Load data source types based on config file

config-example.json

@@ -1,6 +1,11 @@
 {
   "title": "My Linked Data Fragments server",
 
+  "datasourcetypes": {
+    "HdtDatasource"       : "org.linkeddatafragments.datasource.hdt.HdtDataSourceType",
+    "JenaTDBDatasource"   : "org.linkeddatafragments.datasource.tdb.JenaTDBDataSourceType"
+  },
+
   "datasources": {
     "dbpedia": {
       "title": "DBPedia",

src/org/linkeddatafragments/config/ConfigReader.java

@@ -5,6 +5,8 @@
 import java.util.Map;
 import java.util.Map.Entry;
 
+import org.linkeddatafragments.datasource.IDataSourceType;
+
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.google.gson.JsonParser;
@@ -13,8 +15,10 @@
  * Reads the configuration of a Linked Data Fragments server.
  *
  * @author Ruben Verborgh
+ * @author <a href="http://olafhartig.de">Olaf Hartig</a>
  */
 public class ConfigReader {
+    private final Map<String, IDataSourceType> dataSourceTypes = new HashMap<>();
     private final Map<String, JsonObject> dataSources = new HashMap<>();
     private final Map<String, String> prefixes = new HashMap<>();
     private final String baseURL;
@@ -28,6 +32,10 @@ public ConfigReader(Reader configReader) {
         JsonObject root = new JsonParser().parse(configReader).getAsJsonObject();
         this.baseURL = root.has("baseURL") ? root.getAsJsonPrimitive("baseURL").getAsString() : null;
 
+        for (Entry<String, JsonElement> entry : root.getAsJsonObject("datasourcetypes").entrySet()) {
+            final String className = entry.getValue().getAsString();
+            dataSourceTypes.put(entry.getKey(), initDataSouceType(className) );
+        }
         for (Entry<String, JsonElement> entry : root.getAsJsonObject("datasources").entrySet()) {
             JsonObject dataSource = entry.getValue().getAsJsonObject();
             this.dataSources.put(entry.getKey(), dataSource);
@@ -37,6 +45,15 @@ public ConfigReader(Reader configReader) {
         }
     }
 
+    /**
+     * Gets the data source types.
+     *
+     * @return a mapping of names of data source types to these types  
+     */
+    public Map<String, IDataSourceType> getDataSourceTypes() {
+        return dataSourceTypes;
+    }
+
     /**
      * Gets the data sources.
      *
@@ -58,4 +75,35 @@ public Map<String, String> getPrefixes() {
     public String getBaseURL() {
         return baseURL;
     }
+
+    protected IDataSourceType initDataSouceType( final String className )
+    {
+        final Class<?> c;
+        try {
+            c = Class.forName( className ); 
+        }
+        catch ( ClassNotFoundException e ) {
+            throw new IllegalArgumentException( "Class not found: " + className,
+                                                e );
+        }
+
+        final Object o;
+        try {
+            o = c.newInstance();
+        }
+        catch ( Exception e ) {
+            throw new IllegalArgumentException(
+                        "Creating an instance of class '" + className + "' " +
+                        "caused a " + e.getClass().getSimpleName() + ": " +
+                        e.getMessage(), e );
+        }
+
+        if ( ! (o instanceof IDataSourceType) )
+            throw new IllegalArgumentException(
+                        "Class '" + className + "' is not an implementation " +
+                        "of IDataSourceType." );
+
+        return (IDataSourceType) o;
+    }
+
 }

src/org/linkeddatafragments/datasource/hdt/HdtDataSourceType.java

@@ -3,7 +3,6 @@
 import java.io.File;
 import java.io.IOException;
 
-import org.linkeddatafragments.datasource.DataSourceTypesRegistry;
 import org.linkeddatafragments.datasource.IDataSource;
 import org.linkeddatafragments.datasource.IDataSourceType;
 import org.linkeddatafragments.exceptions.DataSourceException;
@@ -17,15 +16,6 @@
  */
 public class HdtDataSourceType implements IDataSourceType
 {
-    public static final String TYPE_NAME = "HdtDatasource";
-
-    public static void register() {
-        if ( ! DataSourceTypesRegistry.isRegistered(TYPE_NAME) ) {
-            DataSourceTypesRegistry.register( TYPE_NAME,
-                                              new HdtDataSourceType() );
-        }
-    }
-
     @Override
     public IDataSource createDataSource( final String title,
                                          final String description,

src/org/linkeddatafragments/datasource/tdb/JenaTDBDataSourceType.java

@@ -2,7 +2,6 @@
 
 import java.io.File;
 
-import org.linkeddatafragments.datasource.DataSourceTypesRegistry;
 import org.linkeddatafragments.datasource.IDataSource;
 import org.linkeddatafragments.datasource.IDataSourceType;
 import org.linkeddatafragments.exceptions.DataSourceException;
@@ -17,15 +16,6 @@
  */
 public class JenaTDBDataSourceType implements IDataSourceType
 {
-    public static final String TYPE_NAME = "JenaTDBDatasource";
-
-    public static void register() {
-        if ( ! DataSourceTypesRegistry.isRegistered(TYPE_NAME) ) {
-            DataSourceTypesRegistry.register( TYPE_NAME,
-                                              new JenaTDBDataSourceType() );
-        }
-    }
-
     @Override
     public IDataSource createDataSource( final String title,
                                          final String description,

src/org/linkeddatafragments/servlet/LinkedDataFragmentServlet.java

@@ -20,11 +20,10 @@
 import org.apache.jena.riot.RDFLanguages;
 import org.linkeddatafragments.config.ConfigReader;
 import org.linkeddatafragments.datasource.DataSourceFactory;
+import org.linkeddatafragments.datasource.DataSourceTypesRegistry;
 import org.linkeddatafragments.datasource.IDataSource;
-import org.linkeddatafragments.datasource.hdt.HdtDataSourceType;
+import org.linkeddatafragments.datasource.IDataSourceType;
 import org.linkeddatafragments.datasource.index.IndexDataSource;
-import org.linkeddatafragments.datasource.tdb.JenaTDBDataSourceType;
-import org.linkeddatafragments.exceptions.DataSourceException;
 import org.linkeddatafragments.exceptions.DataSourceNotFoundException;
 import org.linkeddatafragments.fragments.FragmentRequestParserBase;
 import org.linkeddatafragments.fragments.LinkedDataFragment;
@@ -49,11 +48,6 @@ public class LinkedDataFragmentServlet extends HttpServlet {
     private final HashMap<String, IDataSource> dataSources = new HashMap<>();
     private final Collection<String> mimeTypes = new ArrayList<>();
 
-    public LinkedDataFragmentServlet() {
-        HdtDataSourceType.register();
-        JenaTDBDataSourceType.register();
-    }
-
     private File getConfigFile(ServletConfig config) throws IOException {
         String path = config.getServletContext().getRealPath("/");
         if (path == null) {
@@ -80,6 +74,13 @@ public void init(ServletConfig servletConfig) throws ServletException {
             File configFile = getConfigFile(servletConfig);
             config = new ConfigReader(new FileReader(configFile));
 
+            // register data source types
+            for ( Entry<String,IDataSourceType> typeEntry : config.getDataSourceTypes().entrySet() ) {
+                DataSourceTypesRegistry.register( typeEntry.getKey(),
+                                                  typeEntry.getValue() );
+            }
+
+            // register data sources
             for (Entry<String, JsonObject> dataSource : config.getDataSources().entrySet()) {
                 dataSources.put(dataSource.getKey(), DataSourceFactory.create(dataSource.getValue()));
             }
@@ -89,7 +90,7 @@ public void init(ServletConfig servletConfig) throws ServletException {
             mimeTypes.add(Lang.JSONLD.getHeaderString());
             mimeTypes.add(Lang.NTRIPLES.getHeaderString());
             mimeTypes.add(Lang.RDFXML.getHeaderString());
-        } catch (IOException | DataSourceException e) {
+        } catch (Exception e) {
             throw new ServletException(e);
         }
     }

src/test/java/org/linkeddatafragments/datasource/HdtDataSourceTest.java

@@ -7,6 +7,7 @@
 import org.junit.Before;
 import org.junit.BeforeClass;
 import org.linkeddatafragments.datasource.DataSourceFactory;
+import org.linkeddatafragments.datasource.DataSourceTypesRegistry;
 import org.linkeddatafragments.datasource.hdt.HdtDataSourceType;
 import org.rdfhdt.hdt.enums.RDFNotation;
 import org.rdfhdt.hdt.hdt.HDT;
@@ -24,7 +25,11 @@ public class HdtDataSourceTest extends DataSourceTest {
 
     @BeforeClass
     public static void setUpClass() throws Exception {
-        HdtDataSourceType.register();
+        final String typeName = "HdtTestSourceType";
+        if ( ! DataSourceTypesRegistry.isRegistered(typeName) ) {
+            DataSourceTypesRegistry.register( typeName, new HdtDataSourceType() );
+        }
+
         // HDT does not seem to support an InputReader, so write to temp file
         File temp = getResourceAsFile();
 
@@ -37,8 +42,7 @@ public static void setUpClass() throws Exception {
         temp.getAbsoluteFile().delete();
 
         // Everything is in place, now create the LDF datasource
-        JsonObject config = createConfig("hdt test", "hdt test", 
-                HdtDataSourceType.TYPE_NAME);
+        JsonObject config = createConfig("hdt test", "hdt test", typeName);
 
         JsonObject settings = new JsonObject();
         settings.addProperty("file", hdtfile.getAbsolutePath());

src/test/java/org/linkeddatafragments/datasource/JenaTDBDataSourceTest.java

@@ -19,6 +19,7 @@
 import org.junit.BeforeClass;
 
 import org.linkeddatafragments.datasource.DataSourceFactory;
+import org.linkeddatafragments.datasource.DataSourceTypesRegistry;
 import org.linkeddatafragments.datasource.tdb.JenaTDBDataSourceType;
 
 /**
@@ -31,7 +32,11 @@ public class JenaTDBDataSourceTest extends DataSourceTest {
 
     @BeforeClass
     public static void setUpClass() throws Exception {
-        JenaTDBDataSourceType.register();
+        final String typeName = "JenaSourceType";
+        if ( ! DataSourceTypesRegistry.isRegistered(typeName) ) {
+            DataSourceTypesRegistry.register( typeName,
+                                              new JenaTDBDataSourceType() );
+        }
 
         String tmpdir = System.getProperty("java.io.tmpdir");
         jena = new File(tmpdir, "ldf-jena-test");
@@ -46,7 +51,7 @@ public static void setUpClass() throws Exception {
 
         // Everything is in place, now create the LDF datasource                
         JsonObject config = createConfig("jena tdb test", "jena tdb test",
-                                                    JenaTDBDataSourceType.TYPE_NAME);
+                                         typeName);
 
         JsonObject settings = new JsonObject();
         settings.addProperty("directory", jena.getAbsolutePath());