c# - Newtonsoft.Json 解析不正确的json

Question

我遇到了一个奇怪的问题:给定这样的字符串 {"text":"s","cursorPosition":189,"dataSource":"json_northwind", 这不是一个正确的 json，它仍然被成功解析。

这是类:

public class CompletionDataRequest
{
    public CompletionDataRequest(string text, int cursorPosition, string dataSource, string project)
    {
        Text = text;
        CursorPosition = cursorPosition;
        DataSource = dataSource;
        Project = project;
    }

    public string Text { get; }
    public int CursorPosition { get; }
    public string DataSource { get; }
    public string Project { get; }
}

这是一个意外成功的测试:

var s = @"{""text"":""s"",""cursorPosition"":189,""dataSource"":""json_northwind"",";
var request = JsonConvert.DeserializeObject<CompletionDataRequest>(s);
request.Text.Should().Be("s");
request.CursorPosition.Should().Be(189);
request.DataSource.Should().Be("json_northwind");
request.Project.Should().BeNull();

库是否有一些松散的解析规则或者这可能是一个错误？我是库版本9.0.1

Answer 1

更新

一个问题 Deserializing unclosed object succeeds when the object has a parameterized constructor. #1038为这个问题打开了。它已在 Json.NET release 10.0.1 中修复在变更集中0721bd4 .

原始答案

您在 Json.NET 中发现了一个错误。只有当您的对象是使用参数化构造函数构造时才会出现。如果我将您的对象修改为具有非参数化构造函数:

public class CompletionDataRequest
{
    public CompletionDataRequest(string text, int cursorPosition, string dataSource, string project)
    {
        Text = text;
        CursorPosition = cursorPosition;
        DataSource = dataSource;
        Project = project;
    }

    [JsonConstructor]
    private CompletionDataRequest()
    {
    }

    [JsonProperty]
    public string Text { get; private set; }
    [JsonProperty]
    public int CursorPosition { get; private set; }
    [JsonProperty]
    public string DataSource { get; private set; }
    [JsonProperty]
    public string Project { get; private set; }
}

然后 Json.NET 将正确抛出一个 JsonSerializationException。

错误原因如下。使用无参数构造函数创建对象时，Json.NET 首先构造对象，然后用 JsonSerializerInternalReader.PopulateObject() 填充它。 .此方法具有以下(简化的)逻辑:

    private object PopulateObject(object newObject, JsonReader reader, JsonObjectContract contract, JsonProperty member, string id)
    {
        bool finished = false;
        do
        {
            switch (reader.TokenType)
            {
                case JsonToken.PropertyName:
                {
                    // Read and process the property.
                }
                case JsonToken.EndObject:
                    finished = true;
                    break;
                case JsonToken.Comment:
                    // ignore
                    break;
                default:
                    throw JsonSerializationException.Create(reader, "Unexpected token when deserializing object: " + reader.TokenType);
            }
        } while (!finished && reader.Read());

        if (!finished)
        {
            ThrowUnexpectedEndException(reader, contract, newObject, "Unexpected end when deserializing object.");
        }

        return newObject;
     }

如您所见，有逻辑 if (!finished) 来验证对象是否实际关闭。

但是，当使用参数化构造函数创建对象时，会在构造对象之前读取属性，使用 JsonSerializerInternalReader.ResolvePropertyAndCreatorValues() :

    private List<CreatorPropertyContext> ResolvePropertyAndCreatorValues(JsonObjectContract contract, JsonProperty containerProperty, JsonReader reader, Type objectType)
    {
        List<CreatorPropertyContext> propertyValues = new List<CreatorPropertyContext>();
        bool exit = false;
        do
        {
            switch (reader.TokenType)
            {
                case JsonToken.PropertyName:
                    // Read and process the property.
                    break;
                case JsonToken.Comment:
                    break;
                case JsonToken.EndObject:
                    exit = true;
                    break;
                default:
                    throw JsonSerializationException.Create(reader, "Unexpected token when deserializing object: " + reader.TokenType);
            }
        } while (!exit && reader.Read());

        return propertyValues;
    }

如您所见，没有等效的检查 exit 是否为真。

一个问题 Deserializing unclosed object succeeds when the object has a parameterized constructor. #1038为此而开放。