diff --git a/apps/emqx_exhook/priv/protos/exhook.proto b/apps/emqx_exhook/priv/protos/exhook.proto
index 8dc9641b9..41f471d14 100644
--- a/apps/emqx_exhook/priv/protos/exhook.proto
+++ b/apps/emqx_exhook/priv/protos/exhook.proto
@@ -16,6 +16,12 @@
 
 syntax = "proto3";
 
+option csharp_namespace = "Emqx.Exhook.V1";
+option go_package = "emqx.io/grpc/exhook";
+option java_multiple_files = true;
+option java_package = "io.emqx.exhook";
+option java_outer_classname = "EmqxExHookProto";
+
 package emqx.exhook.v1;
 
 service HookProvider {
diff --git a/apps/emqx_exhook/src/emqx_exhook_handler.erl b/apps/emqx_exhook/src/emqx_exhook_handler.erl
index 980fb7786..b93f23cdd 100644
--- a/apps/emqx_exhook/src/emqx_exhook_handler.erl
+++ b/apps/emqx_exhook/src/emqx_exhook_handler.erl
@@ -307,26 +307,11 @@ stringfy(Term) when is_atom(Term) ->
 stringfy(Term) ->
     unicode:characters_to_binary((io_lib:format("~0p", [Term]))).
 
-hexstr(<<>>) -> [];
-hexstr(<<H:4, L:4, B/binary>>) ->
-    iolist_to_binary([hexchar(H), hexchar(L)] ++ hexstr(B)).
+hexstr(B) ->
+    << <<(hexchar(H)), (hexchar(L))>> || <<H:4, L:4>> <= B>>.
 
-hexchar(0) -> $0;
-hexchar(1) -> $1;
-hexchar(2) -> $2;
-hexchar(3) -> $3;
-hexchar(4) -> $4;
-hexchar(5) -> $5;
-hexchar(6) -> $6;
-hexchar(7) -> $7;
-hexchar(8) -> $8;
-hexchar(9) -> $9;
-hexchar(10) -> $A;
-hexchar(11) -> $B;
-hexchar(12) -> $C;
-hexchar(13) -> $D;
-hexchar(14) -> $E;
-hexchar(15) -> $F.
+hexchar(I) when I >= 0 andalso I < 10 -> I + $0;
+hexchar(I) -> I - 10 + $A.
 
 %%--------------------------------------------------------------------
 %% Acc funcs