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/**
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* '$RCSfile$'
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* Purpose: A class to asyncronously build the package relation index
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* in the database table xml_relation.
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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: Chad Berkley
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* Release: @release@
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*
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* '$Author: berkley $'
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* '$Date: 2000-11-09 14:04:32 -0800 (Thu, 09 Nov 2000) $'
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* '$Revision: 524 $'
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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.util.*;
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import java.lang.Thread;
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public class RelationHandler implements Runnable
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{
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private Thread btThread = null;
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private Connection conn = null;
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private DocumentImpl xmldoc = null;
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MetaCatUtil util = new MetaCatUtil();
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/**
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* Constructor for this class. finds all of the relations to a single xml
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* document and writes them to the database. This includes transitive
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* relations.
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* @param xmldoc the xml document to index.
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*/
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public RelationHandler(DocumentImpl xmldoc, Connection conn)
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{
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this.conn = conn;
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this.xmldoc = xmldoc;
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if(xmldoc.getDoctype().equals(util.getOption("packagedoctype")))
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{ //make sure this doctype is a package document then run the thread
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btThread = new Thread(this);
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btThread.setPriority(Thread.MIN_PRIORITY);
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btThread.start();
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}
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}
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/**
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* The thread handler
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*/
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public void run()
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{
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//pseudo-code algorithm
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//for each new relation r in xml_nodes
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// put r into xml_relation
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// compare r to each relation already in xml_relation
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// if r isrelatedto a row in xml_relation
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// add a new row to xml_relation that represents this new relation
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try
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{
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String docid = xmldoc.getDocID();
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PreparedStatement pstmt = conn.prepareStatement(
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QuerySpecification.printPackageSQL(docid));
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pstmt.execute();
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//get the new relations out of xml_nodes
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ResultSet rs = pstmt.getResultSet();
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boolean hasmorerows = rs.next();
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while(hasmorerows)
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{
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String subject = rs.getString(1);
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MetacatURL subjectMurl = new MetacatURL(subject);
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String subjectDoctype = null;
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if(subjectMurl.getURLType().equals("metacat"))
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{
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DocumentImpl subDoc = new DocumentImpl(conn,
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subjectMurl.getParam(0)[1]);
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subjectDoctype = subDoc.getDoctype();
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}
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String relationship = rs.getString(2);
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String object = rs.getString(3);
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//compare r to each relation in xml_relation
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pstmt = conn.prepareStatement("select subject, subdoctype, " +
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"relationship, object, objdoctype " +
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"from xml_relation");
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pstmt.execute();
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//get each relation in xml_relation for comparison
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ResultSet relations = pstmt.getResultSet();
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boolean hasmorerelations = relations.next();
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while(hasmorerelations)
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{
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String currentSub = relations.getString(1);
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String currentSubDoctype = relations.getString(2);
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String currentRelationship = relations.getString(3);
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String currentObj = relations.getString(4);
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String currentObjDoctype = relations.getString(5);
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if(object.equals(currentObj))
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{//there is a transitive relation so add a new relation to the table
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StringBuffer insertTransRelation = new StringBuffer();
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insertTransRelation.append("insert into xml_relation (subject, ");
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insertTransRelation.append("subdoctype, relationship, object, ");
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insertTransRelation.append("objdoctype) values ('");
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insertTransRelation.append(currentSub).append("', '");
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insertTransRelation.append(currentSubDoctype).append("', ");
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insertTransRelation.append("'hasTransitiveRelationTo', '");
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insertTransRelation.append(subject).append("', '");
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insertTransRelation.append(subjectDoctype).append("')");
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pstmt = conn.prepareStatement(insertTransRelation.toString());
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pstmt.execute();
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insertTransRelation = new StringBuffer();
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//put the same relation in with the subject and object switched
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insertTransRelation.append("insert into xml_relation (subject, ");
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insertTransRelation.append("subdoctype, relationship, object, ");
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insertTransRelation.append("objdoctype) values ('");
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insertTransRelation.append(subject).append("', '");
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insertTransRelation.append(subjectDoctype).append("', ");
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insertTransRelation.append("'hasTransitiveRelationTo', '");
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insertTransRelation.append(currentSub).append("', '");
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insertTransRelation.append(currentSubDoctype).append("')");
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pstmt = conn.prepareStatement(insertTransRelation.toString());
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pstmt.execute();
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}
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hasmorerelations = relations.next();
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}
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//get the current relations information
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MetacatURL subMurl = new MetacatURL(subject);
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MetacatURL objMurl = new MetacatURL(object);
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String subDoctype = null;
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String objDoctype = null;
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if(subMurl.getURLType().equals("metacat"))
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{
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DocumentImpl subDoc = new DocumentImpl(conn, subMurl.getParam(0)[1]);
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subDoctype = subDoc.getDoctype();
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}
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if(objMurl.getURLType().equals("metacat"))
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{
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DocumentImpl objDoc = new DocumentImpl(conn, objMurl.getParam(0)[1]);
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objDoc.getDoctype();
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}
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//now that the comparisons are done, the new relation can be put
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//into xml_relation
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StringBuffer insertStmt = new StringBuffer();
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insertStmt.append("insert into xml_relation (subject, subdoctype, ");
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insertStmt.append("relationship, object, objdoctype) values ('");
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insertStmt.append(subject).append("', '");
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insertStmt.append(subDoctype).append("', '");
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insertStmt.append(relationship).append("', '");
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insertStmt.append(object).append("', '");
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insertStmt.append(objDoctype).append("')");
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pstmt = conn.prepareStatement(insertStmt.toString());
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pstmt.execute();
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hasmorerows = rs.next();
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}
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conn.commit();
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btThread = null;
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} catch(Exception e) {
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try {
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conn.rollback();
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} catch (SQLException sqle) {}
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System.out.println("Error in relationHandler: " + e.getMessage());
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util.debugMessage("Error in relationHandler: " + e.getMessage());
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e.printStackTrace(System.out);
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btThread = null;
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}
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}
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}
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