How to parse a complex dynamic JSON, store it in the local db and display the data in flutter?

I used a Json Helper tool: https://app.quicktype.io/ , it can be cleaned up, but is getting all the data into the logical objects, after that, you can use a NOSQL database like https://pub.dev/packages/objectbox

Future<void> readJson() async {
    final String response = await rootBundle.loadString('assets/example.json');
    final data = await json.decode(response);
    final MetaData metaData = MetaData.fromJson(data);
    //print(metaData);
   
    final box = store.box<MetaData >();
   // Put a new object into the box

    final id = box.put(metaData);

   // Get the object back from the box
    final newMeta = box.get(id)!;   
}

The objects:

class MetaData {
  Meta meta;

  MetaData({
    required this.meta,
  });

  factory MetaData.fromRawJson(String str) =>
      MetaData.fromJson(json.decode(str));

  String toRawJson() => json.encode(toJson());

  factory MetaData.fromJson(Map<String, dynamic> json) => MetaData(
        meta: Meta.fromList(json["meta"]),
      );

  Map<String, dynamic> toJson() => {
        "meta": meta.toJson(),
      };
}

class Meta {
  General general;
  MorphologicalCharacteristic morphologicalCharacteristics;
  AgronomicalCharacteristic agronomicalCharacteristics;
  NutritionalAndOtherQuality nutritionalAndOtherQualities;
  SpecialIdentifyingCharacteristic specialIdentifyingCharacteristics;
  Imagearray imagearray;

  Meta({
    required this.general,
    required this.morphologicalCharacteristics,
    required this.agronomicalCharacteristics,
    required this.nutritionalAndOtherQualities,
    required this.specialIdentifyingCharacteristics,
    required this.imagearray,
  });

  factory Meta.fromRawJson(String str) => Meta.fromJson(json.decode(str));

  String toRawJson() => json.encode(toJson());

  factory Meta.fromJson(Map<String, dynamic> json) => Meta(
        general: General.fromList(json["General"]),
        morphologicalCharacteristics: MorphologicalCharacteristic.fromList(
            json["Morphological Characteristics"]),
        agronomicalCharacteristics: AgronomicalCharacteristic.fromList(
            json["Agronomical Characteristics"]),
        nutritionalAndOtherQualities: NutritionalAndOtherQuality.fromList(
            json["Nutritional and Other Qualities"]),
        specialIdentifyingCharacteristics:
            SpecialIdentifyingCharacteristic.fromList(
                json["Special Identifying Characteristics"]),
        imagearray: Imagearray.fromList(json["imagearray"]),
      );

  factory Meta.fromList(List<dynamic> json) => Meta(
        general: General.fromList(json[0]["General"]),
        morphologicalCharacteristics: MorphologicalCharacteristic.fromList(
            json[1]["Morphological Characteristics"]),
        agronomicalCharacteristics: AgronomicalCharacteristic.fromList(
            json[2]["Agronomical Characteristics"]),
        nutritionalAndOtherQualities: NutritionalAndOtherQuality.fromList(
            json[3]["Nutritional and Other Qualities"]),
        specialIdentifyingCharacteristics:
            SpecialIdentifyingCharacteristic.fromList(
                json[4]["Special Identifying Characteristics"]),
        imagearray: Imagearray.fromList(json[5]["imagearray"]),
      );

  Map<String, dynamic> toJson() => {
        "General": general.toJson(),
        "Morphological Characteristics": morphologicalCharacteristics.toJson(),
        "Agronomical Characteristics": agronomicalCharacteristics.toJson(),
        "Nutritional and Other Qualities":
            nutritionalAndOtherQualities.toJson(),
        "Special Identifying Characteristics":
            specialIdentifyingCharacteristics.toJson(),
        "imagearray": imagearray.toJson(),
      };
}

class AgronomicalCharacteristic {
  String averageHeightCm;
  String maturingDaysDays;
  String pinacleDaysDays;
  String quantityOfTiler;
  String resistantCharacteristics;
  String weightOfThousandGrainsGram;
  String yieldTonHa;

  AgronomicalCharacteristic({
    required this.averageHeightCm,
    required this.maturingDaysDays,
    required this.pinacleDaysDays,
    required this.quantityOfTiler,
    required this.resistantCharacteristics,
    required this.weightOfThousandGrainsGram,
    required this.yieldTonHa,
  });

  factory AgronomicalCharacteristic.fromRawJson(String str) =>
      AgronomicalCharacteristic.fromJson(json.decode(str));

  String toRawJson() => json.encode(toJson());

  factory AgronomicalCharacteristic.fromJson(Map<String, dynamic> json) =>
      AgronomicalCharacteristic(
        averageHeightCm: json["Average Height (cm)"],
        maturingDaysDays: json["Maturing Days (days)"],
        pinacleDaysDays: json["Pinacle days (days)"],
        quantityOfTiler: json["Quantity of tiler"],
        resistantCharacteristics: json["Resistant Characteristics"],
        weightOfThousandGrainsGram: json["Weight of Thousand grains (gram)"],
        yieldTonHa: json["Yield (ton/ha)"],
      );

  factory AgronomicalCharacteristic.fromList(List<dynamic> json) =>
      AgronomicalCharacteristic(
        averageHeightCm: json[0]["Average Height (cm)"],
        maturingDaysDays: json[1]["Maturing Days (days)"],
        pinacleDaysDays: json[2]["Pinacle days (days)"],
        quantityOfTiler: json[3]["Quantity of tiler"],
        resistantCharacteristics: json[4]["Resistant Characteristics"],
        weightOfThousandGrainsGram: json[5]["Weight of Thousand grains (gram)"],
        yieldTonHa: json[6]["Yield (ton/ha)"],
      );

  Map<String, dynamic> toJson() => {
        "Average Height (cm)": averageHeightCm,
        "Maturing Days (days)": maturingDaysDays,
        "Pinacle days (days)": pinacleDaysDays,
        "Quantity of tiler": quantityOfTiler,
        "Resistant Characteristics": resistantCharacteristics,
        "Weight of Thousand grains (gram)": weightOfThousandGrainsGram,
        "Yield (ton/ha)": yieldTonHa,
      };
}

class General {
  String nameBeforeRelease;
  String releasedYear;
  String recommendedAreas;

  General({
    required this.nameBeforeRelease,
    required this.releasedYear,
    required this.recommendedAreas,
  });

  factory General.fromRawJson(String str) => General.fromJson(json.decode(str));

  String toRawJson() => json.encode(toJson());

  factory General.fromJson(Map<String, dynamic> json) => General(
        nameBeforeRelease: json["Name before Release"],
        releasedYear: json["Released Year"],
        recommendedAreas: json["Recommended Areas"],
      );

  factory General.fromList(List<dynamic> json) => General(
        nameBeforeRelease: json[0]["Name before Release"],
        releasedYear: json[1]["Released Year"],
        recommendedAreas: json[2]["Recommended Areas"],
      );

  Map<String, dynamic> toJson() => {
        "Name before Release": nameBeforeRelease,
        "Released Year": releasedYear,
        "Recommended Areas": recommendedAreas,
      };
}

class Imagearray {
  String aditya16YWkYQd;
  String adityaCapture2LuAqweK;
  String adityaCapture3DsU6RNl;
  String adityaCapture4VgvD6R0;

  Imagearray({
    required this.aditya16YWkYQd,
    required this.adityaCapture2LuAqweK,
    required this.adityaCapture3DsU6RNl,
    required this.adityaCapture4VgvD6R0,
  });

  factory Imagearray.fromRawJson(String str) =>
      Imagearray.fromJson(json.decode(str));

  String toRawJson() => json.encode(toJson());

  factory Imagearray.fromJson(Map<String, dynamic> json) => Imagearray(
        aditya16YWkYQd: json["Aditya_1_6YWkYQd"],
        adityaCapture2LuAqweK: json["Aditya_Capture_2_LuAqweK"],
        adityaCapture3DsU6RNl: json["Aditya_Capture3_dsU6RNl"],
        adityaCapture4VgvD6R0: json["Aditya_Capture4_vgvD6R0"],
      );

  factory Imagearray.fromList(List<dynamic> json) => Imagearray(
        aditya16YWkYQd: json[0]["Aditya_1_6YWkYQd"],
        adityaCapture2LuAqweK: json[1]["Aditya_Capture_2_LuAqweK"],
        adityaCapture3DsU6RNl: json[2]["Aditya_Capture3_dsU6RNl"],
        adityaCapture4VgvD6R0: json[3]["Aditya_Capture4_vgvD6R0"],
      );

  Map<String, dynamic> toJson() => {
        "Aditya_1_6YWkYQd": aditya16YWkYQd,
        "Aditya_Capture_2_LuAqweK": adityaCapture2LuAqweK,
        "Aditya_Capture3_dsU6RNl": adityaCapture3DsU6RNl,
        "Aditya_Capture4_vgvD6R0": adityaCapture4VgvD6R0,
      };
}

class MorphologicalCharacteristic {
  String colorOfSeed;
  String glaucosityOfFlagLeafSheath;
  String pinnacleType;
  String presenceOfPurpleColourInOuterAuricleOfFlaggedLeaf;
  String ripenPinnacleColour;
  String shapeOfSeed;
  String shineOfPennicleOfWheatEarGlaucosity;

  MorphologicalCharacteristic({
    required this.colorOfSeed,
    required this.glaucosityOfFlagLeafSheath,
    required this.pinnacleType,
    required this.presenceOfPurpleColourInOuterAuricleOfFlaggedLeaf,
    required this.ripenPinnacleColour,
    required this.shapeOfSeed,
    required this.shineOfPennicleOfWheatEarGlaucosity,
  });

  factory MorphologicalCharacteristic.fromRawJson(String str) =>
      MorphologicalCharacteristic.fromJson(json.decode(str));

  String toRawJson() => json.encode(toJson());

  factory MorphologicalCharacteristic.fromJson(Map<String, dynamic> json) =>
      MorphologicalCharacteristic(
        colorOfSeed: json["Color of Seed"],
        glaucosityOfFlagLeafSheath: json["Glaucosity of Flag Leaf Sheath"],
        pinnacleType: json["Pinnacle Type"],
        presenceOfPurpleColourInOuterAuricleOfFlaggedLeaf:
            json["Presence of Purple Colour in Outer Auricle of Flagged-Leaf"],
        ripenPinnacleColour: json["Ripen Pinnacle Colour"],
        shapeOfSeed: json["Shape of Seed"],
        shineOfPennicleOfWheatEarGlaucosity:
            json["Shine of Pennicle of Wheat (Ear Glaucosity)"],
      );

  factory MorphologicalCharacteristic.fromList(List<dynamic> json) =>
      MorphologicalCharacteristic(
        colorOfSeed: json[0]["Color of Seed"],
        glaucosityOfFlagLeafSheath: json[1]["Glaucosity of Flag Leaf Sheath"],
        pinnacleType: json[2]["Pinnacle Type"],
        presenceOfPurpleColourInOuterAuricleOfFlaggedLeaf: json[3]
            ["Presence of Purple Colour in Outer Auricle of Flagged-Leaf"],
        ripenPinnacleColour: json[4]["Ripen Pinnacle Colour"],
        shapeOfSeed: json[5]["Shape of Seed"],
        shineOfPennicleOfWheatEarGlaucosity: json[6]
            ["Shine of Pennicle of Wheat (Ear Glaucosity)"],
      );

  Map<String, dynamic> toJson() => {
        "Color of Seed": colorOfSeed,
        "Glaucosity of Flag Leaf Sheath": glaucosityOfFlagLeafSheath,
        "Pinnacle Type": pinnacleType,
        "Presence of Purple Colour in Outer Auricle of Flagged-Leaf":
            presenceOfPurpleColourInOuterAuricleOfFlaggedLeaf,
        "Ripen Pinnacle Colour": ripenPinnacleColour,
        "Shape of Seed": shapeOfSeed,
        "Shine of Pennicle of Wheat (Ear Glaucosity)":
            shineOfPennicleOfWheatEarGlaucosity,
      };
}

class NutritionalAndOtherQuality {
  String percentageOfProtein;

  NutritionalAndOtherQuality({
    required this.percentageOfProtein,
  });

  factory NutritionalAndOtherQuality.fromRawJson(String str) =>
      NutritionalAndOtherQuality.fromJson(json.decode(str));

  String toRawJson() => json.encode(toJson());

  factory NutritionalAndOtherQuality.fromJson(Map<String, dynamic> json) =>
      NutritionalAndOtherQuality(
        percentageOfProtein: json["Percentage of Protein (%)"],
      );

  factory NutritionalAndOtherQuality.fromList(List<dynamic> json) =>
      NutritionalAndOtherQuality(
        percentageOfProtein: json[0]["Percentage of Protein (%)"],
      );

  Map<String, dynamic> toJson() => {
        "Percentage of Protein (%)": percentageOfProtein,
      };
}

class SpecialIdentifyingCharacteristic {
  String specialDescription;

  SpecialIdentifyingCharacteristic({
    required this.specialDescription,
  });

  factory SpecialIdentifyingCharacteristic.fromRawJson(String str) =>
      SpecialIdentifyingCharacteristic.fromJson(json.decode(str));

  String toRawJson() => json.encode(toJson());

  factory SpecialIdentifyingCharacteristic.fromJson(
          Map<String, dynamic> json) =>
      SpecialIdentifyingCharacteristic(
        specialDescription: json["Special Description"],
      );
  factory SpecialIdentifyingCharacteristic.fromList(List<dynamic> json) =>
      SpecialIdentifyingCharacteristic(
        specialDescription: json[0]["Special Description"],
      );

  Map<String, dynamic> toJson() => {
        "Special Description": specialDescription,
      };
}