1 | /******************************************************************************* |
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2 | * Copyright (c) 2008 Cambridge Semantics Incorporated. |
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3 | * All rights reserved. This program and the accompanying materials |
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4 | * are made available under the terms of the Eclipse Public License v1.0 |
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5 | * which accompanies this distribution, and is available at |
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6 | * http://www.eclipse.org/legal/epl-v10.html |
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7 | * |
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8 | * Contributors: |
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9 | * Cambridge Semantics Incorporated |
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10 | *******************************************************************************/ |
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11 | package org.isocat.relcat.openanzo; |
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12 | |
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13 | import java.util.ArrayList; |
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14 | import java.util.Collection; |
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15 | import java.util.Collections; |
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16 | import java.util.Comparator; |
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17 | |
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18 | import org.apache.commons.lang.builder.CompareToBuilder; |
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19 | import org.openanzo.rdf.Statement; |
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20 | import org.openanzo.rdf.URI; |
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21 | import org.openanzo.rdf.vocabulary.RDF; |
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22 | |
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23 | /** |
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24 | * Sorts statements by named graph, then subject, pred, obj. This sorting results in well framed serialized rdf. |
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25 | * |
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26 | * @author Joe Betz <jpbetz@cambridgesemantics.com> |
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27 | * |
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28 | */ |
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29 | class StatementComparator implements Comparator<Statement> { |
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30 | |
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31 | private static StatementComparator statementComparator = new StatementComparator(); |
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32 | |
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33 | private static PredicateComparator predicateComparator = new PredicateComparator(); |
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34 | |
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35 | public static Collection<Statement> sort(Collection<Statement> stmt) { |
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36 | ArrayList<Statement> list = new ArrayList<Statement>(stmt); |
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37 | Collections.sort(list, statementComparator); |
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38 | return list; |
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39 | } |
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40 | |
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41 | public int compare(Statement o1, Statement o2) { |
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42 | CompareToBuilder builder = new CompareToBuilder(); |
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43 | builder.append(o1.getNamedGraphUri() != null ? o1.getNamedGraphUri().toString() : null, o2.getNamedGraphUri() != null ? o2.getNamedGraphUri().toString() : null); |
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44 | builder.append(o1.getSubject().toString(), o2.getSubject().toString()); |
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45 | builder.append(o1.getPredicate(), o2.getPredicate(), predicateComparator); |
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46 | builder.append(o1.getObject().toString(), o2.getObject().toString()); |
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47 | return builder.toComparison(); |
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48 | } |
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49 | |
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50 | /** |
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51 | * This sort URIs in lexical order except for the rdf:type uri, which it always sorts before any other URI. This makes the serialization of RDF simpler to |
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52 | * read since it's typically easier to read when the type assertions for a resource come first, before other properties. |
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53 | * |
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54 | * The rdf:type URI is specifically <code>http://www.w3.org/1999/02/22-rdf-syntax-ns#type</code>. |
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55 | * |
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56 | * @author Jordi Albornoz Mulligan <jordi@cambridgesemantics.com> |
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57 | */ |
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58 | public static class PredicateComparator implements Comparator<URI> { |
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59 | public int compare(URI o1, URI o2) { |
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60 | int ret; |
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61 | if (o1.equals(o2)) { |
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62 | ret = 0; |
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63 | } else if (o1.equals(RDF.TYPE)) { |
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64 | ret = -1; |
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65 | } else if (o2.equals(RDF.TYPE)) { |
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66 | ret = 1; |
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67 | } else { |
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68 | ret = o1.compareTo(o2); |
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69 | } |
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70 | return ret; |
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71 | } |
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72 | } |
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73 | } |
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