Add Wikibase schema exporter, for issue #1776

extensions/wikidata/src/org/openrefine/wikidata/exporters/SchemaExporter.java

@@ -0,0 +1,31 @@
+package org.openrefine.wikidata.exporters;
+
+import java.io.IOException;
+import java.io.Writer;
+import java.util.Properties;
+
+import org.json.JSONWriter;
+import org.openrefine.wikidata.schema.WikibaseSchema;
+
+import com.google.refine.browsing.Engine;
+import com.google.refine.exporters.WriterExporter;
+import com.google.refine.model.Project;
+
+public class SchemaExporter implements WriterExporter {
+
+	@Override
+	public String getContentType() {
+		return "application/octet-stream";
+	}
+
+	@Override
+	public void export(Project project, Properties options, Engine engine, Writer writer) throws IOException {
+        WikibaseSchema schema = (WikibaseSchema) project.overlayModels.get("wikibaseSchema");
+        if (schema == null) {
+            schema = new WikibaseSchema();
+        }
+        JSONWriter jsonWriter = new JSONWriter(writer);
+        schema.write(jsonWriter, new Properties());
+	}
+
+}

extensions/wikidata/tests/src/org/openrefine/wikidata/exporters/SchemaExporterTest.java

@@ -0,0 +1,30 @@
+package org.openrefine.wikidata.exporters;
+
+import static org.openrefine.wikidata.testing.JacksonSerializationTest.assertJsonEquals;
+
+import java.io.IOException;
+import java.io.StringWriter;
+import java.util.Properties;
+
+import org.testng.annotations.Test;
+
+import com.google.refine.browsing.Engine;
+import com.google.refine.model.Project;
+import com.google.refine.tests.RefineTest;
+
+public class SchemaExporterTest extends RefineTest {
+	
+	private SchemaExporter exporter = new SchemaExporter();
+	
+    @Test
+    public void testNoSchema()
+            throws IOException {
+        Project project = this.createCSVProject("a,b\nc,d");
+        Engine engine = new Engine(project);
+        StringWriter writer = new StringWriter();
+        Properties properties = new Properties();
+        exporter.export(project, properties, engine, writer);
+        assertJsonEquals("{\"itemDocuments\":[]}", writer.toString());
+    }
+
+}