ServiceStack.Text json反序列化创建错误的对象，而不是抛出无效的json输入字符串

Question

When I try to deserialise this invalid json string ( }] missing in the end) :

[{"ExtId":"2","Name":"VIP sj�lland","Mobiles":["4533333333","4544444444"]

By doing this:

var result = JsonSerializer.DeserializeFromString<T>(str);    

The ServiceStack json deserializer accepts the string, but it creates a wrong object, because I end up with a C# object having these values:

ExtId : "2"                                      // ok fine.
Name: "VIP sj�lland"                            // ok fine
Mobiles: ["4533333333","4544444444", "544444444"]// Aarg! An array with 3 objects ?!? 
                                                 // There were only two in the JSON string.

In this case it would be much better to have an exception thrown instead of continuing with bad data. Therefore I tried using:

JsConfig.ThrowOnDeserializationError = true; 

just before calling DeserializeFromString but no exception was thrown. In January I asked this question Configure ServiceStack.Text to throw on invalid JSON and the answer was that ServiceStack is favoring resilence and that I could make a pull request in GitHub.

Is this still the case? And have anyone done it already, saving me the trouble? Otherwise, I am on a very tight schedule, so if anyone has some code or suggestions for how to create an option-flag for making ServiceStack throw on deserialization errors, please reply here, so that I can get this done faster.

Answer 1

This is resolved in ServiceStack.Text v4+ which by default doesn't populate incomplete collections, eg:

public class Poco
{
    public string ExtId { get; set; }
    public string Name { get; set; }
    public string[] Mobiles { get; set; }
}

var json = "[{\"ExtId\":\"2\",\"Name\":\"VIP sj�lland\",\"Mobiles\":[\"4533333333\",\"4544444444\"]";

var dto = json.FromJson<Poco[]>();

Assert.That(dto[0].ExtId, Is.EqualTo("2"));
Assert.That(dto[0].Name, Is.EqualTo("VIP sj�lland"));
Assert.That(dto[0].Mobiles, Is.Null);

Or if preferred can throw on Error:

JsConfig.ThrowOnDeserializationError = true;

Assert.Throws<SerializationException>(() => 
    json.FromJson<Poco[]>());

Answer 2

C# is a little bit picky when it comes to JSON. Following would be valid ! Note i do not have anonymous object array as the default element.

{
    "ExtItem": [
        {
            "ExtId": "2",
            "Name": "VIPsj�lland",
            "Mobiles": [
                "4533333333",
                "4544444444"
            ]
        }
    ]
}

If i generate a POCO from this I get

public class Rootobject
{
    public Extitem[] ExtItem { get; set; }
}

public class Extitem
{
    public string ExtId { get; set; }
    public string Name { get; set; }
    public string[] Mobiles { get; set; }
}

I personally use extension method to string

public static class Extensions
{
    public  static bool DeserializeJson<T>(this String str, out T item)
    {
        item = default(T);
        try
        {
            item = new JavaScriptSerializer().Deserialize<T>(str);
            return true;
        }
        catch (Exception ex)
        {
            return false;
        }
    }
}

This would enable me to write:

Rootobject ext;
const string validJson = @"
{
    ""ExtItem"": [
        {
            ""ExtId"":""2"",
            ""Name"":""VIPsj�lland"",
            ""Mobiles"":[
                ""4533333333"",
                ""4544444444""
            ]
        }
    ]
}";
if (validJson.DeserializeJson(out ext))
{ //valid input 
    // following would print 2 elements : 4533333333, 4544444444
    Console.WriteLine(string.Join(", ", ext.ExtItem.First().Mobiles)); 
} //invalid input

Answer 3

I tried this an have the exception thrown when I missed the } at the end.

In C#, the format for JSON is {"name", "value"} not [{"name", "value"}].

class M
        {
            public string ExtId { get; set; }
            public string Name { get; set; }
            public List<string> Mobiles { get; set; }
        }

string str = "{\"ExtId\":\"2\",\"Name\":\"VIP\",\"Mobiles\":[\"4533333333\",\"4544444444\"]";

M m = JsonConvert.DeserializeObject<M>(str);

When run this, you will get error as a } is missing.

Using:

string str = "{\"ExtId\":\"2\",\"Name\":\"VIP\",\"Mobiles\":[\"4533333333\",\"4544444444\"]}";

The object is deserialized fine.

You can see the JSON of this object from:

string s = JsonConvert.SerializeObject(m);

Answer 4

I just use the Newtonsoft.Json T JsonConvert.DeserializeObject<T>(string value) and it throws an exception;

If I use the object JsonConvert.DeserializeObject(string value) this one it creates the correct object by simply placing the missing }]

I found that this is a very reliable and fast library.