diff --git a/superset/charts/commands/export.py b/superset/charts/commands/export.py
index 405a679fde..88a87d9015 100644
--- a/superset/charts/commands/export.py
+++ b/superset/charts/commands/export.py
@@ -57,7 +57,7 @@ class ExportChartsCommand(ExportModelsCommand):
         # becomes the default export endpoint
         for key in REMOVE_KEYS:
             del payload[key]
-        if "params" in payload:
+        if payload.get("params"):
             try:
                 payload["params"] = json.loads(payload["params"])
             except json.decoder.JSONDecodeError:
diff --git a/superset/dashboards/commands/export.py b/superset/dashboards/commands/export.py
index 8f103d73c3..9a1af4721f 100644
--- a/superset/dashboards/commands/export.py
+++ b/superset/dashboards/commands/export.py
@@ -108,7 +108,7 @@ class ExportDashboardsCommand(ExportModelsCommand):
         # TODO (betodealmeida): move this logic to export_to_dict once this
         # becomes the default export endpoint
         for key, new_name in JSON_KEYS.items():
-            if key in payload:
+            if payload.get(key):
                 value = payload.pop(key)
                 try:
                     payload[new_name] = json.loads(value)
diff --git a/superset/dashboards/commands/importers/v1/utils.py b/superset/dashboards/commands/importers/v1/utils.py
index de3e4e84a6..5052080957 100644
--- a/superset/dashboards/commands/importers/v1/utils.py
+++ b/superset/dashboards/commands/importers/v1/utils.py
@@ -109,8 +109,8 @@ def import_dashboard(
             value = config.pop(key)
             try:
                 config[new_name] = json.dumps(value)
-            except json.decoder.JSONDecodeError:
-                logger.info("Unable to decode `%s` field: %s", key, value)
+            except TypeError:
+                logger.info("Unable to encode `%s` field: %s", key, value)
 
     dashboard = Dashboard.import_from_dict(session, config, recursive=False)
     if dashboard.id is None:
diff --git a/superset/databases/commands/export.py b/superset/databases/commands/export.py
index e8937867d1..f373ce101a 100644
--- a/superset/databases/commands/export.py
+++ b/superset/databases/commands/export.py
@@ -50,7 +50,7 @@ class ExportDatabasesCommand(ExportModelsCommand):
         )
         # TODO (betodealmeida): move this logic to export_to_dict once this
         # becomes the default export endpoint
-        if "extra" in payload:
+        if payload.get("extra"):
             try:
                 payload["extra"] = json.loads(payload["extra"])
             except json.decoder.JSONDecodeError:
diff --git a/superset/datasets/commands/export.py b/superset/datasets/commands/export.py
index e86b932295..64946f48f2 100644
--- a/superset/datasets/commands/export.py
+++ b/superset/datasets/commands/export.py
@@ -31,6 +31,8 @@ from superset.utils.dict_import_export import EXPORT_VERSION
 
 logger = logging.getLogger(__name__)
 
+JSON_KEYS = {"params", "template_params", "extra"}
+
 
 class ExportDatasetsCommand(ExportModelsCommand):
 
@@ -49,6 +51,20 @@ class ExportDatasetsCommand(ExportModelsCommand):
             include_defaults=True,
             export_uuids=True,
         )
+        # TODO (betodealmeida): move this logic to export_to_dict once this
+        # becomes the default export endpoint
+        for key in JSON_KEYS:
+            if payload.get(key):
+                try:
+                    payload[key] = json.loads(payload[key])
+                except json.decoder.JSONDecodeError:
+                    logger.info("Unable to decode `%s` field: %s", key, payload[key])
+        for metric in payload.get("metrics", []):
+            if metric.get("extra"):
+                try:
+                    metric["extra"] = json.loads(metric["extra"])
+                except json.decoder.JSONDecodeError:
+                    logger.info("Unable to decode `extra` field: %s", metric["extra"])
 
         payload["version"] = EXPORT_VERSION
         payload["database_uuid"] = str(model.database.uuid)
@@ -67,7 +83,7 @@ class ExportDatasetsCommand(ExportModelsCommand):
         )
         # TODO (betodealmeida): move this logic to export_to_dict once this
         # becomes the default export endpoint
-        if "extra" in payload:
+        if payload.get("extra"):
             try:
                 payload["extra"] = json.loads(payload["extra"])
             except json.decoder.JSONDecodeError:
diff --git a/superset/datasets/commands/importers/v1/utils.py b/superset/datasets/commands/importers/v1/utils.py
index 99326f3c3d..1857e05245 100644
--- a/superset/datasets/commands/importers/v1/utils.py
+++ b/superset/datasets/commands/importers/v1/utils.py
@@ -15,12 +15,18 @@
 # specific language governing permissions and limitations
 # under the License.
 
+import json
+import logging
 from typing import Any, Dict
 
 from sqlalchemy.orm import Session
 
 from superset.connectors.sqla.models import SqlaTable
 
+logger = logging.getLogger(__name__)
+
+JSON_KEYS = {"params", "template_params", "extra"}
+
 
 def import_dataset(
     session: Session, config: Dict[str, Any], overwrite: bool = False
@@ -31,6 +37,21 @@ def import_dataset(
             return existing
         config["id"] = existing.id
 
+    # TODO (betodealmeida): move this logic to import_from_dict
+    config = config.copy()
+    for key in JSON_KEYS:
+        if config.get(key):
+            try:
+                config[key] = json.dumps(config[key])
+            except TypeError:
+                logger.info("Unable to encode `%s` field: %s", key, config[key])
+    for metric in config.get("metrics", []):
+        if metric.get("extra"):
+            try:
+                metric["extra"] = json.dumps(metric["extra"])
+            except TypeError:
+                logger.info("Unable to encode `extra` field: %s", metric["extra"])
+
     # should we delete columns and metrics not present in the current import?
     sync = ["columns", "metrics"] if overwrite else []
 
diff --git a/superset/datasets/schemas.py b/superset/datasets/schemas.py
index 2703228739..4cbb2e05f4 100644
--- a/superset/datasets/schemas.py
+++ b/superset/datasets/schemas.py
@@ -145,7 +145,7 @@ class ImportV1MetricSchema(Schema):
     expression = fields.String(required=True)
     description = fields.String(allow_none=True)
     d3format = fields.String(allow_none=True)
-    extra = fields.String(allow_none=True)
+    extra = fields.Dict(allow_none=True)
     warning_text = fields.String(allow_none=True)
 
 
@@ -158,11 +158,11 @@ class ImportV1DatasetSchema(Schema):
     cache_timeout = fields.Integer(allow_none=True)
     schema = fields.String(allow_none=True)
     sql = fields.String(allow_none=True)
-    params = fields.String(allow_none=True)
-    template_params = fields.String(allow_none=True)
+    params = fields.Dict(allow_none=True)
+    template_params = fields.Dict(allow_none=True)
     filter_select_enabled = fields.Boolean()
     fetch_values_predicate = fields.String(allow_none=True)
-    extra = fields.String(allow_none=True)
+    extra = fields.Dict(allow_none=True)
     uuid = fields.UUID(required=True)
     columns = fields.List(fields.Nested(ImportV1ColumnSchema))
     metrics = fields.List(fields.Nested(ImportV1MetricSchema))