Fix issue with zip files being disallowed with fileServer (#501)

* Add test for downloading zip files using fileServer

* Use default test name (test index)

* Add partial content test for zip files

* Allow zip files to be downloaded with fileServer

* Fix test expected length

tds/src/integrationTests/java/thredds/server/fileserver/TestFileServer.java

@@ -67,6 +67,11 @@ public static List<Object[]> getTestParameters() {
     result.add(new Object[] {"fileServer/scanCdmUnitTests/formats/netcdf3/files/ctest0.nc",
         ContentType.netcdf.toString(), "4b514d280c034222e8e5b8401fee268c"});
 
+    result
+        .add(new Object[] {"fileServer/scanLocal/oneFile.zip", "application/zip", "088e88fe16b8cd4ac73b5ef540393439"});
+    result
+        .add(new Object[] {"fileServer/scanLocal/twoFiles.zip", "application/zip", "a9d6538c628654e2840de4afa5d85aad"});
+
     return result;
   }
 

tds/src/integrationTests/java/thredds/server/fileserver/TestPartialContent.java

@@ -18,7 +18,7 @@
 public class TestPartialContent {
   private static final Logger logger = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());
 
-  @Parameterized.Parameters(name = "{0}")
+  @Parameterized.Parameters
   static public List<long[]> getTestParameters() {
     final List<long[]> result = new ArrayList<>();
 
@@ -38,13 +38,25 @@ public void shouldReturnPartialContent() {
     final String path = "fileServer/scanLocal/mydata1.nc";
     final long maxSize = 66832;
     final String contentType = ContentType.netcdf.toString();
+    checkPartialContent(path, maxSize, contentType);
+  }
+
+  @Test
+  public void shouldReturnPartialContentOfZip() {
+    final String path = "fileServer/scanLocal/twoFiles.zip";
+    final long maxSize = 667;
+    final String contentType = "application/zip";
+    checkPartialContent(path, maxSize, contentType);
+  }
+
+  private void checkPartialContent(String path, long maxSize, String contentType) {
     final String endpoint = TestOnLocalServer.withHttpPath(path);
 
     final byte[] content = TestOnLocalServer.getContent(null, endpoint,
         new int[] {HttpServletResponse.SC_PARTIAL_CONTENT}, contentType, byteRange);
     assertThat(content).isNotNull();
 
-    final long expectedLength = Math.min(byteRange[1] - byteRange[0] + 1, maxSize);
+    final long expectedLength = Math.min(byteRange[1] - byteRange[0] + 1, maxSize - byteRange[0]);
     assertThat(content.length).isEqualTo(expectedLength);
   }
 }

tds/src/main/java/thredds/servlet/ServletUtil.java

@@ -295,7 +295,7 @@ public static void writeMFileToResponse(HttpServletRequest request, HttpServletR
       return;
     }
 
-    if (file.isDirectory()) {
+    if (file.isDirectory() && !file.isZipFile()) {
       response.sendError(HttpServletResponse.SC_BAD_REQUEST,
           "Expected a file name instead of a directory for URL path: " + requestPath);
       return;