feat: add JSON DUMP/RESTORE support via type coercion to String

- Map JSON type to RDBTypeString (type 0) for Redis compatibility
- Serialize JSON to string representation during DUMP
- RESTORE creates String type (similar to SortedInt → Set pattern)
- Add TestDump_JSON following existing test patterns
- Type changes: ReJSON-RL → string after RESTORE (trade-off for compatibility)

Author: Zakir032002

src/storage/rdb/rdb.cc

@@ -35,6 +35,7 @@
 #include "types/redis_bitmap.h"
 #include "types/redis_bitmap_string.h"
 #include "types/redis_hash.h"
+#include "types/redis_json.h"
 #include "types/redis_list.h"
 #include "types/redis_set.h"
 #include "types/redis_sortedint.h"
@@ -723,7 +724,7 @@ Status RDB::Dump(const std::string &key, const RedisType type) {
 
 Status RDB::SaveObjectType(const RedisType type) {
   int robj_type = -1;
-  if (type == kRedisString || type == kRedisBitmap) {
+  if (type == kRedisString || type == kRedisBitmap || type == kRedisJson) {
     robj_type = RDBTypeString;
   } else if (type == kRedisHash) {
     robj_type = RDBTypeHash;
@@ -798,6 +799,20 @@ Status RDB::SaveObject(const std::string &key, const RedisType type) {
       return {Status::RedisExecErr, s.ToString()};
     }
     return SaveStringObject(value);
+  } else if (type == kRedisJson) {
+    redis::Json json_db(storage_, ns_);
+    JsonValue value;
+    auto s = json_db.Get(ctx, key, {}, &value);
+    if (!s.ok() && !s.IsNotFound()) {
+      return {Status::RedisExecErr, s.ToString()};
+    }
+    std::string json_str;
+    Config *config = storage_->GetConfig();
+    auto dump_status = value.Dump(&json_str, config->json_max_nesting_depth);
+    if (!dump_status.IsOK()) {
+      return {Status::RedisExecErr, dump_status.Msg()};
+    }
+    return SaveStringObject(json_str);
   } else if (type == kRedisSortedint) {
     redis::Sortedint sortedint_db(storage_, ns_);
     std::vector<uint64_t> ids;

tests/gocase/unit/dump/dump_test.go

@@ -220,3 +220,32 @@ func TestDump_SortedInt(t *testing.T) {
 	expectedMembers := []string{"5", "12", "23", "89", "100"}
 	require.ElementsMatch(t, expectedMembers, members)
 }
+
+func TestDump_JSON(t *testing.T) {
+	srv := util.StartServer(t, map[string]string{})
+	defer srv.Close()
+
+	ctx := context.Background()
+	rdb := srv.NewClient()
+	defer func() { require.NoError(t, rdb.Close()) }()
+
+	key := "test_json_key"
+
+	jsonData := `{"name":"Alice","age":30,"city":"NYC"}`
+	require.NoError(t, rdb.Do(ctx, "JSON.SET", key, "$", jsonData).Err())
+
+	require.EqualValues(t, "ReJSON-RL", rdb.Type(ctx, key).Val())
+
+	serialized, err := rdb.Dump(ctx, key).Result()
+	require.NoError(t, err)
+
+	restoredKey := fmt.Sprintf("restore_%s", key)
+	require.NoError(t, rdb.RestoreReplace(ctx, restoredKey, 0, serialized).Err())
+
+	require.EqualValues(t, "string", rdb.Type(ctx, restoredKey).Val())
+
+	content := rdb.Get(ctx, restoredKey).Val()
+	require.Contains(t, content, "Alice")
+	require.Contains(t, content, "30")
+	require.Contains(t, content, "NYC")
+}