忽略序列化为JSON时引发异常的类成员
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，JsonSerializationException当我尝试序列化一个大对象时，我得到了一个，其中一个成员抛出NullReferenceException。
无论如何，有没有要忽略有问题的成员并序列化对象的其余部分？
我在想JsonSerializerSettings吗？
这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)
如果有人知道可以执行此操作，我很乐意使用其他JSON序列化程序。
回答：
如果您不控制源代码，则可以ContractResolver在序列化过程中使用自定义为有问题的属性注入“
ShouldSerialize”方法。您可以使该方法始终返回false，或者可以选择实现一些逻辑，该逻辑将检测属性将仅在这种情况下抛出并返回false的情况。
例如，假设您的类如下所示：
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，它将无法正常工作，因为Offender当序列化程序尝试访问该属性时，该属性始终会引发异常。由于我们知道引起问题的类和属性名称，因此我们可以编写一个自定义ContractResolver（派生自DefaultContractResolver）来抑制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"}回答：
在您的评论中，您指出了当访问任何属性时，您可能会抛出多种异常的对象。为此，我们需要更通用的东西。这是一个可能适用于这种情况的解析器，但是您需要在自己的环境中进行广泛的测试。它不依赖于任何特定的类或属性名称，而是为
每个 以其方式出现的属性创建ShouldSerialize谓词。在该谓词中，它使用反射来获取try /
catch内的属性的值。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
}
]
以上是 忽略序列化为JSON时引发异常的类成员 的全部内容， 来源链接： utcz.com/qa/406332.html
