我在反序列化发送到 azure 函数的 JSON 时遇到了一些问题。首先，我打算将一组密文类型的 post 发送到 azure，反序列化 JSON 以恢复我的数据，然后对该数据进行操作。我的类如下所示，名为 sampleClass，它具有类型为 Ciphertext 的属性 ciphertext :
[DataContract]
public class sampleClass
{
[DataMember]
public Ciphertext ciphertext { get; set; }
[JsonConstructor]
public sampleClass() { }
}
这是我尝试序列化/反序列化的类。
为了发布数据，我使用 HttpClient 并将其发布为 JSON，如下所示:
HttpResponseMessage response = await client.PostAsJsonAsync("api/Function1", cipher);
在我的azure函数中，我试图将Json作为流读取并将其反序列化为sampleClass[]，但是这给我带来了一个错误。
//Receive data from The Http PostRequest.
string requestBody = await new StreamReader(req.Body).ReadToEndAsync();
//De serialises to an object.
sampleClass[] array = JsonConvert.DeserializeObject<sampleClass[]>(requestBody);
抛出的错误如下所示:
Executed 'Function1' (Failed, Id=1be7633e-6b6a-4626-98b7-8fec98eac633) [11/02/2020 15:50:48] System.Private.CoreLib: Exception while executing function: Function1. Newtonsoft.Json: Unable to find a constructor to use for type Microsoft.Research.SEAL.Ciphertext. A class should either have a default constructor, one constructor with arguments or a constructor marked with the JsonConstructor attribute. Path '[0].ciphertext.CoeffModCount', line 1, position 32.
当我尝试反序列化 JSON 时抛出此错误，如何解决此问题？
最佳答案
您这里有几个问题。让我们按顺序排列它们。
首先，输入 Microsoft.Research.SEAL.Ciphertext 既没有无参数构造函数，也没有单参数构造函数，从 reference source 可以看出:
public class Ciphertext : NativeObject
{
public Ciphertext(MemoryPoolHandle pool = null)
{
// Contents omitted
}
public Ciphertext(SEALContext context, MemoryPoolHandle pool = null)
{
// Contents omitted
}
// Additional constructors, methods and members omitted.
第一个构造函数的参数是可选的，但这并不意味着它是无参数的，它只是意味着编译器在代码中不存在该值时提供该值。但是，当通过反射调用构造函数时(Json.NET 就是这样做的)，仍然需要提供一个值；参见 Reflection - Call constructor with parameters 了解详情。此类型缺乏真正的无参数构造函数，导致抛出 Newtonsoft.Json: Unable to find a constructor to use for type Microsoft.Research.SEAL.Ciphertext. 异常。
(评论中指出您的问题是 sampleClass 缺少默认构造函数，但该评论是错误的。)
因为您无法修改Ciphertext提供您自己的构造方法的标准方法是使用 CustomCreationConverter<T> 像这样:
public class CiphertextConverter : CustomCreationConverter<Ciphertext>
{
public override Ciphertext Create(Type objectType)
{
return new Ciphertext(); // Use the default value for the optional parameter
}
}
然后执行:
var settings = new JsonSerializerSettings
{
Converters = { new CiphertextConverter() },
};
var array = JsonConvert.DeserializeObject<sampleClass []>(requestBody, settings);
但是，这不起作用，这是您的下一个问题。由于Ciphertext的大部分公共(public)属性是只读的，无法从它们反序列化类型。
演示 fiddle #1 失败 here .
那么，该怎么办呢？事实证明，Ciphertext有两种方法
-
public long Save(Stream stream, ComprModeType? comprMode = null) -
public long Load(SEALContext context, Stream stream)
这些似乎允许我们序列化 Ciphertext到 MemoryStream ，然后使用如下转换器将内容作为 Base64 字符串插入到 JSON 中:
public class CiphertextConverter : JsonConverter<Ciphertext>
{
readonly SEALContext context;
public CiphertextConverter(SEALContext context) => this.context = context ?? throw new ArgumentNullException(nameof(context));
public override Ciphertext ReadJson(JsonReader reader, Type objectType, Ciphertext existingValue, bool hasExistingValue, JsonSerializer serializer)
{
var data = serializer.Deserialize<byte []>(reader);
if (data == null)
return null;
var cipherText = new Ciphertext();
using (var stream = new MemoryStream(data))
cipherText.Load(context, stream);
return cipherText;
}
public override void WriteJson(JsonWriter writer, Ciphertext value, JsonSerializer serializer)
{
using (var stream = new MemoryStream())
{
value.Save(stream, ComprModeType.Deflate); // TODO: test to see whether Deflate gives better size vs speed performance in practice.
writer.WriteValue(stream.ToArray());
}
}
}
然后在序列化和反序列化过程中使用转换器，如下所示:
var settings = new JsonSerializerSettings
{
Converters = { new CiphertextConverter(GlobalContext.Context) },
};
var array = JsonConvert.DeserializeObject<sampleClass []>(requestBody, settings);
但是等等——这个物体是什么GlobalContext.Context ？这给我们带来了第三个问题，即您需要兼容 SEALContext 客户端和服务器端的对象传递 Ciphertext然后通过序列化。现在，浏览Cloud Functions Demo演示应用程序，这似乎是一个正确的假设，因为该应用程序在客户端和服务器端都有兼容的上下文:
- 客户端:https://github.com/microsoft/SEAL-Demo/blob/master/CloudFunctionsDemo/ClientBasedFunctions/ClientBasedFunctions/GlobalProperties.cs
- 服务器端:https://github.com/microsoft/SEAL-Demo/blob/master/CloudFunctionsDemo/CloudBasedFunctions/CloudBasedFunctions/GlobalProperties.cs
所以我假设您也这样做。鉴于您这样做，上面的转换器应该用于序列化和反序列化。
出于测试目的，我调整了测试方法 CiphertextTests.SaveLoadTest() 和类(class) GlobalContext 来自https://github.com/microsoft/SEAL/tree/master/dotnet/tests创建以下测试工具:
public class TestClass
{
[TestMethod]
public void JsonNetSaveLoadTest()
{
Debug.WriteLine("Testing Json.NET");
Func<Ciphertext, SEALContext, Ciphertext> roundtrip = (cipher, context) =>
{
var clientArray = new [] { new sampleClass { ciphertext = cipher } };
var settings = new JsonSerializerSettings
{
Converters = { new CiphertextConverter(GlobalContext.Context) },
};
var requestBody = JsonConvert.SerializeObject(clientArray, settings);
Debug.Write(" ");
Debug.WriteLine(requestBody);
Debug.WriteLine(" requestBody.Length={0}", requestBody.Length);
var array = JsonConvert.DeserializeObject<sampleClass []>(requestBody, settings);
Assert.IsTrue(array.Length == clientArray.Length);
var reserializedJson = JsonConvert.SerializeObject(array, settings);
Debug.Write(" ");
Debug.WriteLine(reserializedJson);
Assert.IsTrue(requestBody == reserializedJson);
return array[0].ciphertext;
};
SaveLoadTest(roundtrip);
Console.WriteLine(" passed.");
}
// Adapted from https://github.com/microsoft/SEAL/blob/master/dotnet/tests/CiphertextTests.cs#L113
[TestMethod]
public void DirectSaveLoadTest()
{
Debug.WriteLine("Testing direct save and load:");
Func<Ciphertext, SEALContext, Ciphertext> roundtrip = (cipher, context) =>
{
Ciphertext loaded = new Ciphertext();
Assert.AreEqual(0ul, loaded.Size);
Assert.AreEqual(0ul, loaded.PolyModulusDegree);
Assert.AreEqual(0ul, loaded.CoeffModCount);
using (MemoryStream mem = new MemoryStream())
{
cipher.Save(mem);
mem.Seek(offset: 0, loc: SeekOrigin.Begin);
loaded.Load(context, mem);
}
return loaded;
};
SaveLoadTest(roundtrip);
Debug.WriteLine(" passed.");
}
// Adapted from https://github.com/microsoft/SEAL/blob/master/dotnet/tests/CiphertextTests.cs#L113
static void SaveLoadTest(Func<Ciphertext, SEALContext, Ciphertext> roundtrip)
{
SEALContext context = GlobalContext.Context;
KeyGenerator keygen = new KeyGenerator(context);
Encryptor encryptor = new Encryptor(context, keygen.PublicKey);
Plaintext plain = new Plaintext("2x^3 + 4x^2 + 5x^1 + 6");
Ciphertext cipher = new Ciphertext();
encryptor.Encrypt(plain, cipher);
Assert.AreEqual(2ul, cipher.Size);
Assert.AreEqual(8192ul, cipher.PolyModulusDegree);
Assert.AreEqual(4ul, cipher.CoeffModCount);
var loaded = roundtrip(cipher, context);
Assert.AreEqual(2ul, loaded.Size);
Assert.AreEqual(8192ul, loaded.PolyModulusDegree);
Assert.AreEqual(4ul, loaded.CoeffModCount);
Assert.IsTrue(ValCheck.IsValidFor(loaded, context));
ulong ulongCount = cipher.Size * cipher.PolyModulusDegree * cipher.CoeffModCount;
for (ulong i = 0; i < ulongCount; i++)
{
Assert.AreEqual(cipher[i], loaded[i]);
}
}
}
static class GlobalContext
{
// Copied from https://github.com/microsoft/SEAL/blob/master/dotnet/tests/GlobalContext.cs
static GlobalContext()
{
EncryptionParameters encParams = new EncryptionParameters(SchemeType.BFV)
{
PolyModulusDegree = 8192,
CoeffModulus = CoeffModulus.BFVDefault(polyModulusDegree: 8192)
};
encParams.SetPlainModulus(65537ul);
BFVContext = new SEALContext(encParams);
encParams = new EncryptionParameters(SchemeType.CKKS)
{
PolyModulusDegree = 8192,
CoeffModulus = CoeffModulus.BFVDefault(polyModulusDegree: 8192)
};
CKKSContext = new SEALContext(encParams);
}
public static SEALContext BFVContext { get; private set; } = null;
public static SEALContext CKKSContext { get; private set; } = null;
public static SEALContext Context => BFVContext;
}
工作演示 fiddle #2 here .
注释:
只要是public，就不需要标记
sampleClass的无参构造函数。与[JsonConstructor].根据测试，为
Ciphertext生成的 Base64 字符串似乎很长，每个Ciphertext大约 0.5 MB 。由于 Json.NET 在解析过程中完全具体化了每个字符串，因此它在处理如此大的字符串时效率并不高。如果超过 maximum effective string length，您将需要重新评估您的架构或经验large object heap fragmentation .
免责声明
我不是安全专家。我无法告诉你是否发送序列化Ciphertext通过网络可能会泄露信息。我也无法建议您如何选择合适的 SEALContext对于您的应用程序 - 甚至客户端和服务器端具有兼容的上下文是否可能泄漏信息。这个答案仅解释如何通过 Json.NET 序列化特定的 SEAL 对象。
关于c# - 无法将 Json 反序列化为类型，无法找到构造函数，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/60172952/