diff --git a/apps/emqx_authn/src/emqx_authn_api.erl b/apps/emqx_authn/src/emqx_authn_api.erl
index bef27f99d..36c1e9b6c 100644
--- a/apps/emqx_authn/src/emqx_authn_api.erl
+++ b/apps/emqx_authn/src/emqx_authn_api.erl
@@ -896,7 +896,7 @@ serialize_error({bad_ssl_config, Details}) ->
             message => binfmt("bad_ssl_config ~p", [Details])}};
 serialize_error({missing_parameter, Detail}) ->
     {400, #{code => <<"MISSING_PARAMETER">>,
-            message => binfmt("Missing required parameter", [Detail])}};
+            message => binfmt("Missing required parameter: ~p", [Detail])}};
 serialize_error({invalid_parameter, Name}) ->
     {400, #{code => <<"INVALID_PARAMETER">>,
             message => binfmt("Invalid value for '~p'", [Name])}};
diff --git a/apps/emqx_authn/test/emqx_authn_api_SUITE.erl b/apps/emqx_authn/test/emqx_authn_api_SUITE.erl
index 654aa042a..bcbd39a16 100644
--- a/apps/emqx_authn/test/emqx_authn_api_SUITE.erl
+++ b/apps/emqx_authn/test/emqx_authn_api_SUITE.erl
@@ -136,12 +136,10 @@ test_authenticators(PathPrefix) ->
 
 test_authenticator(PathPrefix) ->
     ValidConfig0 = emqx_authn_test_lib:http_example(),
-
     {ok, 200, _} = request(
                      post,
                      uri(PathPrefix ++ ["authentication"]),
                      ValidConfig0),
-
     {ok, 200, _} = request(
                      get,
                      uri(PathPrefix ++ ["authentication", "password-based:http"])),
@@ -262,9 +260,7 @@ test_authenticator_user(PathPrefix) ->
       fun(UserUpdate) -> {ok, 200, _} = request(put, UsersUri ++ "/u1", UserUpdate) end,
       ValidUserUpdates),
 
-    InvalidUserUpdates = [
-                          #{user_id => <<"u1">>, password => <<"p1">>},
-                          #{is_superuser => true}],
+    InvalidUserUpdates = [#{user_id => <<"u1">>, password => <<"p1">>}],
 
     lists:foreach(
       fun(UserUpdate) -> {ok, 400, _} = request(put, UsersUri ++ "/u1", UserUpdate) end,
diff --git a/apps/emqx_bridge/test/emqx_bridge_api_SUITE.erl b/apps/emqx_bridge/test/emqx_bridge_api_SUITE.erl
index e898d0dc4..af3ae1c07 100644
--- a/apps/emqx_bridge/test/emqx_bridge_api_SUITE.erl
+++ b/apps/emqx_bridge/test/emqx_bridge_api_SUITE.erl
@@ -56,7 +56,7 @@ init_per_suite(Config) ->
             port => 18083
         }]
     }),
-    ok = application:load(emqx_conf),
+    _ = application:load(emqx_conf),
     ok = emqx_common_test_helpers:start_apps([emqx_bridge, emqx_dashboard]),
     ok = emqx_config:init_load(emqx_bridge_schema, ?CONF_DEFAULT),
     Config.
diff --git a/apps/emqx_connector/src/emqx_connector_http.erl b/apps/emqx_connector/src/emqx_connector_http.erl
index 5bfd72b6b..23fed81dd 100644
--- a/apps/emqx_connector/src/emqx_connector_http.erl
+++ b/apps/emqx_connector/src/emqx_connector_http.erl
@@ -101,6 +101,7 @@ For example: http://localhost:9901/
     , {request, hoconsc:mk(
         ref("request"),
         #{ default => undefined
+         , nullable => true
          , desc => """
 If the request is provided, the caller can send HTTP requests via
 <code>emqx_resource:query(ResourceId, {send_message, BridgeId, Message})</code>
@@ -109,13 +110,13 @@ If the request is provided, the caller can send HTTP requests via
     ] ++ emqx_connector_schema_lib:ssl_fields();
 
 fields("request") ->
-    [ {method, hoconsc:mk(hoconsc:enum([post, put, get, delete]), #{})}
-    , {path, hoconsc:mk(binary(), #{})}
-    , {body, hoconsc:mk(binary(), #{})}
-    , {headers, hoconsc:mk(map(), #{})}
+    [ {method, hoconsc:mk(hoconsc:enum([post, put, get, delete]), #{nullable => true})}
+    , {path, hoconsc:mk(binary(), #{nullable => true})}
+    , {body, hoconsc:mk(binary(), #{nullable => true})}
+    , {headers, hoconsc:mk(map(), #{nullable => true})}
     , {request_timeout,
         sc(emqx_schema:duration_ms(),
-           #{ default => "30s"
+           #{ nullable => true
             , desc => "The timeout when sending request to the HTTP server"
             })}
     ].
@@ -222,20 +223,22 @@ on_health_check(_InstId, #{host := Host, port := Port} = State) ->
 %%--------------------------------------------------------------------
 %% Internal functions
 %%--------------------------------------------------------------------
+
 preprocess_request(undefined) ->
     undefined;
+preprocess_request(Req) when map_size(Req) == 0 ->
+    undefined;
 preprocess_request(#{
             method := Method,
             path := Path,
             body := Body,
-            headers := Headers,
-            request_timeout := ReqTimeout
-        }) ->
+            headers := Headers
+        } = Req) ->
     #{ method => emqx_plugin_libs_rule:preproc_tmpl(bin(Method))
      , path => emqx_plugin_libs_rule:preproc_tmpl(Path)
      , body => emqx_plugin_libs_rule:preproc_tmpl(Body)
      , headers => preproc_headers(Headers)
-     , request_timeout => ReqTimeout
+     , request_timeout => maps:get(request_timeout, Req, 30000)
      }.
 
 preproc_headers(Headers) ->
diff --git a/apps/emqx_connector/test/emqx_connector_api_SUITE.erl b/apps/emqx_connector/test/emqx_connector_api_SUITE.erl
index c9bd58394..e82d0bf7d 100644
--- a/apps/emqx_connector/test/emqx_connector_api_SUITE.erl
+++ b/apps/emqx_connector/test/emqx_connector_api_SUITE.erl
@@ -67,7 +67,7 @@ init_per_suite(Config) ->
             port => 18083
         }]
     }),
-    ok = application:load(emqx_conf),
+    _ = application:load(emqx_conf),
     ok = emqx_common_test_helpers:start_apps([emqx_connector, emqx_bridge, emqx_dashboard]),
     ok = emqx_config:init_load(emqx_connector_schema, ?CONF_DEFAULT),
     ok = emqx_config:init_load(emqx_bridge_schema, ?BRIDGE_CONF_DEFAULT),
@@ -76,6 +76,7 @@ init_per_suite(Config) ->
 end_per_suite(_Config) ->
     ok = ekka:stop(),
     emqx_common_test_helpers:stop_apps([emqx_connector, emqx_bridge, emqx_dashboard]),
+    application:unload(emqx_conf),
     ok.
 
 init_per_testcase(_, Config) ->
diff --git a/apps/emqx_dashboard/src/emqx_dashboard_swagger.erl b/apps/emqx_dashboard/src/emqx_dashboard_swagger.erl
index 89ceb6254..b6724f701 100644
--- a/apps/emqx_dashboard/src/emqx_dashboard_swagger.erl
+++ b/apps/emqx_dashboard/src/emqx_dashboard_swagger.erl
@@ -200,7 +200,7 @@ check_request_body(#{body := Body}, Schema, Module, CheckFun, true) ->
             _ -> Type0
         end,
     NewSchema = ?INIT_SCHEMA#{roots => [{root, Type}]},
-    Option = #{override_env => false},
+    Option = #{override_env => false, nullable => true},
     #{<<"root">> := NewBody} = CheckFun(NewSchema, #{<<"root">> => Body}, Option),
     NewBody;
 %% TODO not support nest object check yet, please use ref!