");

        pstmt.execute();

        pstmt.close();

        // Update the new document to reflect the new node tree

        pstmt = conn.prepareStatement(

            "UPDATE xml_documents " +

            "SET rootnodeid = ?, docname = ?, doctype = ?, " +

            "user_updated = ?, date_updated = sysdate WHERE docid LIKE ?");

        // Bind the values to the query

        pstmt.setLong(1, rootnodeid);

        pstmt.setString(2, docname);

        pstmt.setString(3, doctype);

        pstmt.setString(4, user);

        pstmt.setString(5, this.docid);

      } else {

        System.err.println("Action not supported: " + action);

      }

      // Do the insertion

      pstmt.execute();

      pstmt.close();

    } catch (SQLException sqle) {

      throw sqle;

//    } catch (AccessionNumberException ane) {

//      MetaCatUtil.debugMessage("Invalid accession number.");

//      MetaCatUtil.debugMessage(ane.getMessage());

//      throw ane;

    } catch (Exception e) {

      throw e;

    }

  }

  /**

   * Get the document title

   */

  public String getTitle() {

    return doctitle;

  }

  /**

   * Set the document title

   *

   * @param title the new title for the document

   */

  public void setTitle( String title ) {

    this.doctitle = title;

    try {

      PreparedStatement pstmt;

      pstmt = conn.prepareStatement(

            "UPDATE xml_documents " +

            " SET doctitle = ? " +

            "WHERE docid = ?");

      // Bind the values to the query

      pstmt.setString(1, doctitle);

      pstmt.setString(2, docid);

      // Do the insertion

      pstmt.execute();

      pstmt.close();

    } catch (SQLException e) {

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

    }

  }

  /**

   * Look up the title of the first child element named "title"

   * and record it as the document title

   */

/*   NOT NEEDED ANY MORE

  public void setTitleFromChildElement() {

    String title = null;

    long assigned_id=0;

    PreparedStatement pstmt;

    try {

      pstmt = conn.prepareStatement(

              "SELECT nodedata FROM xml_nodes " +

              "WHERE nodetype = 'TEXT' " +

              "AND rootnodeid = ? " +

              "AND parentnodeid IN " +

              "  (SELECT nodeid FROM xml_nodes " +

              "  WHERE nodename = 'title' " +

              "  AND nodetype =  'ELEMENT' " +

              "  AND rootnodeid = ? ) " +

              "ORDER BY nodeid");

*/

      // The above query might be slow, and probably will be because

      // it gets ALL of the title elements while searching for one

      // title in a small subtree but it avoids the problem of using

      // Oracle's Hierarchical Query syntax which is not portable --

      // the commented out SQL that follows shows an equivalent query

      // using Oracle-specific hierarchical query

      /*

      pstmt = conn.prepareStatement(

              "SELECT nodedata FROM xml_nodes " +

              "WHERE nodetype = 'TEXT' " +

              "AND parentnodeid IN " +

              "(SELECT nodeid FROM xml_nodes " +

              "WHERE nodename = 'title' " +

              "START WITH nodeid = ? " +

              "CONNECT BY PRIOR nodeid = parentnodeid)");

      */

/*

      // Bind the values to the query

      pstmt.setLong(1, rootnodeid);

      pstmt.setLong(2, rootnodeid);

      pstmt.execute();

      ResultSet rs = pstmt.getResultSet();

      boolean tableHasRows = rs.next();

      if (tableHasRows) {

        title = rs.getString(1);

      }

      pstmt.close();

    } catch (SQLException e) {

      System.out.println("Error getting title: " + e.getMessage());

    }

    // assign the new title

    this.setTitle(title);

  }

*/

  /**

   * Write an XML file to the database, given a filename

   *

   * @param conn the JDBC connection to the database

   * @param filename the filename to be loaded into the database

   * @param action the action to be performed (INSERT OR UPDATE)

   * @param docid the docid to use for the INSERT OR UPDATE

   */

  public static String write( Connection conn, String filename, String action, 

                              String docid, String user, String group )

                throws Exception {

    return write(conn, new FileReader(new File(filename).toString()), 

                  action, docid, user, group);

  }

  /**

   * Write an XML file to the database, given a Reader

   *

   * @param conn the JDBC connection to the database

   * @param xml the xml stream to be loaded into the database

   * @param action the action to be performed (INSERT OR UPDATE)

   * @param docid the docid to use for the INSERT OR UPDATE

   */

  public static String write( Connection conn, Reader xml, String action, 

                              String docid, String user, String group )

                throws Exception {

    // Determine if the docid is OK for INSERT or UPDATE

    AccessionNumber ac = new AccessionNumber(conn);

    String newdocid = ac.generate(docid, action);

    if ( action.equals("UPDATE") ) {

      // check for 'write' permission for 'user' to update this document

      if ( !hasWritePermission(conn, docid, user, group) ) {

        throw new Exception("User " + user + 

              " does not have permission to update XML Document #" + docid);

      }          

    }

    try {

        XMLReader parser = initializeParser(conn, action, newdocid, user);

        conn.setAutoCommit(false);

        parser.parse(new InputSource(xml));

        conn.commit();

        conn.setAutoCommit(true);

        //return newdocid;

      } catch (SAXParseException e) {

        conn.rollback();

        conn.setAutoCommit(true);

        throw e;

      } catch (SAXException e) {

        conn.rollback();

        conn.setAutoCommit(true);

        throw e;

/*

        // If its a problem with the accession number its ok, just the 

        // accession number was regenerated

        AccessionNumberGeneratedException ang = null;

        try {

          Exception embedded = e.getException();

          if ((embedded != null) && 

              (embedded instanceof AccessionNumberGeneratedException)) {

            ang = (AccessionNumberGeneratedException)e.getException();

          }

        } catch (ClassCastException cce) {

          // Do nothing and just fall through to the ang != null test

        }

        if (ang != null) {

          conn.commit();

          conn.setAutoCommit(true);

          return (ang.getMessage());

        } else {

          conn.rollback();

          throw e;

        }

*/        

      } catch (Exception e) {

        conn.rollback();

        conn.setAutoCommit(true);

        throw e;

      }

      if ( (docid != null) && !(newdocid.equals(docid)) ) {

        return new String("New document ID generated:" + newdocid);

      } else {

        return newdocid;

      }

  }

  /**

   * Delete an XML file from the database (actually, just make it a revision

   * in the xml_revisions table)

   *

   * @param docid the ID of the document to be deleted from the database

   */

  public static void delete( Connection conn, String docid,

                                 String user, String group )

                throws Exception {

    // Determine if the docid is OK for DELETE

    AccessionNumber ac = new AccessionNumber(conn);

    String newdocid = ac.generate(docid, "DELETE");

    // check for 'write' permission for 'user' to delete this document

    if ( !hasWritePermission(conn, docid, user, group) ) {

      throw new Exception("User " + user + 

              " does not have permission to delete XML Document #" + docid);

    }

    conn.setAutoCommit(false);

    // Copy the record to the xml_revisions table

    DocumentImpl.archiveDocRevision( conn, docid, user );

    // Now delete it from the xml_documents table

    Statement stmt = conn.createStatement();

    stmt.execute("DELETE FROM xml_index WHERE docid = '" + docid + "'");

    stmt.execute("DELETE FROM xml_documents WHERE docid = '" + docid + "'");

    stmt.close();

    conn.commit();

    conn.setAutoCommit(true);

  }

  /** Check for "write" permissions from DB connection */

  private static boolean hasWritePermission(Connection conn, String docid, 

                                     String user, String group) 

                                     throws SQLException {

    // b' of the command line invocation

    if ( (user == null) && (group == null) ) {

      return true;

    }

    PreparedStatement pstmt;

    // checking if user is owner of docid

    try {

      pstmt = conn.prepareStatement(

                   "SELECT 'x' FROM xml_documents " +

                   "WHERE docid LIKE ? AND user_owner LIKE ?");

      // Bind the values to the query

      pstmt.setString(1, docid);

      pstmt.setString(2, user);

      pstmt.execute();

      ResultSet rs = pstmt.getResultSet();

      boolean hasRow = rs.next();

      pstmt.close();

      if (hasRow) {

        return true;

      }

    } catch (SQLException e) {

      throw new 

        SQLException("Error checking document's owner: " + e.getMessage());

    }

    // checking access type from xml_access table

    int accesstype = 0;

    try {

      pstmt = conn.prepareStatement(

                   "SELECT access_type FROM xml_access " +

                   "WHERE docid LIKE ? " + 

                   "AND principal_name LIKE ? " +

                   "AND principal_type = 'user' " +

                   "AND sysdate BETWEEN nvl(begin_time,sysdate) " +

                                   "AND nvl(end_time,sysdate) " +

                   "UNION " +

                   "SELECT access_type FROM xml_access " +

                   "WHERE docid LIKE ? " + 

                   "AND principal_name LIKE ? " +

                   "AND principal_type = 'group' " +

                   "AND sysdate BETWEEN nvl(begin_time,sysdate) " +

                                   "AND nvl(end_time,sysdate)");

      // Bind the values to the query

      pstmt.setString(1, docid);

      pstmt.setString(2, user);

      pstmt.setString(3, docid);

      pstmt.setString(2, group);

      pstmt.execute();

      ResultSet rs = pstmt.getResultSet();

      boolean hasRows = rs.next();

      while ( hasRows ) {

        accesstype = rs.getInt(1);

        if ( (accesstype & WRITE) == WRITE ) {

          pstmt.close();

          return true;

        }

        hasRows = rs.next();

      }

      pstmt.close();

      return false;

    } catch (SQLException e) {

      throw new 

      SQLException("Error getting document's permissions: " + e.getMessage());

    }

  }

  /**

   * Set up the parser handlers for writing the document to the database

   */

  private static XMLReader initializeParser(Connection conn,

                           String action, String docid, String user) 

                           throws Exception {

    XMLReader parser = null;

    //

    // Set up the SAX document handlers for parsing

    //

    try {

      ContentHandler chandler   = new DBSAXHandler(conn, action, docid, user);

      EntityResolver dbresolver = new DBEntityResolver(conn, 

                                      (DBSAXHandler)chandler);

      DTDHandler dtdhandler     = new DBDTDHandler(conn);

      // Get an instance of the parser

      MetaCatUtil util = new MetaCatUtil();

      String parserName = util.getOption("saxparser");

      parser = XMLReaderFactory.createXMLReader(parserName);

      // Turn off validation

      parser.setFeature("http://xml.org/sax/features/validation", false);

      // Set Handlers in the parser

      parser.setProperty("http://xml.org/sax/properties/declaration-handler",

                         chandler);

      parser.setProperty("http://xml.org/sax/properties/lexical-handler",

                         chandler);

      parser.setContentHandler((ContentHandler)chandler);

      parser.setEntityResolver((EntityResolver)dbresolver);

      parser.setDTDHandler((DTDHandler)dtdhandler);

      parser.setErrorHandler((ErrorHandler)chandler);

    } catch (Exception e) {

      throw e;

    }

    return parser;

  }

  /** Save a document entry in the xml_revisions table */

  private static void archiveDocRevision(Connection conn, String docid,

                                         String user) throws SQLException {

    // create a record in xml_revisions table 

    // for that document as selected from xml_documents

    PreparedStatement pstmt = conn.prepareStatement(

      "INSERT INTO xml_revisions " +

        "(revisionid, docid, rootnodeid, docname, doctype, doctitle, " +

        "user_owner, user_updated, date_created, date_updated) " +

      "SELECT null, ?, rootnodeid, docname, doctype, doctitle," + 

        "user_owner, ?, sysdate, sysdate "+

      "FROM xml_documents " +

      "WHERE docid = ?");

    // Bind the values to the query and execute it

    pstmt.setString(1, docid);

    pstmt.setString(2, user);

    pstmt.setString(3, docid);

    pstmt.execute();

    pstmt.close();

  }

  /**

   * the main routine used to test the DBWriter utility.

   * <p>

   * Usage: java DocumentImpl <-f filename -a action -d docid>

   *

   * @param filename the filename to be loaded into the database

   * @param action the action to perform (READ, INSERT, UPDATE, DELETE)

   * @param docid the id of the document to process

   */

  static public void main(String[] args) {

    try {

      String filename = null;

      String action   = null;

      String docid    = null;

      boolean showRuntime = false;

      boolean useOldReadAlgorithm = false;

      // Parse the command line arguments

      for ( int i=0 ; i < args.length; ++i ) {

        if ( args[i].equals( "-f" ) ) {

          filename =  args[++i];

        } else if ( args[i].equals( "-a" ) ) {

          action =  args[++i];

        } else if ( args[i].equals( "-d" ) ) {

          docid =  args[++i];

        } else if ( args[i].equals( "-t" ) ) {

          showRuntime = true;

        } else if ( args[i].equals( "-old" ) ) {

          useOldReadAlgorithm = true;

        } else {

          System.err.println

            ( "   args[" +i+ "] '" +args[i]+ "' ignored." );

        }

      }

      // Check if the required arguments are provided

      boolean argsAreValid = false;

      if (action != null) {

        if (action.equals("INSERT")) {

          if (filename != null) {

            argsAreValid = true;

          } 

        } else if (action.equals("UPDATE")) {

          if ((filename != null) && (docid != null)) {

            argsAreValid = true;

          } 

        } else if (action.equals("DELETE")) {

          if (docid != null) {

            argsAreValid = true;

          } 

        } else if (action.equals("READ")) {

          if (docid != null) {

            argsAreValid = true;

          } 

        } 

      } 

      // Print usage message if the arguments are not valid

      if (!argsAreValid) {

        System.err.println("Wrong number of arguments!!!");

        System.err.println(

          "USAGE: java DocumentImpl [-t] <-a INSERT> [-d docid] <-f filename>");

        System.err.println(

          "   OR: java DocumentImpl [-t] <-a UPDATE -d docid -f filename>");

        System.err.println(

          "   OR: java DocumentImpl [-t] <-a DELETE -d docid>");

        System.err.println(

          "   OR: java DocumentImpl [-t] [-old] <-a READ -d docid>");

        return;

      }

      // Time the request if asked for

      double startTime = System.currentTimeMillis();