Always add Content-Length header

gax-httpjson/src/main/java/com/google/api/gax/httpjson/HttpJsonStatusCode.java

@@ -80,6 +80,10 @@ static StatusCode.Code httpStatusToStatusCode(int httpStatus, String errorMessag
         } else {
           return Code.ABORTED;
         }
+      case 411:
+        throw new IllegalStateException(
+            "411 status code received (Content-Length header not given.) Please file a bug against https://github.com/googleapis/gax-java/\n"
+                + httpStatus);
       case 429:
         return Code.RESOURCE_EXHAUSTED;
       case 499:

gax-httpjson/src/main/java/com/google/api/gax/httpjson/HttpRequestRunnable.java

@@ -29,7 +29,9 @@
  */
 package com.google.api.gax.httpjson;
 
+import com.google.api.client.http.EmptyContent;
 import com.google.api.client.http.GenericUrl;
+import com.google.api.client.http.HttpContent;
 import com.google.api.client.http.HttpMediaType;
 import com.google.api.client.http.HttpRequest;
 import com.google.api.client.http.HttpRequestFactory;
@@ -88,12 +90,16 @@ HttpRequest createHttpRequest() throws IOException {
 
     // Create HTTP request body.
     String requestBody = requestFormatter.getRequestBody(getRequest());
-    JsonHttpContent jsonHttpContent = null;
+    HttpContent jsonHttpContent;
     if (!Strings.isNullOrEmpty(requestBody)) {
       getJsonFactory().createJsonParser(requestBody).parse(tokenRequest);
       jsonHttpContent =
           new JsonHttpContent(getJsonFactory(), tokenRequest)
               .setMediaType((new HttpMediaType("application/json")));
+    } else {
+      // Force underlying HTTP lib to set Content-Length header to avoid 411s.
+      // See EmptyContent.java.
+      jsonHttpContent = new EmptyContent();
     }
 
     // Populate URL path and query parameters.

gax-httpjson/src/test/java/com/google/api/gax/httpjson/HttpRequestRunnableTest.java

@@ -29,6 +29,7 @@
  */
 package com.google.api.gax.httpjson;
 
+import com.google.api.client.http.EmptyContent;
 import com.google.api.client.http.HttpRequest;
 import com.google.api.client.json.jackson2.JacksonFactory;
 import com.google.api.client.testing.http.MockHttpTransport;
@@ -161,6 +162,7 @@ public String serialize(Void response) {
   @Test
   public void testRequestUrl() throws IOException {
     HttpRequest httpRequest = httpRequestRunnable.createHttpRequest();
+    Truth.assertThat(httpRequest.getContent()).isInstanceOf(EmptyContent.class);
     String expectedUrl = ENDPOINT + "name/feline" + "?food=bird&food=mouse&size=small";
     Truth.assertThat(httpRequest.getUrl().toString()).isEqualTo(expectedUrl);
   }