GRDDL filters loaded susing ServiceLoader

Author: namedgraph

src/main/java/com/atomgraph/linkeddatahub/Application.java

@@ -70,7 +70,8 @@
 import com.atomgraph.client.util.XsltResolver;
 import com.atomgraph.linkeddatahub.client.GraphStoreClient;
 import com.atomgraph.linkeddatahub.client.filter.ClientUriRewriteFilter;
-import com.atomgraph.linkeddatahub.client.filter.grddl.YouTubeGRDDLFilter;
+import com.atomgraph.linkeddatahub.client.filter.JSONGRDDLFilter;
+import com.atomgraph.linkeddatahub.client.filter.JSONGRDDLFilterProvider;
 import com.atomgraph.linkeddatahub.imports.ImportExecutor;
 import com.atomgraph.linkeddatahub.io.HtmlJsonLDReaderFactory;
 import com.atomgraph.linkeddatahub.io.JsonLDReader;
@@ -153,6 +154,7 @@
 import java.security.cert.CertificateException;
 import java.security.cert.X509Certificate;
 import java.util.HashMap;
+import java.util.ServiceLoader;
 import java.util.Map;
 import java.util.Properties;
 import jakarta.mail.Authenticator;
@@ -1168,17 +1170,19 @@ protected void registerExceptionMappers()
      */
     protected void registerClientFilters()
     {
-        try
-        {
-            // Register YouTube GRDDL filter
-            YouTubeGRDDLFilter youtubeFilter = new YouTubeGRDDLFilter(xsltComp);
-            client.register(youtubeFilter);
-            externalClient.register(youtubeFilter);
-        }
-        catch (SaxonApiException ex)
+        ServiceLoader.load(JSONGRDDLFilterProvider.class).forEach(provider ->
         {
-            if (log.isErrorEnabled()) log.error("Failed to initialize GRDDL client filter");
-        }
+            try
+            {
+                JSONGRDDLFilter filter = provider.getFilter(xsltComp);
+                client.register(filter);
+                externalClient.register(filter);
+            }
+            catch (SaxonApiException ex)
+            {
+                if (log.isErrorEnabled()) log.error("Failed to initialize GRDDL client filter for {}", provider.getClass().getSimpleName());
+            }
+        });
     }
 
     /**

src/main/java/com/atomgraph/linkeddatahub/client/filter/JSONGRDDLFilterProvider.java

@@ -0,0 +1,31 @@
+/**
+ *  Copyright 2025 Martynas Jusevičius <martynas@atomgraph.com>
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ */
+package com.atomgraph.linkeddatahub.client.filter;
+
+import net.sf.saxon.s9api.SaxonApiException;
+import net.sf.saxon.s9api.XsltCompiler;
+
+/**
+ * SPI interface for providing {@link JSONGRDDLFilter} instances.
+ * Implementations are discovered via {@link java.util.ServiceLoader}.
+ */
+public interface JSONGRDDLFilterProvider
+{
+
+    JSONGRDDLFilter getFilter(XsltCompiler xsltCompiler) throws SaxonApiException;
+
+}

src/main/java/com/atomgraph/linkeddatahub/client/filter/grddl/YouTubeGRDDLFilterProvider.java

@@ -0,0 +1,36 @@
+/**
+ *  Copyright 2025 Martynas Jusevičius <martynas@atomgraph.com>
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ */
+package com.atomgraph.linkeddatahub.client.filter.grddl;
+
+import com.atomgraph.linkeddatahub.client.filter.JSONGRDDLFilter;
+import com.atomgraph.linkeddatahub.client.filter.JSONGRDDLFilterProvider;
+import net.sf.saxon.s9api.SaxonApiException;
+import net.sf.saxon.s9api.XsltCompiler;
+
+/**
+ * {@link JSONGRDDLFilterProvider} implementation for YouTube GRDDL transformation.
+ */
+public class YouTubeGRDDLFilterProvider implements JSONGRDDLFilterProvider
+{
+
+    @Override
+    public JSONGRDDLFilter getFilter(XsltCompiler xsltCompiler) throws SaxonApiException
+    {
+        return new YouTubeGRDDLFilter(xsltCompiler);
+    }
+
+}

src/main/resources/META-INF/services/com.atomgraph.linkeddatahub.client.filter.JSONGRDDLFilterProvider

@@ -0,0 +1 @@
+com.atomgraph.linkeddatahub.client.filter.grddl.YouTubeGRDDLFilterProvider