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/**
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* '$RCSfile$'
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* Purpose: A Class that creates an XML text document
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* from a query to a relational DB containing a DOM representation
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* Copyright: 2000 Regents of the University of California and the
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* National Center for Ecological Analysis and Synthesis
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* Authors: Matt Jones
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* Release: @release@
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*
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* '$Author: jones $'
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* '$Date: 2000-08-21 14:52:48 -0700 (Mon, 21 Aug 2000) $'
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* '$Revision: 388 $'
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*/
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package edu.ucsb.nceas.metacat;
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import java.sql.*;
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import java.io.PrintWriter;
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import java.util.TreeSet;
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/**
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* A Class that creates an XML text document
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* from a query to a relational DB containing a DOM representation
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*/
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public class DBReader {
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private Connection conn = null;
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/**
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* main routine used for testing.
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* <p>
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* Usage: java DBReader <docid>
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*
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* @param nodeid the id number of the root of the subtree to display
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*/
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static public void main(String[] args) {
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if (args.length < 1)
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{
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System.err.println("Wrong number of arguments!!!");
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System.err.println("USAGE: java DBReader <docid>");
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return;
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} else {
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try {
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String docid = args[0];
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// Open a connection to the database
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MetaCatUtil util = new MetaCatUtil();
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Connection dbconn = util.openDBConnection();
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DBReader rd = new DBReader( dbconn );
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String xml = rd.readXMLDocument(docid);
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System.out.println(xml);
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} catch (McdbException me) {
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me.toXml(new PrintWriter(System.err));
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} catch (Exception e) {
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System.err.println("EXCEPTION HANDLING REQUIRED");
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System.err.println(e.getMessage());
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e.printStackTrace(System.err);
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}
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}
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}
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/**
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* construct a DBReader instance.
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*
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* Generally, one calls readXMLDocument() after constructing the instance
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*
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* @param conn the database connection from which to read the document
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*/
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public DBReader( Connection conn )
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{
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this.conn = conn;
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}
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/**
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* Create an XML document from the database for the document with ID docid
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*
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* @param docid the document identifier that we want retrieved
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*/
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public String readXMLDocument(String docid)
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throws McdbException
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{
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try {
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StringBuffer doc = new StringBuffer();
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// Look up the document information
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DoctypeInfo dti = getDoctypeInfo(docid);
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String docname = dti.getDocname();
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String doctype = dti.getDoctype();
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String sysid = dti.getSystemID();
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long rootnodeid = dti.getRootNodeID();
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// Download all of the document nodes using a single SQL query
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TreeSet nodeRecordList = getNodeRecordList(docid);
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// Create the elements from the downloaded nodes
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//ElementNode element = new ElementNode(conn, rootnodeid);
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ElementNode element = new ElementNode(nodeRecordList, rootnodeid);
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// Append the resulting document to the StringBuffer
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doc.append("<?xml version=\"1.0\"?>\n");
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if (docname != null) {
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if ((doctype != null) && (sysid != null)) {
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doc.append("<!DOCTYPE " + docname + " PUBLIC \"" + doctype +
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"\" \"" + sysid + "\">\n");
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} else {
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doc.append("<!DOCTYPE " + docname + ">\n");
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}
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}
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doc.append(element.toString());
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return (doc.toString());
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} catch (McdbException ex) {
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throw ex;
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} catch (Throwable t) {
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throw new McdbException("Error reading document " + docid + ".");
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}
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}
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/**
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* Look up the document type information from the database
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*
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* @param docid the id of the document to look up
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*/
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public DoctypeInfo getDoctypeInfo(String docid)
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throws McdbException
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{
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PreparedStatement pstmt;
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String doctype = null;
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String docname = null;
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String sysid = null;
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long rootnodeid = 0;
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DoctypeInfo dti = null;
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try {
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pstmt =
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conn.prepareStatement("SELECT docname,doctype,rootnodeid " +
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"FROM xml_documents " +
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"WHERE docid = ?");
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// Bind the values to the query
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pstmt.setString(1, docid);
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pstmt.execute();
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ResultSet rs = pstmt.getResultSet();
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boolean tableHasRows = rs.next();
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if (tableHasRows) {
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docname = rs.getString(1);
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doctype = rs.getString(2);
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rootnodeid = rs.getLong(3);
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}
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pstmt.close();
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if (doctype != null) {
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pstmt =
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conn.prepareStatement("SELECT system_id " +
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"FROM xml_catalog " +
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"WHERE public_id = ?");
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// Bind the values to the query
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pstmt.setString(1, doctype);
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pstmt.execute();
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rs = pstmt.getResultSet();
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tableHasRows = rs.next();
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if (tableHasRows) {
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sysid = rs.getString(1);
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}
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pstmt.close();
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}
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} catch (SQLException e) {
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throw new McdbException("Error accessing database connection.", e);
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}
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if (docname != null) {
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dti = new DoctypeInfo(docname, doctype, sysid, rootnodeid);
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return dti;
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} else {
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throw new McdbDocNotFoundException("Document not found: " + docid);
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}
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}
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/**
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* Look up the node data from the database
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*
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* @param docid the id of the document to look up
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*/
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public TreeSet getNodeRecordList(String docid)
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throws McdbException
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{
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PreparedStatement pstmt;
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TreeSet nodeRecordList = new TreeSet(new NodeComparator());
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long nodeid = 0;
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long parentnodeid = 0;
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long nodeindex = 0;
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String nodetype = null;
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String nodename = null;
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String nodedata = null;
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try {
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pstmt =
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conn.prepareStatement("SELECT nodeid,parentnodeid,nodeindex, " +
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"nodetype,nodename,"+
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"replace(" +
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"replace(" +
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"replace(nodedata,'&','&') " +
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",'<','<') " +
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",'>','>') " +
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"FROM xml_nodes WHERE docid = ?");
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// Bind the values to the query
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pstmt.setString(1, docid);
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pstmt.execute();
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ResultSet rs = pstmt.getResultSet();
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boolean tableHasRows = rs.next();
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while (tableHasRows) {
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nodeid = rs.getLong(1);
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parentnodeid = rs.getLong(2);
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nodeindex = rs.getLong(3);
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nodetype = rs.getString(4);
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nodename = rs.getString(5);
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nodedata = rs.getString(6);
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// add the data to the node record list hashtable
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NodeRecord currentRecord = new NodeRecord(nodeid, parentnodeid,
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nodeindex, nodetype, nodename, nodedata);
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nodeRecordList.add(currentRecord);
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// Advance to the next node
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tableHasRows = rs.next();
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}
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pstmt.close();
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} catch (SQLException e) {
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throw new McdbException("Error accessing database connection.", e);
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}
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if (nodeRecordList != null) {
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return nodeRecordList;
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} else {
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throw new McdbException("Error getting node data: " + docid);
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}
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}
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/**
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* A utility class that encapsulates document type information
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*/
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public class DoctypeInfo {
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private String docname = null;
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private String doctype = null;
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private String system_id = null;
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private long rootnodeid;
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/**
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* Constructor
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*/
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public DoctypeInfo(String docname, String doctype,
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String system_id, long rootnodeid) {
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this.docname = docname;
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this.doctype = doctype;
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this.system_id = system_id;
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this.rootnodeid = rootnodeid;
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}
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/**
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* get the document name
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*/
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public String getDocname() {
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return docname;
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}
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/**
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* get the document type
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*/
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public String getDoctype() {
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return doctype;
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}
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/**
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* get the system identifier
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*/
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public String getSystemID() {
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return system_id;
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}
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/**
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* get the root node identifier
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*/
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public long getRootNodeID() {
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return rootnodeid;
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}
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}
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}
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