added an interface and classes for parsing HTTP requests into LinkedDataFragmentRequest objects

Author: Olaf Hartig

src/org/linkeddatafragments/fragments/FragmentRequestParserBase.java

@@ -0,0 +1,92 @@
+package org.linkeddatafragments.fragments;
+
+import javax.servlet.http.HttpServletRequest;
+
+import org.linkeddatafragments.config.ConfigReader;
+
+/**
+ * Base class for implementations of {@link IFragmentRequestParser}.
+ *
+ * @author <a href="http://olafhartig.de">Olaf Hartig</a>
+ */
+abstract public class FragmentRequestParserBase implements IFragmentRequestParser
+{
+    @Override
+    final public LinkedDataFragmentRequest parseIntoFragmentRequest(
+            final HttpServletRequest httpRequest,
+            final ConfigReader config )
+                    throws IllegalArgumentException
+    {
+        return getWorker( httpRequest, config ).createFragmentRequest();
+    }
+
+    abstract protected Worker getWorker( final HttpServletRequest httpRequest,
+                                         final ConfigReader config )
+                                               throws IllegalArgumentException;
+
+
+    abstract static protected class Worker
+    {
+        public final HttpServletRequest request;
+        public final ConfigReader config;
+
+        public final boolean pageNumberWasRequested;
+        public final long pageNumber;
+        
+        public Worker( final HttpServletRequest request,
+                       final ConfigReader config )
+        {
+            this.request = request;
+            this.config = config;
+            
+            final String givenPageNumber = request.getParameter(
+                              LinkedDataFragmentRequest.PARAMETERNAME_PAGE );
+            if ( givenPageNumber != null ) {
+                long pageNumber;
+                try {
+                    pageNumber = Long.parseLong( givenPageNumber );
+                } catch (NumberFormatException ex) {
+                    pageNumber = 1L;
+                }
+                this.pageNumber = ( pageNumber > 0 ) ? pageNumber : 1L;
+                this.pageNumberWasRequested = true;
+            }
+            else {
+                this.pageNumber = 1L;
+                this.pageNumberWasRequested = false;
+            }
+        }
+
+        abstract public LinkedDataFragmentRequest createFragmentRequest()
+                                               throws IllegalArgumentException;
+
+        public String getFragmentURL() {
+            final String datasetURL = getDatasetURL();
+            final String query = request.getQueryString();
+            return query == null ? datasetURL : (datasetURL + "?" + query);
+        }
+
+        public String getDatasetURL() {
+            return extractBaseURL( request, config ) + request.getRequestURI();
+        }
+
+    } // end of class Worker
+
+
+    // ----- HELPERS ---------
+
+    public static String extractBaseURL( final HttpServletRequest request,
+                                         final ConfigReader config ) {
+        if (config.getBaseURL() != null) {
+            return config.getBaseURL();
+        } else if ((request.getServerPort() == 80)
+                || (request.getServerPort() == 443)) {
+            return request.getScheme() + "://"
+                    + request.getServerName();
+        } else {
+            return request.getScheme() + "://"
+                    + request.getServerName() + ":" + request.getServerPort();
+        }
+    }
+
+}

src/org/linkeddatafragments/fragments/IFragmentRequestParser.java

@@ -0,0 +1,26 @@
+package org.linkeddatafragments.fragments;
+
+import javax.servlet.http.HttpServletRequest;
+
+import org.linkeddatafragments.config.ConfigReader;
+
+/**
+ * Parses HTTP requests into specific {@link LinkedDataFragmentRequest}s.
+ *
+ * @author <a href="http://olafhartig.de">Olaf Hartig</a>
+ */
+public interface IFragmentRequestParser
+{
+    /**
+     * Parses the given HTTP request into a specific
+     * {@link LinkedDataFragmentRequest}.
+     *
+     * @throws IllegalArgumentException
+     *         If the given HTTP request cannot be interpreted (perhaps due to
+     *         missing request parameters).  
+     */
+    LinkedDataFragmentRequest parseIntoFragmentRequest(
+            final HttpServletRequest httpRequest,
+            final ConfigReader config )
+                    throws IllegalArgumentException;
+}

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

@@ -0,0 +1,63 @@
+package org.linkeddatafragments.fragments.tpf;
+
+import javax.servlet.http.HttpServletRequest;
+
+import org.linkeddatafragments.config.ConfigReader;
+import org.linkeddatafragments.fragments.FragmentRequestParserBase;
+import org.linkeddatafragments.fragments.IFragmentRequestParser;
+import org.linkeddatafragments.fragments.LinkedDataFragmentRequest;
+
+/**
+ * An {@link IFragmentRequestParser} for {@link TriplePatternFragmentRequest}s.
+ *
+ * @author <a href="http://olafhartig.de">Olaf Hartig</a>
+ */
+public class TPFRequestParser extends FragmentRequestParserBase
+{
+    @Override
+    protected Worker getWorker( final HttpServletRequest httpRequest,
+                                final ConfigReader config )
+                                               throws IllegalArgumentException
+    {
+        return new Worker( httpRequest, config );
+    }
+
+
+    static protected class Worker extends FragmentRequestParserBase.Worker
+    {   
+        public Worker( final HttpServletRequest request,
+                       final ConfigReader config )
+        {
+            super( request, config );
+        }
+
+        public LinkedDataFragmentRequest createFragmentRequest()
+                                               throws IllegalArgumentException
+        {
+            return new TriplePatternFragmentRequestImpl( getFragmentURL(),
+                                                         getDatasetURL(),
+                                                         pageNumberWasRequested,
+                                                         pageNumber,
+                                                         getSubject(),
+                                                         getPredicate(),
+                                                         getObject() );
+        }
+
+        public String getSubject() {
+            return request.getParameter(
+                    TriplePatternFragmentRequest.PARAMETERNAME_SUBJ );
+        }
+
+        public String getPredicate() {
+            return request.getParameter(
+                    TriplePatternFragmentRequest.PARAMETERNAME_PRED );
+        }
+
+        public String getObject() {
+            return request.getParameter(
+                    TriplePatternFragmentRequest.PARAMETERNAME_OBJ );
+        }
+
+    } // end of class Worker
+
+}