diff --git a/apps/emqx_rule_engine/src/emqx_rule_actions.erl b/apps/emqx_rule_engine/src/emqx_rule_actions.erl
index edeffbde4..ae82d56c9 100644
--- a/apps/emqx_rule_engine/src/emqx_rule_actions.erl
+++ b/apps/emqx_rule_engine/src/emqx_rule_actions.erl
@@ -35,24 +35,47 @@
             },
             target_qos => #{
                 order => 2,
-                type => number,
-                enum => [-1, 0, 1, 2],
+                input => editable_select,
+                type => [number, string],
+                enum => [0, 1, 2, <<"${qos}">>],
                 required => true,
                 default => 0,
                 title => #{en => <<"Target QoS">>,
                            zh => <<"目的 QoS"/utf8>>},
-                description => #{en => <<"The QoS Level to be uses when republishing the message. Set to -1 to use the original QoS">>,
-                                 zh => <<"重新发布消息时用的 QoS 级别, 设置为 -1 以使用原消息中的 QoS"/utf8>>}
+                description => #{en =>
+                                    <<"The QoS Level to be used when republishing the message."
+                                      " Support placeholder variables."
+                                      " Set to ${qos} to use the original QoS. Default is 0">>,
+                                 zh =>
+                                    <<"重新发布消息时用的 QoS 级别。"
+                                      "支持占位符变量，可以填写 ${qos} 来使用原消息的 QoS。默认 0"/utf8>>}
+            },
+            target_retain => #{
+                order => 3,
+                input => editable_select,
+                type => [boolean, string],
+                enum => [true, false, <<"${flags.retain}">>],
+                required => false,
+                default => false,
+                title => #{en => <<"Target Retain">>,
+                           zh => <<"目标保留消息标识"/utf8>>},
+                description => #{en => <<"The Retain flag to be used when republishing the message."
+                                         " Set to ${flags.retain} to use the original Retain."
+                                         " Support placeholder variables. Default is false">>,
+                                 zh => <<"重新发布消息时用的保留消息标识。"
+                                         "支持占位符变量，可以填写 ${flags.retain} 来使用原消息的 Retain。"
+                                         "默认 false"/utf8>>}
             },
             payload_tmpl => #{
-                order => 3,
+                order => 4,
                 type => string,
                 input => textarea,
                 required => false,
                 default => <<"${payload}">>,
                 title => #{en => <<"Payload Template">>,
                            zh => <<"消息内容模板"/utf8>>},
-                description => #{en => <<"The payload template, variable interpolation is supported">>,
+                description => #{en => <<"The payload template, "
+                                         "variable interpolation is supported">>,
                                  zh => <<"消息内容模板，支持变量"/utf8>>}
             }
         }).
@@ -89,7 +112,8 @@
                params => #{},
                title => #{en => <<"Do Nothing (debug)">>,
                           zh => <<"空动作 (调试)"/utf8>>},
-               description => #{en => <<"This action does nothing and never fails. It's for debug purpose">>,
+               description => #{en => <<"This action does nothing and never fails. "
+                                        "It's for debug purpose">>,
                                 zh => <<"此动作什么都不做，并且不会失败 (用以调试)"/utf8>>}
               }).
 
@@ -113,7 +137,8 @@ on_resource_create(_Name, Conf) ->
 %%------------------------------------------------------------------------------
 %% Action 'inspect'
 %%------------------------------------------------------------------------------
--spec on_action_create_inspect(Id :: action_instance_id(), Params :: map()) -> {bindings(), NewParams :: map()}.
+-spec on_action_create_inspect(Id :: action_instance_id(), Params :: map()) ->
+    {bindings(), NewParams :: map()}.
 on_action_create_inspect(Id, Params) ->
     Params.
 
@@ -129,12 +154,15 @@ on_action_inspect(Selected, Envs) ->
 %%------------------------------------------------------------------------------
 %% Action 'republish'
 %%------------------------------------------------------------------------------
--spec on_action_create_republish(action_instance_id(), Params :: map()) -> {bindings(), NewParams :: map()}.
+-spec on_action_create_republish(action_instance_id(), Params :: map()) ->
+    {bindings(), NewParams :: map()}.
 on_action_create_republish(Id, Params = #{
         <<"target_topic">> := TargetTopic,
-        <<"target_qos">> := TargetQoS,
+        <<"target_qos">> := TargetQoS0,
         <<"payload_tmpl">> := PayloadTmpl
        }) ->
+    TargetRetain = to_retain(maps:get(<<"target_retain">>, Params, <<"false">>)),
+    TargetQoS = to_qos(TargetQoS0),
     TopicTks = emqx_rule_utils:preproc_tmpl(TargetTopic),
     PayloadTks = emqx_rule_utils:preproc_tmpl(PayloadTmpl),
     Params.
@@ -157,20 +185,21 @@ on_action_republish(Selected, _Envs = #{
                 'TargetQoS' := TargetQoS,
                 'TopicTks' := TopicTks,
                 'PayloadTks' := PayloadTks
-            }}) ->
-    ?LOG(debug, "[republish] republish to: ~p, Payload: ~p",
-        [TargetTopic, Selected]),
-    increase_and_publish(ActId,
+            } = Bindings}) ->
+    ?LOG(debug, "[republish] republish to: ~p, Selected: ~p", [TargetTopic, Selected]),
+    TargetRetain = maps:get('TargetRetain', Bindings, false),
+    Message =
         #message{
             id = emqx_guid:gen(),
-            qos = if TargetQoS =:= -1 -> QoS; true -> TargetQoS end,
+            qos = get_qos(TargetQoS, Selected, QoS),
             from = ActId,
-            flags = Flags,
+            flags = Flags#{retain => get_retain(TargetRetain, Selected)},
             headers = #{republish_by => ActId},
             topic = emqx_rule_utils:proc_tmpl(TopicTks, Selected),
             payload = format_msg(PayloadTks, Selected),
             timestamp = Timestamp
-        });
+        },
+    increase_and_publish(ActId, Message);
 
 %% in case this is not a "message.publish" request
 on_action_republish(Selected, _Envs = #{
@@ -180,27 +209,29 @@ on_action_republish(Selected, _Envs = #{
                 'TargetQoS' := TargetQoS,
                 'TopicTks' := TopicTks,
                 'PayloadTks' := PayloadTks
-            }}) ->
-    ?LOG(debug, "[republish] republish to: ~p, Payload: ~p",
-        [TargetTopic, Selected]),
-    increase_and_publish(ActId,
+            } = Bindings}) ->
+    ?LOG(debug, "[republish] republish to: ~p, Selected: ~p", [TargetTopic, Selected]),
+    TargetRetain = maps:get('TargetRetain', Bindings, false),
+    Message =
         #message{
             id = emqx_guid:gen(),
-            qos = if TargetQoS =:= -1 -> 0; true -> TargetQoS end,
+            qos = get_qos(TargetQoS, Selected, 0),
             from = ActId,
-            flags = #{dup => false, retain => false},
+            flags = #{dup => false, retain => get_retain(TargetRetain, Selected)},
             headers = #{republish_by => ActId},
             topic = emqx_rule_utils:proc_tmpl(TopicTks, Selected),
             payload = format_msg(PayloadTks, Selected),
             timestamp = erlang:system_time(millisecond)
-        }).
+        },
+    increase_and_publish(ActId, Message).
 
 increase_and_publish(ActId, Msg) ->
     _ = emqx_broker:safe_publish(Msg),
     emqx_rule_metrics:inc_actions_success(ActId),
     emqx_metrics:inc_msg(Msg).
 
--spec on_action_create_do_nothing(action_instance_id(), Params :: map()) -> {bindings(), NewParams :: map()}.
+-spec on_action_create_do_nothing(action_instance_id(), Params :: map()) ->
+    {bindings(), NewParams :: map()}.
 on_action_create_do_nothing(ActId, Params) when is_binary(ActId) ->
     Params.
 
@@ -211,3 +242,57 @@ format_msg([], Data) ->
     emqx_json:encode(Data);
 format_msg(Tokens, Data) ->
      emqx_rule_utils:proc_tmpl(Tokens, Data).
+
+%% -1 for old version.
+to_qos(<<"-1">>) -> -1;
+to_qos(-1) -> -1;
+to_qos(TargetQoS) ->
+    try
+        qos(TargetQoS)
+    catch _:_ ->
+        %% Use placeholder.
+        case emqx_rule_utils:preproc_tmpl(TargetQoS) of
+            Tmpl = [{var, _}] ->
+                Tmpl;
+            _BadQoS ->
+                error({bad_qos, TargetQoS})
+        end
+    end.
+
+get_qos(-1, _Data, Default) -> Default;
+get_qos(TargetQoS, Data, _Default) ->
+    qos(emqx_rule_utils:replace_var(TargetQoS, Data)).
+
+qos(<<"0">>) ->  0;
+qos(<<"1">>) ->  1;
+qos(<<"2">>) ->  2;
+qos(0) ->        0;
+qos(1) ->        1;
+qos(2) ->        2;
+qos(BadQoS) -> error({bad_qos, BadQoS}).
+
+to_retain(TargetRetain) ->
+    try
+        retain(TargetRetain)
+    catch _:_ ->
+        %% Use placeholder.
+        case emqx_rule_utils:preproc_tmpl(TargetRetain) of
+            Tmpl = [{var, _}] ->
+                Tmpl;
+            _BadRetain ->
+                error({bad_retain, TargetRetain})
+        end
+    end.
+
+get_retain(TargetRetain, Data) ->
+    retain(emqx_rule_utils:replace_var(TargetRetain, Data)).
+
+retain(true) ->        true;
+retain(false) ->       false;
+retain(<<"true">>) ->  true;
+retain(<<"false">>) -> false;
+retain(<<"1">>) ->     true;
+retain(<<"0">>) ->     false;
+retain(1) ->           true;
+retain(0) ->           false;
+retain(BadRetain) -> error({bad_retain, BadRetain}).
diff --git a/apps/emqx_rule_engine/src/emqx_rule_engine.appup.src b/apps/emqx_rule_engine/src/emqx_rule_engine.appup.src
index 7b4049254..b92d67e4f 100644
--- a/apps/emqx_rule_engine/src/emqx_rule_engine.appup.src
+++ b/apps/emqx_rule_engine/src/emqx_rule_engine.appup.src
@@ -1,9 +1,15 @@
 %% -*- mode: erlang -*-
 %% Unless you know what you are doing, DO NOT edit manually!!
 {VSN,
-  [{"4.3.10",[{load_module,emqx_rule_registry,brutal_purge,soft_purge,[]}]},
+  [{"4.3.10",
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_utils,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_actions,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_registry,brutal_purge,soft_purge,[]}]},
    {"4.3.9",
-    [{load_module,emqx_rule_utils,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_actions,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_utils,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_events,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_funcs,brutal_purge,soft_purge,[]},
      {add_module,emqx_rule_date},
@@ -12,7 +18,9 @@
      {load_module,emqx_rule_engine,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_api,brutal_purge,soft_purge,[]}]},
    {"4.3.8",
-    [{load_module,emqx_rule_utils,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_actions,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_utils,brutal_purge,soft_purge,[]},
      {add_module,emqx_rule_date},
      {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_cli,brutal_purge,soft_purge,[]},
@@ -25,7 +33,9 @@
      {load_module,emqx_rule_registry,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_funcs,brutal_purge,soft_purge,[]}]},
    {"4.3.7",
-    [{add_module,emqx_rule_date},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_actions,brutal_purge,soft_purge,[]},
+     {add_module,emqx_rule_date},
      {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_cli,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_sqltester,brutal_purge,soft_purge,[]},
@@ -38,7 +48,9 @@
      {load_module,emqx_rule_utils,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_registry,brutal_purge,soft_purge,[]}]},
    {"4.3.6",
-    [{add_module,emqx_rule_date},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_actions,brutal_purge,soft_purge,[]},
+     {add_module,emqx_rule_date},
      {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_cli,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_sqltester,brutal_purge,soft_purge,[]},
@@ -51,7 +63,9 @@
      {load_module,emqx_rule_runtime,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_api,brutal_purge,soft_purge,[]}]},
    {"4.3.5",
-    [{add_module,emqx_rule_date},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_actions,brutal_purge,soft_purge,[]},
+     {add_module,emqx_rule_date},
      {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_cli,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_sqltester,brutal_purge,soft_purge,[]},
@@ -64,7 +78,9 @@
      {load_module,emqx_rule_engine,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_api,brutal_purge,soft_purge,[]}]},
    {"4.3.4",
-    [{add_module,emqx_rule_date},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_actions,brutal_purge,soft_purge,[]},
+     {add_module,emqx_rule_date},
      {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_cli,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_sqltester,brutal_purge,soft_purge,[]},
@@ -77,7 +93,8 @@
      {load_module,emqx_rule_engine,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_api,brutal_purge,soft_purge,[]}]},
    {"4.3.3",
-    [{add_module,emqx_rule_date},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {add_module,emqx_rule_date},
      {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_cli,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_sqltester,brutal_purge,soft_purge,[]},
@@ -91,7 +108,8 @@
      {load_module,emqx_rule_runtime,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_api,brutal_purge,soft_purge,[]}]},
    {"4.3.2",
-    [{add_module,emqx_rule_date},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {add_module,emqx_rule_date},
      {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_cli,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_sqltester,brutal_purge,soft_purge,[]},
@@ -106,7 +124,8 @@
      {load_module,emqx_rule_runtime,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_api,brutal_purge,soft_purge,[]}]},
    {"4.3.1",
-    [{add_module,emqx_rule_date},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {add_module,emqx_rule_date},
      {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_cli,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_sqltester,brutal_purge,soft_purge,[]},
@@ -121,7 +140,8 @@
      {load_module,emqx_rule_runtime,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_api,brutal_purge,soft_purge,[]}]},
    {"4.3.0",
-    [{add_module,emqx_rule_date},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {add_module,emqx_rule_date},
      {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_cli,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_sqltester,brutal_purge,soft_purge,[]},
@@ -136,9 +156,15 @@
      {load_module,emqx_rule_runtime,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_api,brutal_purge,soft_purge,[]}]},
    {<<".*">>,[]}],
-  [{"4.3.10",[{load_module,emqx_rule_registry,brutal_purge,soft_purge,[]}]},
+  [{"4.3.10",
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_utils,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_actions,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_registry,brutal_purge,soft_purge,[]}]},
    {"4.3.9",
-    [{load_module,emqx_rule_utils,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_actions,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_utils,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_events,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_funcs,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
@@ -147,7 +173,9 @@
      {load_module,emqx_rule_engine_api,brutal_purge,soft_purge,[]},
      {delete_module,emqx_rule_date}]},
    {"4.3.8",
-    [{load_module,emqx_rule_utils,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_actions,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_utils,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_cli,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_sqltester,brutal_purge,soft_purge,[]},
@@ -160,7 +188,9 @@
      {load_module,emqx_rule_funcs,brutal_purge,soft_purge,[]},
      {delete_module,emqx_rule_date}]},
    {"4.3.7",
-    [{load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_actions,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_cli,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_sqltester,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_runtime,brutal_purge,soft_purge,[]},
@@ -173,7 +203,9 @@
      {load_module,emqx_rule_registry,brutal_purge,soft_purge,[]},
      {delete_module,emqx_rule_date}]},
    {"4.3.6",
-    [{load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_actions,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_cli,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_sqltester,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_funcs,brutal_purge,soft_purge,[]},
@@ -186,7 +218,9 @@
      {load_module,emqx_rule_engine_api,brutal_purge,soft_purge,[]},
      {delete_module,emqx_rule_date}]},
    {"4.3.5",
-    [{load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_actions,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_cli,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_sqltester,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_funcs,brutal_purge,soft_purge,[]},
@@ -199,7 +233,9 @@
      {load_module,emqx_rule_engine_api,brutal_purge,soft_purge,[]},
      {delete_module,emqx_rule_date}]},
    {"4.3.4",
-    [{load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_actions,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_cli,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_sqltester,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_funcs,brutal_purge,soft_purge,[]},
@@ -212,7 +248,8 @@
      {load_module,emqx_rule_engine_api,brutal_purge,soft_purge,[]},
      {delete_module,emqx_rule_date}]},
    {"4.3.3",
-    [{load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_cli,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_sqltester,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_funcs,brutal_purge,soft_purge,[]},
@@ -226,7 +263,8 @@
      {load_module,emqx_rule_engine_api,brutal_purge,soft_purge,[]},
      {delete_module,emqx_rule_date}]},
    {"4.3.2",
-    [{load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_cli,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_sqltester,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_funcs,brutal_purge,soft_purge,[]},
@@ -241,7 +279,8 @@
      {load_module,emqx_rule_engine_api,brutal_purge,soft_purge,[]},
      {delete_module,emqx_rule_date}]},
    {"4.3.1",
-    [{load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_cli,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_sqltester,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_funcs,brutal_purge,soft_purge,[]},
@@ -256,7 +295,8 @@
      {load_module,emqx_rule_engine_api,brutal_purge,soft_purge,[]},
      {delete_module,emqx_rule_date}]},
    {"4.3.0",
-    [{load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_rule_validator,brutal_purge,soft_purge,[]},
+     {load_module,emqx_rule_maps,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_engine_cli,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_sqltester,brutal_purge,soft_purge,[]},
      {load_module,emqx_rule_utils,brutal_purge,soft_purge,[]},
diff --git a/apps/emqx_rule_engine/src/emqx_rule_utils.erl b/apps/emqx_rule_engine/src/emqx_rule_utils.erl
index d287f1ad0..137e22128 100644
--- a/apps/emqx_rule_engine/src/emqx_rule_utils.erl
+++ b/apps/emqx_rule_engine/src/emqx_rule_utils.erl
@@ -16,6 +16,9 @@
 
 -module(emqx_rule_utils).
 
+-export([ replace_var/2
+        ]).
+
 %% preprocess and process tempalte string with place holders
 -export([ preproc_tmpl/1
         , proc_tmpl/2
@@ -87,6 +90,14 @@ preproc_tmpl([[Str, Phld]| Tokens], Acc) ->
 preproc_tmpl([[Str]| Tokens], Acc) ->
     preproc_tmpl(Tokens, put_head(str, Str, Acc)).
 
+%% Replace a simple var to its value. For example, given "${var}", if the var=1, then the result
+%% value will be an integer 1.
+replace_var(Tokens, Data) when is_list(Tokens) ->
+    [Val] = proc_tmpl(Tokens, Data, #{return => rawlist}),
+    Val;
+replace_var(Val, _Data) ->
+    Val.
+
 put_head(_Type, <<>>, List) -> List;
 put_head(Type, Term, List) ->
     [{Type, Term} | List].
diff --git a/apps/emqx_rule_engine/src/emqx_rule_validator.erl b/apps/emqx_rule_engine/src/emqx_rule_validator.erl
index e32ec66ab..237e5dfba 100644
--- a/apps/emqx_rule_engine/src/emqx_rule_validator.erl
+++ b/apps/emqx_rule_engine/src/emqx_rule_validator.erl
@@ -84,6 +84,8 @@ validate_spec(ParamsSepc) ->
 %% Internal Functions
 %%------------------------------------------------------------------------------
 
+validate_value(Val, #{type := Types} = Spec) when is_list(Types) ->
+    validate_types(Val, Types, Spec);
 validate_value(Val, #{enum := Enum}) ->
     validate_enum(Val, Enum);
 validate_value(Val, #{type := object} = Spec) ->
@@ -91,6 +93,15 @@ validate_value(Val, #{type := object} = Spec) ->
 validate_value(Val, #{type := Type} = Spec) ->
     validate_type(Val, Type, Spec).
 
+validate_types(Val, [], _Spec) ->
+    throw({invalid_data_type, Val});
+validate_types(Val, [Type | Types], Spec) ->
+    try
+        validate_type(Val, Type, Spec)
+    catch _:_ ->
+        validate_types(Val, Types, Spec)
+    end.
+
 validate_type(Val, file, _Spec) ->
     validate_file(Val);
 validate_type(Val, String, Spec) when String =:= string;
@@ -157,6 +168,9 @@ do_validate_spec(Name, #{type := array} = Spec) ->
         fun (not_found) -> throw({required_field_missing, {items, {in, Name}}});
             (Items) -> do_validate_spec(Name, Items)
         end);
+do_validate_spec(_Name, #{type := Types}) when is_list(Types) ->
+    _ = [ok = supported_data_type(Type, ?DATA_TYPES) || Type <- Types],
+    ok;
 do_validate_spec(_Name, #{type := Type}) ->
     _ = supported_data_type(Type, ?DATA_TYPES);
 
diff --git a/apps/emqx_rule_engine/test/emqx_rule_engine_SUITE.erl b/apps/emqx_rule_engine/test/emqx_rule_engine_SUITE.erl
index 6263c8440..663eddd5a 100644
--- a/apps/emqx_rule_engine/test/emqx_rule_engine_SUITE.erl
+++ b/apps/emqx_rule_engine/test/emqx_rule_engine_SUITE.erl
@@ -405,15 +405,31 @@ t_reset_metrics(_Config) ->
     ok.
 
 t_republish_action(_Config) ->
-    Qos0Received = emqx_metrics:val('messages.qos0.received'),
+    TargetQoSList = [-1, 0, 1, 2, <<"${qos}">>],
+    TargetRetainList = [true, false, <<"${flags.retain}">>],
+    [[republish_action_test(TargetQoS, TargetRetain) || TargetRetain <- TargetRetainList]
+        || TargetQoS <- TargetQoSList],
+    ok.
+
+republish_action_test(TargetQoS, TargetRetain) ->
+    {QoSReceivedMetricsName, PubQoS} =
+        case TargetQoS of
+            <<"${qos}">> -> {'messages.qos0.received', 0};
+            -1 -> {'messages.qos0.received', 0};
+            0 -> {'messages.qos0.received', 0};
+            1 -> {'messages.qos1.received', 1};
+            2 -> {'messages.qos2.received', 2}
+        end,
+    QosReceived = emqx_metrics:val(QoSReceivedMetricsName),
     Received = emqx_metrics:val('messages.received'),
     ok = emqx_rule_engine:load_providers(),
     {ok, #rule{id = Id, for = [<<"t1">>]}} =
         emqx_rule_engine:create_rule(
-                    #{rawsql => <<"select topic, payload, qos from \"t1\"">>,
+                    #{rawsql => <<"select * from \"t1\"">>,
                       actions => [#{name => 'republish',
                                     args => #{<<"target_topic">> => <<"t2">>,
-                                              <<"target_qos">> => -1,
+                                              <<"target_qos">> => TargetQoS,
+                                              <<"target_retain">> => TargetRetain,
                                               <<"payload_tmpl">> => <<"${payload}">>}}],
                       description => <<"builtin-republish-rule">>}),
     {ok, Client} = emqtt:start_link([{username, <<"emqx">>}]),
@@ -421,7 +437,7 @@ t_republish_action(_Config) ->
     {ok, _, _} = emqtt:subscribe(Client, <<"t2">>, 0),
 
     Msg = <<"{\"id\": 1, \"name\": \"ha\"}">>,
-    emqtt:publish(Client, <<"t1">>, Msg, 0),
+    emqtt:publish(Client, <<"t1">>, Msg, PubQoS),
     receive {publish, #{topic := <<"t2">>, payload := Payload}} ->
         ?assertEqual(Msg, Payload)
     after 1000 ->
@@ -429,7 +445,7 @@ t_republish_action(_Config) ->
     end,
     emqtt:stop(Client),
     emqx_rule_registry:remove_rule(Id),
-    ?assertEqual(2, emqx_metrics:val('messages.qos0.received') - Qos0Received),
+    ?assertEqual(2, emqx_metrics:val(QoSReceivedMetricsName) - QosReceived),
     ?assertEqual(2, emqx_metrics:val('messages.received') - Received),
     ok.
 
@@ -479,7 +495,7 @@ t_crud_rule_api(_Config) ->
                         {<<"params">>,[
                             {<<"arg1">>,1},
                             {<<"target_topic">>, <<"t2">>},
-                            {<<"target_qos">>, -1},
+                            {<<"target_qos">>, 0},
                             {<<"payload_tmpl">>, <<"${payload}">>}
                         ]}
                     ]]