Improve ContentResolver for DeGruyter

src/main/java/org/gesis/dda/publishing/domain/impl/ContentResolver.java

@@ -319,10 +319,13 @@ public class ContentResolver {
         if ( seedUrlString.contains("wbv.de") || seedUrlString.contains("budrich-academic.de") ) {
             result = new UseNthPdfOnPageStrategy(0);
         }
-        else if ( seedUrlString.contains("journals.sub.uni-hamburg.de") ) {
+        else if ( seedUrlString.contains("journals.sub.uni-hamburg.de") || seedUrlString.contains("degruyter.com") ) {
             // unfortunately, SUB Uni Hamburg's OJS instances report an incorrect HTML citation_pdf_url
             // meta element which points not to the actual PDF bitstream, but the landing page.
             // Therefore, we discard all possible (X)HTML bitstream heuristics
+            
+            // DeGruyter provides in all known cases single chapter PDFs, not full PDFs. Therefore we discard
+            // results from degruyter.com and rely on alternative PDF sources
             result = new EmptySetResolvingStrategy();
         }
         else {

src/test/java/org/gesis/dda/publishing/domain/impl/ContentResolverTest.java

@@ -690,6 +690,17 @@ public class ContentResolverTest {
         assertTrue(isEqual);
     }
     
+    
+    @Test
+    public void resolveDeGruyterDoi() throws MalformedURLException, IOException {
+        String underTest = "https://doi.org/10.14361/9783839437124";
+        Metadatum metadatum = new SimpleMetadatum("dc.identifier.doi", underTest);
+        Set<Metadatum> metadata = ImmutableSet.of(metadatum);
+        
+        Set<InputStreamAndFilenameSupplier> suppliers = ContentResolver.resolveContentsSuppliers(metadata);
+        assertEquals(0, suppliers.size());
+    }
+    
     public static String unrootDomainName(String url) {
         try {
             String result;