Set default CONTENT_TYPE when it is absent in multipart request body

Motivation:

I am use netty as a http server, it fail to decode some POST request when the request absent Content-Type in the multipart/form-data body.

Modifications:

Set content_type with default application/octet-stream to parse the uploaded file data when the Content-Type is absent in multipart request body

Result:

Can decode the http request as normal.

codec-http/src/main/java/io/netty/handler/codec/http/multipart/HttpPostMultipartRequestDecoder.java

@@ -863,9 +863,6 @@ public class HttpPostMultipartRequestDecoder implements InterfaceHttpPostRequest
             Attribute filenameAttribute = currentFieldAttributes.get(HttpHeaderValues.FILENAME);
             Attribute nameAttribute = currentFieldAttributes.get(HttpHeaderValues.NAME);
             Attribute contentTypeAttribute = currentFieldAttributes.get(HttpHeaderNames.CONTENT_TYPE);
-            if (contentTypeAttribute == null) {
-                throw new ErrorDataDecoderException("Content-Type is absent but required");
-            }
             Attribute lengthAttribute = currentFieldAttributes.get(HttpHeaderNames.CONTENT_LENGTH);
             long size;
             try {
@@ -876,9 +873,15 @@ public class HttpPostMultipartRequestDecoder implements InterfaceHttpPostRequest
                 size = 0;
             }
             try {
+                String contentType;
+                if (contentTypeAttribute != null) {
+                    contentType = contentTypeAttribute.getValue();
+                } else {
+                    contentType = HttpPostBodyUtil.DEFAULT_BINARY_CONTENT_TYPE;
+                }
                 currentFileUpload = factory.createFileUpload(request,
                         cleanString(nameAttribute.getValue()), cleanString(filenameAttribute.getValue()),
-                        contentTypeAttribute.getValue(), mechanism.value(), localCharset,
+                        contentType, mechanism.value(), localCharset,
                         size);
             } catch (NullPointerException e) {
                 throw new ErrorDataDecoderException(e);

codec-http/src/test/java/io/netty/handler/codec/http/multipart/HttpPostRequestDecoderTest.java

@@ -379,4 +379,34 @@ public class HttpPostRequestDecoderTest {
         assertEquals("tmp 0.txt", fileUpload.getFilename());
         decoder.destroy();
     }
+
+    @Test
+    public void testMultipartRequestWithoutContentTypeBody() {
+        final String boundary = "dLV9Wyq26L_-JQxk6ferf-RT153LhOO";
+
+        final DefaultFullHttpRequest req = new DefaultFullHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.POST,
+                "http://localhost");
+
+        req.setDecoderResult(DecoderResult.SUCCESS);
+        req.headers().add(HttpHeaderNames.CONTENT_TYPE, "multipart/form-data; boundary=" + boundary);
+        req.headers().add(HttpHeaderNames.TRANSFER_ENCODING, HttpHeaderValues.CHUNKED);
+
+        // Force to use memory-based data.
+        final DefaultHttpDataFactory inMemoryFactory = new DefaultHttpDataFactory(false);
+
+        for (String data : Arrays.asList("", "\r", "\r\r", "\r\r\r")) {
+            final String body =
+                    "--" + boundary + "\r\n" +
+                            "Content-Disposition: form-data; name=\"file\"; filename=\"tmp-0.txt\"\r\n" +
+                            "\r\n" +
+                            data + "\r\n" +
+                            "--" + boundary + "--\r\n";
+
+            req.content().writeBytes(body.getBytes(CharsetUtil.UTF_8));
+        }
+        // Create decoder instance to test without any exception.
+        final HttpPostRequestDecoder decoder = new HttpPostRequestDecoder(inMemoryFactory, req);
+        assertFalse(decoder.getBodyHttpDatas().isEmpty());
+        decoder.destroy();
+    }
 }