Refactor of DOI import failure dialog, import format reader and clipboard manager

src/main/java/org/jabref/gui/mergeentries/FetchAndMergeEntry.java

@@ -16,6 +16,8 @@
 import org.jabref.gui.undo.UndoableFieldChange;
 import org.jabref.gui.util.BackgroundTask;
 import org.jabref.gui.util.TaskExecutor;
+import org.jabref.logic.importer.DOIDataNotFoundException;
+import org.jabref.logic.importer.DOIServerNotAvailableException;
 import org.jabref.logic.importer.EntryBasedFetcher;
 import org.jabref.logic.importer.IdBasedFetcher;
 import org.jabref.logic.importer.ImportCleanup;
@@ -76,7 +78,16 @@ public void fetchAndMerge(BibEntry entry, List<Field> fields) {
                                   })
                                   .onFailure(exception -> {
                                       LOGGER.error("Error while fetching bibliographic information", exception);
-                                      dialogService.showErrorDialogAndWait(exception);
+                                      // client error
+                                      if (exception instanceof DOIDataNotFoundException) {
+                                          dialogService.showInformationDialogAndWait(Localization.lang("Lookup DOI"), Localization.lang("No DOI data was found"));
+                                      // server error
+                                      } else if (exception instanceof DOIServerNotAvailableException) {
+                                          dialogService.showInformationDialogAndWait(Localization.lang("Lookup DOI"), Localization.lang("DOI server not available"));
+                                      // default error
+                                      } else {
+                                          dialogService.showErrorDialogAndWait(exception);
+                                      }
                                   })
                                   .executeWith(Globals.TASK_EXECUTOR);
                 }

src/main/java/org/jabref/logic/importer/DOIDataNotFoundException.java

@@ -0,0 +1,16 @@
+package org.jabref.logic.importer;
+
+public class DOIDataNotFoundException extends FetcherException {
+
+    public DOIDataNotFoundException(String errorMessage, Throwable cause) {
+        super(errorMessage, cause);
+    }
+
+    public DOIDataNotFoundException(String errorMessage) {
+        super(errorMessage);
+    }
+
+    public DOIDataNotFoundException(String errorMessage, String localizedMessage, Throwable cause) {
+        super(errorMessage, localizedMessage, cause);
+    }
+}

src/main/java/org/jabref/logic/importer/DOIServerNotAvailableException.java

@@ -0,0 +1,15 @@
+package org.jabref.logic.importer;
+
+public class DOIServerNotAvailableException extends FetcherException {
+    public DOIServerNotAvailableException(String errorMessage, Throwable cause) {
+        super(errorMessage, cause);
+    }
+
+    public DOIServerNotAvailableException(String errorMessage) {
+        super(errorMessage);
+    }
+
+    public DOIServerNotAvailableException(String errorMessage, String localizedMessage, Throwable cause) {
+        super(errorMessage, localizedMessage, cause);
+    }
+}

src/main/java/org/jabref/logic/importer/fetcher/DoiFetcher.java

@@ -1,5 +1,6 @@
 package org.jabref.logic.importer.fetcher;
 
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.net.URL;
 import java.util.Collections;
@@ -11,6 +12,8 @@
 import org.jabref.logic.formatter.bibtexfields.ClearFormatter;
 import org.jabref.logic.formatter.bibtexfields.NormalizePagesFormatter;
 import org.jabref.logic.help.HelpFile;
+import org.jabref.logic.importer.DOIDataNotFoundException;
+import org.jabref.logic.importer.DOIServerNotAvailableException;
 import org.jabref.logic.importer.EntryBasedFetcher;
 import org.jabref.logic.importer.FetcherException;
 import org.jabref.logic.importer.IdBasedFetcher;
@@ -72,7 +75,6 @@ public Optional<BibEntry> performSearchById(String identifier) throws FetcherExc
                     return new Medra().performSearchById(identifier);
                 }
                 URL doiURL = new URL(doi.get().getURIAsASCIIString());
-
                 // BibTeX data
                 URLDownload download = getUrlDownload(doiURL);
                 download.addHeader("Accept", MediaTypes.APPLICATION_BIBTEX);
@@ -81,7 +83,12 @@ public Optional<BibEntry> performSearchById(String identifier) throws FetcherExc
                     bibtexString = download.asString();
                 } catch (IOException e) {
                     // an IOException will be thrown if download is unable to download from the doiURL
-                    throw new FetcherException(Localization.lang("No DOI data exists"), e);
+                    // dispatch the IOException
+                    if (e instanceof FileNotFoundException) {
+                        throw new DOIDataNotFoundException(Localization.lang("Client Error"), e);
+                    } else {
+                        throw new DOIServerNotAvailableException(Localization.lang("Server Error"), e);
+                    }
                 }
 
                 // BibTeX entry

src/main/resources/l10n/JabRef_en.properties

@@ -580,8 +580,6 @@ No\ journal\ names\ could\ be\ abbreviated.=No journal names could be abbreviate
 
 No\ journal\ names\ could\ be\ unabbreviated.=No journal names could be unabbreviated.
 
-No\ DOI\ data\ exists=No DOI data exists
-
 not=not
 
 not\ found=not found
@@ -2487,3 +2485,9 @@ Success\!\ Finished\ writing\ metadata.=Success! Finished writing metadata.
 
 Custom\ API\ key=Custom API key
 Check\ %0\ API\ Key\ Setting=Check %0 API Key Setting
+
+Client\ Error=Client Error
+DOI\ server\ not\ available=DOI server not available
+Lookup\ DOI=Lookup DOI
+No\ DOI\ data\ was\ found=No DOI data was found
+Server\ Error=Server Error

src/test/java/org/jabref/logic/importer/fetcher/DoiFetcherTest.java

@@ -2,6 +2,7 @@
 
 import java.util.Optional;
 
+import org.jabref.logic.importer.DOIDataNotFoundException;
 import org.jabref.logic.importer.FetcherException;
 import org.jabref.logic.importer.ImportFormatPreferences;
 import org.jabref.model.entry.BibEntry;
@@ -117,6 +118,18 @@ public void testPerformSearchInvalidDOI() {
         assertThrows(FetcherException.class, () -> fetcher.performSearchById("10.1002/9781118257517F"));
     }
 
+    // test invalid DOI client error message "Client Error"
+    @Test
+    public void testPerformSearchInvalidDOIClientErrorMessage1() {
+        assertThrows(DOIDataNotFoundException.class, () -> fetcher.performSearchById("10.1002/9781118257517F"));
+    }
+
+    // test invalid DOI client error message "Client Error"
+    @Test
+    public void testPerformSearchInvalidDOIClientErrorMessage2() {
+        assertThrows(DOIDataNotFoundException.class, () -> fetcher.performSearchById("10.1002/9781517F"));
+    }
+
     @Test
     public void testPerformSearchNonTrimmedDOI() throws FetcherException {
         Optional<BibEntry> fetchedEntry = fetcher.performSearchById("http s://doi.org/ 10.1109 /ICWS .2007.59 ");