Ensure workbooks are closed after reading/writing

main/src/com/google/refine/exporters/XlsExporter.java

@@ -141,8 +141,8 @@ public class XlsExporter implements StreamExporter {
                 project, engine, params, serializer);
         
         wb.write(outputStream);
-        wb.close();
         outputStream.flush();
+        wb.close();
     }
 
 }

main/src/com/google/refine/importers/ExcelImporter.java

@@ -117,6 +117,7 @@ public class ExcelImporter extends TabularImportingParserBase {
                                 }
                                 JSONUtilities.append(sheetRecords, sheetRecord);
                             }
+                            wb.close();
                 } finally {
                     is.close();
                 }
@@ -146,7 +147,6 @@ public class ExcelImporter extends TabularImportingParserBase {
         Workbook wb = null;
         if (!inputStream.markSupported()) {
           inputStream = new BufferedInputStream(inputStream);
-;
         }
         
         try {

main/tests/server/src/com/google/refine/tests/importers/ExcelImporterTests.java

@@ -222,6 +222,7 @@ public class ExcelImporterTests extends ImporterTest {
             wb.write(outputStream);
             outputStream.flush();
             outputStream.close();
+            wb.close();
         } catch (IOException e) {
             return null;
         }