我一直在开发一个需要通过JSON文件保存和加载数据的项目。这个JSON文件包含其他对象的各种列表。然而，当我尝试反序列化文件时，会出现以下错误:
System.NotSupportedException: 不支持没有无参构造函数、只有一个有参数构造函数或用 'JsonConstructorAttribute' 注释的带参数构造函数的类型的反序列化。
负责反序列化的代码如下:
public void LoadFromJson() {
int userCount = File.ReadAllLines(folder + "/users").Length;
int shopCount = File.ReadAllLines(folder + "/shops").Length;
using (FileStream fileUsers = File.Open(folder + "/users", FileMode.Open, FileAccess.Read)) {
StreamReader srUser = new StreamReader(fileUsers);
for(int i=0; i<userCount; i++){
ListOfUsers.Add(JsonSerializer.Deserialize<User>(srUser.ReadLine()));
}
srUser.Close();
fileUsers.Close();
}
using (FileStream fileShops = File.Open(folder + "/shops", FileMode.Open, FileAccess.Read)){
StreamReader srShops = new StreamReader(fileShops);
for(int i=0; i<shopCount; i++){
ListOfShops.Add(JsonSerializer.Deserialize<Shop>(srShops.ReadLine()));
}
srShops.Close();
fileShops.Close();
}
}
我尝试反序列化的类
public abstract class Shop{
public List<Sellable> ShopList { get; set; }
public int TotalValue { get; set; }
public string shopName { get; set; }
public Shop(List<Sellable> list, string shopname){
ShopList = list;
shopName = shopname;
}
public abstract bool AddToShop(Sellable item);
public abstract bool RemoveFromShop(string item);
public abstract int GetValue(string name);
public abstract string PrintShop();
}
public abstract class Furniture : Sellable{
public int Space { get; set; }
public Conditions Condition { get; set; }
public Materials Material { get; set; }
[JsonConstructorAttribute]
public Furniture(int val, int spc, string nm, Conditions condition, Materials material) : base (val, nm){
Space = spc;
Condition = condition;
Material = material;
}
}
public abstract class Sellable{
public int Value { get; set; }
public string Name { get; set; }
[JsonConstructorAttribute]
public Sellable(int val, string name){
Value = val;
Name = name;
}
Json转换器
public class SellableConverter : JsonConverter<Sellable>{
public enum Type{
Sellable,
Furniture,
Wearable,
}
public override Sellable Read(ref Utf8JsonReader reader, System.Type typeToConvert, JsonSerializerOptions options)
{
if (reader.TokenType != JsonTokenType.StartObject) throw new JsonException();
if (!reader.Read()
|| reader.TokenType != JsonTokenType.PropertyName
|| reader.GetString() != "Type") throw new JsonException();
if (!reader.Read() || reader.TokenType != JsonTokenType.Number) throw new JsonException();
Sellable baseClass;
Type typeDiscriminator = (Type)reader.GetInt32();
switch (typeDiscriminator)
{
case Type.Furniture:
if (!reader.Read() || reader.GetString() != "TypeValue") throw new JsonException();
if (!reader.Read() || reader.TokenType != JsonTokenType.StartObject) throw new JsonException();
baseClass = (Furniture.Furniture)JsonSerializer.Deserialize(ref reader, typeof(Furniture.Furniture), options);
break;
case Type.Wearable:
if (!reader.Read() || reader.GetString() != "TypeValue") throw new JsonException();
if (!reader.Read() || reader.TokenType != JsonTokenType.StartObject) throw new JsonException();
baseClass = (Wearable)JsonSerializer.Deserialize(ref reader, typeof(Wearable), options);
break;
case Type.Sellable:
if (!reader.Read() || reader.GetString() != "TypeValue") throw new JsonException();
if (!reader.Read() || reader.TokenType != JsonTokenType.StartObject) throw new JsonException();
baseClass = (Sellable)JsonSerializer.Deserialize(ref reader, typeof(Sellable));
break;
default:
throw new NotSupportedException();
}
if (!reader.Read() || reader.TokenType != JsonTokenType.EndObject) throw new JsonException();
return baseClass;
}
public override void Write(Utf8JsonWriter writer, Sellable value, JsonSerializerOptions options)
{
writer.WriteStartObject();
if (value is Furniture.Furniture derivedA)
{
writer.WriteNumber("TypeDiscriminator", (int)Type.Furniture);
writer.WritePropertyName("TypeValue");
JsonSerializer.Serialize(writer, derivedA, options);
}
else if (value is Wearable derivedB)
{
writer.WriteNumber("TypeDiscriminator", (int)Type.Wearable);
writer.WritePropertyName("TypeValue");
JsonSerializer.Serialize(writer, derivedB, options);
}
else if (value is Sellable baseClass)
{
writer.WriteNumber("TypeDiscriminator", (int)Type.Sellable);
writer.WritePropertyName("TypeValue");
JsonSerializer.Serialize(writer, baseClass);
}
else throw new NotSupportedException();
writer.WriteEndObject();
}
}
SaveToJson 方法：
public void SaveToJson(){
FileStream fileUsers;
FileStream fileShops;
if(!(File.Exists(folder + "/users"))) fileUsers = File.Create(folder + "/users");
else fileUsers = File.OpenWrite(folder + "/users");
if(!(File.Exists(folder + "/shops"))) fileShops = File.Create(folder + "/shops");
else fileShops = File.OpenWrite(folder + "/shops");
StreamWriter srUser = new StreamWriter(fileUsers);
StreamWriter srShop = new StreamWriter(fileShops);
var serializeOptions = new JsonSerializerOptions();
serializeOptions.Converters.Add(new SellableConverter());
for(int i=0; i<ListOfUsers.Count; i++){
srUser.WriteLine(JsonSerializer.Serialize<User>(ListOfUsers[i]), serializeOptions);
Console.WriteLine("Debug: " + "\n" + "Object: " + ListOfUsers[i] + "\n" + "Json: " + JsonSerializer.Serialize<User>(ListOfUsers[i]));
}
for(int i=0; i<ListOfShops.Count; i++){
srShop.WriteLine(JsonSerializer.Serialize<Shop>(ListOfShops[i]), serializeOptions);
Console.WriteLine("Debug: " + "\n" + "Object: " + ListOfShops[i] + "\n" + "Json: " + JsonSerializer.Serialize<Shop>(ListOfShops[i]));
}
srUser.Close();
fileUsers.Close();
srShop.Close();
fileShops.Close();
}
我该如何修复它？提前谢谢！:)
编辑：我添加了我正在尝试反序列化的类。如果我没有给出足够的细节或犯了愚蠢的错误，请见谅，我还是一名学生，并且第一次尝试处理大部分这些问题。
Shop。但是请参阅如何使用不可变类型和非公共访问器与System.Text.Json，以了解如何处理没有公共无参数构造函数的类型。 - dbc