- fixes a bug where the content type of a post request would be forcibly overridden

src/main/java/com/microsoft/graph/http/CoreHttpProvider.java

@@ -260,7 +260,9 @@ public <Result, Body> Request getHttpRequest(final IHttpRequest request,
 			// This ensures that the Content-Length header is properly set
 			if (request.getHttpMethod() == HttpMethod.POST) {
 				bytesToWrite = new byte[0];
-				contenttype = Constants.BINARY_CONTENT_TYPE;
+				if(contenttype == null) {
+					contenttype = Constants.BINARY_CONTENT_TYPE;
+				}
 			}
 			else {
 				bytesToWrite = null;

src/test/java/com/microsoft/graph/functional/UserTests.java

@@ -1,21 +1,28 @@
 package com.microsoft.graph.functional;
 
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.InputStream;
+import java.util.ArrayList;
 import java.util.List;
 
 import org.junit.Before;
 import org.junit.Ignore;
 import org.junit.Test;
 
+import okhttp3.Request;
+
+import com.microsoft.graph.http.HttpMethod;
 import com.microsoft.graph.models.extensions.Drive;
 import com.microsoft.graph.models.extensions.DriveItem;
 import com.microsoft.graph.models.extensions.IGraphServiceClient;
 import com.microsoft.graph.models.extensions.ProfilePhoto;
 import com.microsoft.graph.models.extensions.User;
+import com.microsoft.graph.options.HeaderOption;
+import com.microsoft.graph.options.Option;
 import com.microsoft.graph.requests.extensions.IContactCollectionPage;
 import com.microsoft.graph.requests.extensions.IDirectoryObjectCollectionWithReferencesPage;
 import com.microsoft.graph.requests.extensions.IDriveItemCollectionPage;
@@ -164,4 +171,18 @@ public void meMemberof() {
 		assertNotNull(page);
 	}
 
+	@Test
+	public void emptyPostContentType() {
+		final String contentTypeValue = "application/json";
+		final HeaderOption ctype = new HeaderOption("Content-Type", contentTypeValue);
+        final ArrayList<Option> options = new ArrayList<>();
+        options.add(ctype);
+        final Request request = graphServiceClient.me()
+                                            .revokeSignInSessions()
+                                            .buildRequest(options)
+                                            .withHttpMethod(HttpMethod.POST)
+                                            .getHttpRequest();
+		assertEquals(contentTypeValue, request.body().contentType().toString());					
+	}
+
 }