Initial support for jena TDB

Author: barthanssens

pom.xml

@@ -68,6 +68,11 @@
             <version>2.6</version>
             <type>jar</type>
         </dependency>
+        <dependency>
+            <groupId>org.apache.jena</groupId>
+            <artifactId>jena-tdb</artifactId>
+            <version>1.1.2</version>
+        </dependency>
     </dependencies>
     <build>
         <sourceDirectory>src</sourceDirectory>

src/org/linkeddatafragments/datasource/DataSource.java

@@ -3,11 +3,26 @@
 /**
  *
  * @author mielvandersande
+ * @author Bart Hanssens
  */
 public abstract class DataSource implements IDataSource {
     protected String title;
     protected String description; 
 
+    /**
+     * 
+     * @param offset
+     * @param limit 
+     */
+    protected void checkBoundaries(long offset, long limit) {
+        if (offset < 0) {
+            throw new IndexOutOfBoundsException("offset");
+        }
+        if (limit < 1) {
+            throw new IllegalArgumentException("limit");
+        }
+    }
+    
     public DataSource(String title, String description) {
         this.title = title;
         this.description = description;

src/org/linkeddatafragments/datasource/DataSourceFactory.java

@@ -9,8 +9,11 @@
 /**
  *
  * @author Miel Vander Sande
+ * @author Bart Hanssens
  */
 public class DataSourceFactory {
+    public final static String HDT = "HdtDatasource";
+    public final static String JENA_TDB = "JenaTDBDatasource";
 
     public static IDataSource create(JsonObject config) throws DataSourceException {
         String title = config.getAsJsonPrimitive("type").getAsString();
@@ -20,14 +23,18 @@ public static IDataSource create(JsonObject config) throws DataSourceException {
         JsonObject settings = config.getAsJsonObject("settings");
 
         switch (type) {
-            case "HdtDatasource":
-                File file = new File(settings.getAsJsonPrimitive("file").getAsString());
-                
+            case HDT:
                 try {
+                    File file = new File(settings.getAsJsonPrimitive("file").getAsString());
                     return new HdtDataSource(title, description, file.getAbsolutePath());
                 } catch (IOException ex) {
                     throw new DataSourceException(ex);
                 }
+                
+            case JENA_TDB:                
+                File file = new File(settings.getAsJsonPrimitive("directory").getAsString());
+                return new JenaTDBDataSource(title, description, file);
+                
             default:
                 throw new UnknownDataSourceTypeException(type);
 

src/org/linkeddatafragments/datasource/HdtDataSource.java

@@ -42,12 +42,7 @@ public HdtDataSource(String title, String description, String hdtFile) throws IO
 
     @Override
     public TriplePatternFragment getFragment(Resource subject, Property predicate, RDFNode object, final long offset, final long limit) {
-        if (offset < 0) {
-            throw new IndexOutOfBoundsException("offset");
-        }
-        if (limit < 1) {
-            throw new IllegalArgumentException("limit");
-        }
+        checkBoundaries(offset, limit);
 
         // look up the result from the HDT datasource)
         int subjectId = subject == null ? 0 : dictionary.getIntID(subject.asNode(), TripleComponentRole.SUBJECT);
@@ -88,9 +83,13 @@ public TriplePatternFragment getFragment(Resource subject, Property predicate, R
             }
         }
 
-        // estimates can be wrong; ensure 0 is returned if there are no results, and always more than actual results
-        final long estimatedTotal = triples.size() > 0 ? Math.max(offset + triples.size() + 1, matches.estimatedNumResults())
-                : hasMatches ? Math.max(matches.estimatedNumResults(), 1) : 0;
+        // estimates can be wrong; ensure 0 is returned if there are no results, 
+        // and always more than actual results
+        final long estimatedTotal = triples.size() > 0 
+                ? Math.max(offset + triples.size() + 1, matches.estimatedNumResults())
+                : hasMatches 
+                    ? Math.max(matches.estimatedNumResults(), 1) 
+                    : 0;
 
         // create the fragment
         return new TriplePatternFragment() {

src/org/linkeddatafragments/datasource/JenaTDBDataSource.java

@@ -0,0 +1,74 @@
+package org.linkeddatafragments.datasource;
+
+import com.hp.hpl.jena.query.Dataset;
+import com.hp.hpl.jena.query.Query;
+import com.hp.hpl.jena.query.QueryExecution;
+import com.hp.hpl.jena.query.QueryExecutionFactory;
+import com.hp.hpl.jena.query.QueryFactory;
+import com.hp.hpl.jena.query.QuerySolutionMap;
+import com.hp.hpl.jena.query.ReadWrite;
+import com.hp.hpl.jena.query.Syntax;
+import com.hp.hpl.jena.rdf.model.Model;
+import com.hp.hpl.jena.rdf.model.ModelFactory;
+import com.hp.hpl.jena.rdf.model.Property;
+import com.hp.hpl.jena.rdf.model.RDFNode;
+import com.hp.hpl.jena.rdf.model.Resource;
+import com.hp.hpl.jena.tdb.TDBFactory;
+import java.io.File;
+
+/**
+ * Experimental Jena TDB-backed data source of Basic Linked Data Fragments.
+ * 
+ * @author Bart Hanssens <bart.hanssens@fedict.be>
+ */
+public class JenaTDBDataSource extends DataSource {
+    private final Dataset tdb;
+    private final String sparql = "CONSTRUCT ?s ?p ?o " +
+                                  "ORDER BY ?s ?p ?o";
+    private final Query query = QueryFactory.create(sparql, Syntax.syntaxSPARQL_11);
+    
+    @Override
+    public TriplePatternFragment getFragment(Resource subject, Property predicate, RDFNode object, long offset, long limit) {
+        checkBoundaries(offset, limit);
+        
+        tdb.begin(ReadWrite.READ);
+        
+        Model model = tdb.getDefaultModel();
+        QuerySolutionMap map = new QuerySolutionMap();
+        map.add("s", subject);
+        map.add("p", predicate);
+        map.add("o", object);
+        
+        query.setOffset(offset);
+        query.setLimit(limit);
+        
+        QueryExecution qexec = QueryExecutionFactory.create(query, model);
+        final Model triples = ModelFactory.createDefaultModel();
+        qexec.execConstruct(triples);
+        
+        tdb.end();
+
+        if (triples.isEmpty()) {
+            return new TriplePatternFragmentBase();
+        } else {
+            // For now, fake the estimate
+            long size = triples.size();
+            long estimate = (size == limit) ? offset + limit + 1 : offset + size;
+  
+            return new TriplePatternFragmentBase(triples, estimate);
+        }
+    }
+    
+    
+    /**
+     * Constructor
+     * 
+     * @param title
+     * @param description
+     * @param tdbdir directory used for TDB backing
+     */
+    public JenaTDBDataSource(String title, String description, File tdbdir) {
+        super(title, description);
+        this.tdb = TDBFactory.createDataset(tdbdir.getAbsolutePath());
+    }
+}