我怎么可以忽略JSON反序列化过程中未知的枚举值? [英] How can I ignore unknown enum values during json deserialization?
问题描述
如何才能Json.net不要扔了,当我的枚举不匹配JSON酒店所提供的字符串值?
How can I get Json.net not to throw up when my enum doesn't match string value provided in the json property?
这发生在我创建枚举根据目前的资料,但第三方API之后增加了更多的枚举值。
This happens when I create enum based on current documentation, but the third party API adds more enum values later.
我会很乐意与任何标记的特殊价值,未知或使用可空枚举和无与伦比的价值将返回null。
I would be happy with either marking special value as Unknown or using a nullable enum and unmatched value would return null.
推荐答案
您可以解决这个问题,一个自定义的 JsonConverter
。这是一个我放在一起利用来自Json.Net的 StringEnumConverter
类几块。它应该给你的灵活性来处理你决定什么办法的事情。下面是它如何工作的:
You can solve this problem with a custom JsonConverter
. Here is one I put together using a few pieces from the StringEnumConverter
class that comes from Json.Net. It should give you the flexibility to handle things whatever way you decide. Here's how it works:
- 如果在JSON中找到的值的枚举匹配(无论是作为一个字符串或整数),该值用过的。 (如果值为整数,存在多个可能的匹配,其中第一个被使用。)
- 否则,如果枚举类型可以为空,则该值设置为null。
- 否则,如果枚举有一个名为未知的值,则使用该值。
- 否则,枚举的第一个值被使用。
- If the value found in the JSON matches the enum (either as a string or an integer), that value is used. (If the value is integer and there are multiple possible matches, the first of those is used.)
- Otherwise if the enum type is nullable, then the value is set to null.
- Otherwise if the enum has a value called "Unknown", then that value is used.
- Otherwise the first value of the enum is used.
如果你不喜欢规则的工作方式,或者希望简化它,感觉自由。下面的代码:
If you don't like the way the rules work, or want to simplify it, feel free. Here's the code:
class TolerantEnumConverter : JsonConverter
{
public override bool CanConvert(Type objectType)
{
Type type = IsNullableType(objectType) ? Nullable.GetUnderlyingType(objectType) : objectType;
return type.IsEnum;
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
bool isNullable = IsNullableType(objectType);
Type enumType = isNullable ? Nullable.GetUnderlyingType(objectType) : objectType;
string[] names = Enum.GetNames(enumType);
if (reader.TokenType == JsonToken.String)
{
string enumText = reader.Value.ToString();
if (!string.IsNullOrEmpty(enumText))
{
string match = names
.Where(n => string.Equals(n, enumText, StringComparison.OrdinalIgnoreCase))
.FirstOrDefault();
if (match != null)
{
return Enum.Parse(enumType, match);
}
}
}
else if (reader.TokenType == JsonToken.Integer)
{
int enumVal = Convert.ToInt32(reader.Value);
int[] values = (int[])Enum.GetValues(enumType);
if (values.Contains(enumVal))
{
return Enum.Parse(enumType, enumVal.ToString());
}
}
if (!isNullable)
{
string defaultName = names
.Where(n => string.Equals(n, "Unknown", StringComparison.OrdinalIgnoreCase))
.FirstOrDefault();
if (defaultName == null)
{
defaultName = names.First();
}
return Enum.Parse(enumType, defaultName);
}
return null;
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
writer.WriteValue(value.ToString());
}
private bool IsNullableType(Type t)
{
return (t.IsGenericType && t.GetGenericTypeDefinition() == typeof(Nullable<>));
}
}
下面是把它转换器通过其演示
Here is a demo which puts it the converter through its paces using a couple of different enums (one has an "Unknown" value, and the other does not):
[JsonConverter(typeof(TolerantEnumConverter))]
enum Status
{
Ready = 1,
Set = 2,
Go = 3
}
[JsonConverter(typeof(TolerantEnumConverter))]
enum Color
{
Red = 1,
Yellow = 2,
Green = 3,
Unknown = 99
}
class Foo
{
public Status NonNullableStatusWithValidStringValue { get; set; }
public Status NonNullableStatusWithValidIntValue { get; set; }
public Status NonNullableStatusWithInvalidStringValue { get; set; }
public Status NonNullableStatusWithInvalidIntValue { get; set; }
public Status NonNullableStatusWithNullValue { get; set; }
public Status? NullableStatusWithValidStringValue { get; set; }
public Status? NullableStatusWithValidIntValue { get; set; }
public Status? NullableStatusWithInvalidStringValue { get; set; }
public Status? NullableStatusWithInvalidIntValue { get; set; }
public Status? NullableStatusWithNullValue { get; set; }
public Color NonNullableColorWithValidStringValue { get; set; }
public Color NonNullableColorWithValidIntValue { get; set; }
public Color NonNullableColorWithInvalidStringValue { get; set; }
public Color NonNullableColorWithInvalidIntValue { get; set; }
public Color NonNullableColorWithNullValue { get; set; }
public Color? NullableColorWithValidStringValue { get; set; }
public Color? NullableColorWithValidIntValue { get; set; }
public Color? NullableColorWithInvalidStringValue { get; set; }
public Color? NullableColorWithInvalidIntValue { get; set; }
public Color? NullableColorWithNullValue { get; set; }
}
class Program
{
static void Main(string[] args)
{
string json = @"
{
""NonNullableStatusWithValidStringValue"" : ""Set"",
""NonNullableStatusWithValidIntValue"" : 2,
""NonNullableStatusWithInvalidStringValue"" : ""Blah"",
""NonNullableStatusWithInvalidIntValue"" : 9,
""NonNullableStatusWithNullValue"" : null,
""NullableStatusWithValidStringValue"" : ""Go"",
""NullableStatusWithValidIntValue"" : 3,
""NullableStatusWithNullValue"" : null,
""NullableStatusWithInvalidStringValue"" : ""Blah"",
""NullableStatusWithInvalidIntValue"" : 9,
""NonNullableColorWithValidStringValue"" : ""Green"",
""NonNullableColorWithValidIntValue"" : 3,
""NonNullableColorWithInvalidStringValue"" : ""Blah"",
""NonNullableColorWithInvalidIntValue"" : 0,
""NonNullableColorWithNullValue"" : null,
""NullableColorWithValidStringValue"" : ""Yellow"",
""NullableColorWithValidIntValue"" : 2,
""NullableColorWithNullValue"" : null,
""NullableColorWithInvalidStringValue"" : ""Blah"",
""NullableColorWithInvalidIntValue"" : 0,
}";
Foo foo = JsonConvert.DeserializeObject<Foo>(json);
foreach (PropertyInfo prop in typeof(Foo).GetProperties())
{
object val = prop.GetValue(foo, null);
Console.WriteLine(prop.Name + ": " +
(val == null ? "(null)" : val.ToString()));
}
}
}
输出:
Output:
NonNullableStatusWithValidStringValue: Set
NonNullableStatusWithValidIntValue: Set
NonNullableStatusWithInvalidStringValue: Ready
NonNullableStatusWithInvalidIntValue: Ready
NonNullableStatusWithNullValue: Ready
NullableStatusWithValidStringValue: Go
NullableStatusWithValidIntValue: Go
NullableStatusWithInvalidStringValue: (null)
NullableStatusWithInvalidIntValue: (null)
NullableStatusWithNullValue: (null)
NonNullableColorWithValidStringValue: Green
NonNullableColorWithValidIntValue: Green
NonNullableColorWithInvalidStringValue: Unknown
NonNullableColorWithInvalidIntValue: Unknown
NonNullableColorWithNullValue: Unknown
NullableColorWithValidStringValue: Yellow
NullableColorWithValidIntValue: Yellow
NullableColorWithInvalidStringValue: (null)
NullableColorWithInvalidIntValue: (null)
NullableColorWithNullValue: (null)
这篇关于我怎么可以忽略JSON反序列化过程中未知的枚举值?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!