Merge pull request #19 from hartig/GenericServlet

Servlet now completely agnostic of the type of LDFs requested

Author: mielvds

WebContent/WEB-INF/web.xml

@@ -4,7 +4,7 @@
     <servlet>
         <display-name>BasicLdfServlet</display-name>
         <servlet-name>BasicLdfServlet</servlet-name>
-        <servlet-class>org.linkeddatafragments.servlet.TriplePatternFragmentServlet</servlet-class>
+        <servlet-class>org.linkeddatafragments.servlet.LinkedDataFragmentServlet</servlet-class>
     </servlet>
     <servlet-mapping>
         <servlet-name>BasicLdfServlet</servlet-name>

src/org/linkeddatafragments/datasource/DataSource.java

@@ -1,5 +1,12 @@
 package org.linkeddatafragments.datasource;
 
+import javax.servlet.http.HttpServletRequest;
+
+import org.linkeddatafragments.config.ConfigReader;
+import org.linkeddatafragments.fragments.LinkedDataFragmentRequest;
+import org.linkeddatafragments.fragments.tpf.TriplePatternFragmentRequest;
+import org.linkeddatafragments.fragments.tpf.TriplePatternFragmentRequestImpl;
+
 /**
  *
  * @author mielvandersande
@@ -24,6 +31,24 @@ public String getTitle() {
         return this.title;
     };
 
+    /**
+     * This implementation assumes that the given request is a
+     * {@link TriplePatternFragmentRequest}.
+     *
+     * Data sources for other types of {@link LinkedDataFragmentRequest}s must
+     * override this method accordingly.
+     */
+    @Override
+    public IFragmentRequestProcessor getRequestProcessor(
+            final HttpServletRequest request,
+            final ConfigReader config )
+    {
+        final TriplePatternFragmentRequest r =
+                new TriplePatternFragmentRequestImpl( request, config );
+
+        return getRequestProcessor( r );
+    }
+
     @Override
     public void close() {}
 }

src/org/linkeddatafragments/datasource/IDataSource.java

@@ -2,6 +2,9 @@
 
 import java.io.Closeable;
 
+import javax.servlet.http.HttpServletRequest;
+
+import org.linkeddatafragments.config.ConfigReader;
 import org.linkeddatafragments.fragments.LinkedDataFragmentRequest;
 
 /**
@@ -16,6 +19,14 @@ public interface IDataSource extends Closeable {
 
     public String getDescription();
 
+    /**
+     * Returns a data source specific processor for the given request of a
+     * Linked Data Fragment.
+     */
+    IFragmentRequestProcessor getRequestProcessor(
+            final HttpServletRequest request,
+            final ConfigReader config );
+
     /**
      * Returns a data source specific processor for the given request of a
      * Linked Data Fragment.

src/org/linkeddatafragments/fragments/tpf/TriplePatternFragmentImpl.java

@@ -1,14 +1,17 @@
 package org.linkeddatafragments.fragments.tpf;
 
+import java.util.NoSuchElementException;
+
 import org.linkeddatafragments.fragments.LinkedDataFragmentBase;
 import org.linkeddatafragments.util.CommonResources;
 
 import com.hp.hpl.jena.datatypes.xsd.XSDDatatype;
 import com.hp.hpl.jena.rdf.model.Literal;
 import com.hp.hpl.jena.rdf.model.Model;
-import com.hp.hpl.jena.rdf.model.ModelFactory;
 import com.hp.hpl.jena.rdf.model.Resource;
+import com.hp.hpl.jena.rdf.model.Statement;
 import com.hp.hpl.jena.rdf.model.StmtIterator;
+import com.hp.hpl.jena.util.iterator.NiceIterator;
 
 /**
  * Implementation of {@link TriplePatternFragment}.
@@ -52,13 +55,16 @@ public TriplePatternFragmentImpl( Model triples,
                                       final long pageNumber,
                                       final boolean isLastPage ) {
         super( fragmentURL, datasetURL, pageNumber, isLastPage );
-        this.triples = triples == null ? ModelFactory.createDefaultModel() : triples;
+        this.triples = triples;
         this.totalSize = totalSize < 0 ? 0 : totalSize;
     }
 
     @Override
     public StmtIterator getTriples() {
-        return triples.listStatements();
+        if ( triples != null )
+            return triples.listStatements();
+        else
+            return emptyStmtIterator;
     }
 
     @Override
@@ -119,4 +125,14 @@ public String getTemplate() {
                TriplePatternFragmentRequest.PARAMETERNAME_OBJ + "}";
     }
 
+
+    public static final StmtIterator emptyStmtIterator = new EmptyStmtIterator();
+
+    public static class EmptyStmtIterator
+        extends NiceIterator<Statement>
+        implements StmtIterator
+    {
+        public Statement nextStatement() { throw new NoSuchElementException(); }
+    }
+
 }

src/org/linkeddatafragments/servlet/TriplePatternFragmentServlet.java renamed to src/org/linkeddatafragments/servlet/LinkedDataFragmentServlet.java

@@ -28,9 +28,7 @@
 import org.linkeddatafragments.exceptions.DataSourceException;
 import org.linkeddatafragments.exceptions.DataSourceNotFoundException;
 import org.linkeddatafragments.fragments.LinkedDataFragment;
-import org.linkeddatafragments.fragments.LinkedDataFragmentRequest;
 import org.linkeddatafragments.fragments.LinkedDataFragmentRequestBase;
-import org.linkeddatafragments.fragments.tpf.TriplePatternFragmentRequestImpl;
 import org.linkeddatafragments.util.MIMEParse;
 
 /**
@@ -40,7 +38,7 @@
  * @author Bart Hanssens
  * @author <a href="http://olafhartig.de">Olaf Hartig</a>
  */
-public class TriplePatternFragmentServlet extends HttpServlet {
+public class LinkedDataFragmentServlet extends HttpServlet {
 
     private final static long serialVersionUID = 1L;
 
@@ -51,7 +49,7 @@ public class TriplePatternFragmentServlet extends HttpServlet {
     private final HashMap<String, IDataSource> dataSources = new HashMap<>();
     private final Collection<String> mimeTypes = new ArrayList<>();
 
-    public TriplePatternFragmentServlet() {
+    public LinkedDataFragmentServlet() {
         HdtDataSourceType.register();
         JenaTDBDataSourceType.register();
     }
@@ -141,8 +139,7 @@ private IDataSource getDataSource(HttpServletRequest request) throws DataSourceN
     public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException {
         try {
             IDataSource dataSource = getDataSource(request);
-            final LinkedDataFragmentRequest ldfRequest = new TriplePatternFragmentRequestImpl( request, config );
-            final IFragmentRequestProcessor processor = dataSource.getRequestProcessor( ldfRequest );
+            final IFragmentRequestProcessor processor = dataSource.getRequestProcessor( request, config );
             final LinkedDataFragment fragment = processor.createRequestedFragment();
 
             final Model output = ModelFactory.createDefaultModel();

src/org/linkeddatafragments/standalone/JettyServer.java

@@ -10,7 +10,7 @@
 import org.eclipse.jetty.servlet.ServletHandler;
 import org.eclipse.jetty.servlet.ServletHolder;
 
-import org.linkeddatafragments.servlet.TriplePatternFragmentServlet;
+import org.linkeddatafragments.servlet.LinkedDataFragmentServlet;
 
 /**
  * <p>
@@ -64,8 +64,8 @@ public static void main(String[] args) throws Exception {
         server.setHandler(handler);
 
         // add the TriplePatternFragmentsServlet to the handler
-        ServletHolder tpfServletHolder = new ServletHolder(new TriplePatternFragmentServlet());
-        tpfServletHolder.setInitParameter(TriplePatternFragmentServlet.CFGFILE, config);
+        ServletHolder tpfServletHolder = new ServletHolder(new LinkedDataFragmentServlet());
+        tpfServletHolder.setInitParameter(LinkedDataFragmentServlet.CFGFILE, config);
         handler.addServletWithMapping(tpfServletHolder, "/*");
 
         // start the server