Set empty body on POST instead of null

Fixes a bug where POST requests with no bodies do not set a Content-Length header.
Added a functional test to verify behavior of sending POST with no body.

Also removed an unused String constant

Author: Caitlin Bales (MSFT)

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

@@ -212,7 +212,6 @@ private <Result, Body, DeserializeType> Result sendRequestInternal(final IHttpRe
                                                                        final IStatefulResponseHandler<Result, DeserializeType> handler)
             throws ClientException {
         final int defaultBufferSize = 4096;
-        final String contentLengthHeaderName = "Content-Length";
         final String binaryContentType = "application/octet-stream";
 
         try {
@@ -234,7 +233,14 @@ private <Result, Body, DeserializeType> Result sendRequestInternal(final IHttpRe
                 final byte[] bytesToWrite;
                 connection.addRequestHeader("Accept", "*/*");
                 if (serializable == null) {
-                    bytesToWrite = null;
+                	// Send an empty body through with a POST request
+                	// This ensures that the Content-Length header is properly set
+                	if (request.getHttpMethod() == HttpMethod.POST) {
+                		bytesToWrite = new byte[0];
+                	}
+                	else {
+                		bytesToWrite = null;
+                	}
                 } else if (serializable instanceof byte[]) {
                     logger.logDebug("Sending byte[] as request body");
                     bytesToWrite = (byte[]) serializable;

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

@@ -4,6 +4,8 @@
 import com.microsoft.graph.models.extensions.Message;
 import com.microsoft.graph.models.extensions.Recipient;
 import com.microsoft.graph.models.extensions.User;
+import com.microsoft.graph.options.QueryOption;
+import com.microsoft.graph.requests.extensions.IMessageCollectionPage;
 import com.microsoft.graph.requests.extensions.IUserCollectionPage;
 
 import org.junit.Test;
@@ -18,7 +20,6 @@
 
 import javax.xml.datatype.DatatypeFactory;
 import javax.xml.datatype.Duration;
-import java.lang.reflect.Array;
 
 import java.util.ArrayList;
 
@@ -72,4 +73,36 @@ public void testGetFindMeetingTimes() {
         }
 
     }
+    
+    @Test
+    public void testSendDraft() {
+    	TestBase testBase = new TestBase();
+    	
+    	//Attempt to identify the sent message via randomly generated subject
+    	String draftSubject = "Draft Test Message " + Double.toString(Math.random()*1000);
+    	
+        User me = testBase.graphClient.me().buildRequest().get();
+        Recipient r = new Recipient();
+        EmailAddress address = new EmailAddress();
+        address.address = me.mail;
+        r.emailAddress = address;
+        Message message = new Message();
+        message.subject = draftSubject;
+        ArrayList<Recipient> recipients = new ArrayList<Recipient>();
+        recipients.add(r);
+        message.toRecipients = recipients;
+        message.isDraft = true;
+        
+        //Save the message as a draft
+        Message newMessage = testBase.graphClient.me().messages().buildRequest().post(message);
+    	//Send the drafted message
+    	testBase.graphClient.me().mailFolders("Drafts").messages(newMessage.id).send().buildRequest().post();
+    	
+    	java.util.List<QueryOption> options = new ArrayList<QueryOption>();
+    	QueryOption o = new QueryOption("$filter", "subject eq '" + draftSubject + "'");
+    	options.add(o);
+    	//Check that the sent message exists on the server
+    	IMessageCollectionPage mcp = testBase.graphClient.me().messages().buildRequest(options).get();
+    	assertFalse(mcp.getCurrentPage().isEmpty());
+    }
 }