我正在使用Newtonsoft JSON序列化程序，它适用于大多数对象。
不幸的是，当我尝试序列化一个大对象时，我得到一个JsonSerializationException，其中一个成员会抛出一个NullReferenceException。
无论如何都要忽略违规成员并序列化对象的其余部分？
我在想JsonSerializerSettings？
以下是我想要做的简化版本：
private class TestExceptionThrowingClass
{
public string Name { get { return "The Name"; } }
public string Address { get { throw new NullReferenceException(); } }
public int Age { get { return 30; } }
}
[Test]
public void CanSerializeAClassWithAnExceptionThrowingMember()
{
// Arrange
var toSerialize = new TestExceptionThrowingClass();
// Act
var serializerSettings = new Newtonsoft.Json.JsonSerializerSettings();
serializerSettings.MaxDepth = 5;
serializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
serializerSettings.MissingMemberHandling = Newtonsoft.Json.MissingMemberHandling.Ignore;
serializerSettings.NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore;
serializerSettings.ObjectCreationHandling = Newtonsoft.Json.ObjectCreationHandling.Reuse;
serializerSettings.DefaultValueHandling = Newtonsoft.Json.DefaultValueHandling.Ignore;
var result = Newtonsoft.Json.JsonConvert.SerializeObject(toSerialize);
// Assert
Assert.That(result, Is.EqualTo(@"{""Name"":""The Name"",""Age"":30}"));
}
这是堆栈跟踪：
at Newtonsoft.Json.Serialization.DynamicValueProvider.GetValue(Object target)
at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.CalculatePropertyValues(JsonWriter writer, Object value, JsonContainerContract contract, JsonProperty member, JsonProperty property, JsonContract& memberContract, Object& memberValue)
at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeObject(JsonWriter writer, Object value, JsonObjectContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty)
at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue(JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty)
at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize(JsonWriter jsonWriter, Object value, Type objectType)
at Newtonsoft.Json.JsonSerializer.SerializeInternal(JsonWriter jsonWriter, Object value, Type objectType)
at Newtonsoft.Json.JsonConvert.SerializeObject(Object value, Type type, Formatting formatting, JsonSerializerSettings settings)
at Newtonsoft.Json.JsonConvert.SerializeObject(Object value)
at AspectsProject.Aspects.CachingPolicy.CachingPolicyCacheKeyCreatorTests.CanSerializeAClassWithAnExceptionThrowingMember() in D:\Dev\test.cs:line 169
--NullReferenceException
at AspectsProject.Aspects.CachingPolicy.CachingPolicyCacheKeyCreatorTests.TestExceptionThrowingClass.get_Address() in D:\Dev\test.cs:line 149
at GetAddress(Object )
at Newtonsoft.Json.Serialization.DynamicValueProvider.GetValue(Object target)
我很高兴使用不同的JSON序列化程序，如果有人知道会这样做。
答案 0 :(得分：39)
忽略错误的简单方法：
JsonSerializerSettings settings = new JsonSerializerSettings();
settings.Error = (serializer,err) => {
err.ErrorContext.Handled = true;
}
或
settings.Error = (serializer,err) => err.ErrorContext.Handled = true;
答案 1 :(得分：27)
如果您不控制源代码，则可以使用自定义ContractResolver在序列化期间为有问题的属性注入“ShouldSerialize”方法。您可以让该方法始终返回false，或者可选地实现一些逻辑，该逻辑将检测属性将抛出的情况，并且仅在这种情况下返回false。
例如，假设您的课程如下：
class Problematic
{
public int Id { get; set; }
public string Name { get; set; }
public object Offender
{
get { throw new NullReferenceException(); }
}
}
显然，如果我们尝试序列化上述内容，它将无法工作，因为Offender属性将在序列化程序尝试访问它时始终抛出异常。由于我们知道导致问题的类和属性名称，因此我们可以编写自定义的ContractResolver（派生自DefaultContractResolver）以禁止该特定成员的序列化。
class CustomResolver : DefaultContractResolver
{
protected override JsonProperty CreateProperty(MemberInfo member,
MemberSerialization memberSerialization)
{
JsonProperty property = base.CreateProperty(member, memberSerialization);
if (property.DeclaringType == typeof(Problematic) &&
property.PropertyName == "Offender")
{
property.ShouldSerialize = instanceOfProblematic => false;
}
return property;
}
}
这是一个演示如何使用它的演示：
class Program
{
static void Main(string[] args)
{
Problematic obj = new Problematic
{
Id = 1,
Name = "Foo"
};
JsonSerializerSettings settings = new JsonSerializerSettings();
settings.ContractResolver = new CustomResolver();
string json = JsonConvert.SerializeObject(obj, settings);
Console.WriteLine(json);
}
}
输出：
{"Id":1,"Name":"Foo"}
在您的评论中，您表明您有多种对象可能会在访问任何属性时引发异常。为此，我们需要更通用的东西。这是一个可能适用于该情况的解析器，但您需要在自己的环境中进行广泛测试。它不依赖于任何特定的类或属性名称，而是为每个属性创建一个ShouldSerialize谓词。在该谓词中，它使用反射来获取try / catch中的属性值;如果成功则返回true，否则返回false。
class CustomResolver : DefaultContractResolver
{
protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
{
JsonProperty property = base.CreateProperty(member, memberSerialization);
property.ShouldSerialize = instance =>
{
try
{
PropertyInfo prop = (PropertyInfo)member;
if (prop.CanRead)
{
prop.GetValue(instance, null);
return true;
}
}
catch
{
}
return false;
};
return property;
}
}
这是一个演示：
class Program
{
static void Main(string[] args)
{
List<MightThrow> list = new List<MightThrow>
{
new MightThrow { Flags = ThrowFlags.None, Name = "none throw" },
new MightThrow { Flags = ThrowFlags.A, Name = "A throws" },
new MightThrow { Flags = ThrowFlags.B, Name = "B throws" },
new MightThrow { Flags = ThrowFlags.Both, Name = "both throw" },
};
JsonSerializerSettings settings = new JsonSerializerSettings();
settings.ContractResolver = new CustomResolver();
settings.Formatting = Formatting.Indented;
string json = JsonConvert.SerializeObject(list, settings);
Console.WriteLine(json);
}
}
[Flags]
enum ThrowFlags
{
None = 0,
A = 1,
B = 2,
Both = 3
}
class MightThrow
{
public string Name { get; set; }
public ThrowFlags Flags { get; set; }
public string A
{
get
{
if ((Flags & ThrowFlags.A) == ThrowFlags.A)
throw new Exception();
return "a";
}
}
public string B
{
get
{
if ((Flags & ThrowFlags.B) == ThrowFlags.B)
throw new Exception();
return "b";
}
}
}
输出：
[
{
"Name": "none throw",
"Flags": 0,
"A": "a",
"B": "b"
},
{
"Name": "A throws",
"Flags": 1,
"B": "b"
},
{
"Name": "B throws",
"Flags": 2,
"A": "a"
},
{
"Name": "both throw",
"Flags": 3
}
]