fix: fix download for empty files (#1231)

Author: mwwoda

src/intTest/java/com/box/sdk/BoxFileIT.java

@@ -966,6 +966,36 @@ public void setsAndRetrievesDispositionAt() throws ParseException {
         }
     }
 
+    @Test
+    public void uploadAndDownloadEmptyFileSucceeds() throws IOException {
+        BoxAPIConnection api = jwtApiForServiceAccount();
+        BoxFolder folder = getUniqueFolder(api);
+        String fileName = "empty_file";
+        URL fileURL = this.getClass().getResource("/sample-files/" + fileName);
+        String filePath = URLDecoder.decode(fileURL.getFile(), "utf-8");
+        long fileSize = new File(filePath).length();
+        byte[] fileContent = readAllBytes(filePath);
+        BoxFile uploadedFile = null;
+        try {
+            InputStream uploadStream = Files.newInputStream(Paths.get(filePath));
+            ProgressListener mockUploadListener = mock(ProgressListener.class);
+            BoxFile.Info uploadedFileInfo = folder.uploadFile(
+                uploadStream, BoxFileIT.generateString(), fileSize, mockUploadListener
+            );
+            uploadedFile = uploadedFileInfo.getResource();
+
+            ByteArrayOutputStream downloadStream = new ByteArrayOutputStream();
+            uploadedFile.download(downloadStream);
+            byte[] downloadedFileContent = downloadStream.toByteArray();
+
+            assertThat(downloadedFileContent, is(equalTo(fileContent)));
+            assertThat(folder, hasItem(Matchers.<BoxItem.Info>hasProperty("ID", equalTo(uploadedFile.getID()))));
+        } finally {
+            deleteFile(uploadedFile);
+        }
+
+    }
+
     private byte[] readFileContent(String fileName) throws IOException {
         URL fileURL = this.getClass().getResource("/sample-files/" + fileName);
         String filePath = URLDecoder.decode(fileURL.getFile(), "utf-8");

src/main/java/com/box/sdk/BoxAPIResponse.java

@@ -148,19 +148,18 @@ static BoxAPIResponse toBoxResponse(Response response) {
             );
         }
         ResponseBody responseBody = response.body();
-        if (responseBody.contentLength() == 0 || responseBody.contentType() == null) {
+        if (responseBody.contentType() == null) {
             try {
-                return new BoxAPIResponse(response.code(),
-                        response.request().method(),
-                        response.request().url().toString(),
-                        response.headers().toMultimap()
-                );
+                return emptyContentResponse(response);
             } finally {
                 responseBody.close();
             }
         }
         if (responseBody != null && responseBody.contentType() != null) {
             if (responseBody.contentType().toString().contains(APPLICATION_JSON)) {
+                if (responseBody.contentLength() == 0) {
+                    return emptyContentResponse(response);
+                }
                 String bodyAsString = "";
                 try {
                     bodyAsString = responseBody.string();
@@ -189,6 +188,14 @@ static BoxAPIResponse toBoxResponse(Response response) {
         );
     }
 
+    private static BoxAPIResponse emptyContentResponse(Response response) {
+        return new BoxAPIResponse(response.code(),
+            response.request().method(),
+            response.request().url().toString(),
+            response.headers().toMultimap()
+        );
+    }
+
     /**
      * Gets the response code returned by the API.
      *