set content-length header for DefaultFullHttpResponse (#1779)

core/src/main/java/com/taobao/arthas/core/shell/term/impl/http/HttpRequestHandler.java

@@ -112,8 +112,7 @@ public class HttpRequestHandler extends SimpleChannelInboundHandler<FullHttpRequ
                     response = createResponse(request, HttpResponseStatus.INTERNAL_SERVER_ERROR, "Server error");
                 }
                 if (!isFileResponseFinished) {
-                    ctx.write(response);
-                    ChannelFuture future = ctx.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT);
+                    ChannelFuture future = writeResponse(ctx, response);
                     future.addListener(ChannelFutureListener.CLOSE);
                     //reuse http api response buf
                     if (isHttpApiResponse && response instanceof DefaultFullHttpResponse) {
@@ -130,6 +129,20 @@ public class HttpRequestHandler extends SimpleChannelInboundHandler<FullHttpRequ
         }
     }
 
+    private ChannelFuture writeResponse(ChannelHandlerContext ctx, HttpResponse response) {
+        // try to add content-length header for DefaultFullHttpResponse
+        if (!HttpUtil.isTransferEncodingChunked(response)
+            && response instanceof DefaultFullHttpResponse) {
+            response.headers().set(HttpHeaderNames.CONTENT_LENGTH,
+                ((DefaultFullHttpResponse) response).content().readableBytes());
+            return ctx.writeAndFlush(response);
+        }
+
+        //chunk response
+        ctx.write(response);
+        return ctx.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT);
+    }
+
     private HttpResponse readFileFromResource(FullHttpRequest request, String path) throws IOException {
         DefaultFullHttpResponse fullResp = null;
         InputStream in = null;