使自定义.NET Exception可序列化的正确方法是什么？
时间：2020-03-06 14:22:23 来源:igfitidea点击:
更具体地说，当异常包含自定义对象时，自定义对象本身可能可以序列化，也可以不可以序列化。
举个例子：
public class MyException : Exception
{
private readonly string resourceName;
private readonly IList<string> validationErrors;
public MyException(string resourceName, IList<string> validationErrors)
{
this.resourceName = resourceName;
this.validationErrors = validationErrors;
}
public string ResourceName
{
get { return this.resourceName; }
}
public IList<string> ValidationErrors
{
get { return this.validationErrors; }
}
}
如果将此Exception序列化并反序列化，则不会保留两个自定义属性(" ResourceName"和" ValidationErrors")。该属性将返回" null"。
是否存在用于实现自定义异常的序列化的通用代码模式？
解决方案
用[Serializable]标记类，尽管我不确定串行器将如何处理IList成员。
编辑
下面的帖子是正确的，因为自定义异常具有带参数的构造函数，因此我们必须实现ISerializable。
如果使用默认构造函数并使用getter / setter属性公开这两个自定义成员，则只需设置该属性即可。
实现ISerializable，并遵循正常模式进行操作。
我们需要使用[Serializable]属性标记该类，并添加对该接口的支持，还添加隐式构造函数(在该页面上进行描述，搜索隐式构造函数)。我们可以在文本下方的代码中看到其实现的示例。
我必须认为，要序列化异常是一个很强的迹象，表明我们对某些问题采用了错误的方法。最终目标是什么？如果要在两个进程之间或者同一进程的不同运行之间传递异常，则该异常的大多数属性无论如何在另一个进程中将无效。
在catch()语句中提取所需的状态信息并将其存档可能会更有意义。
异常已经可以序列化了，但是我们需要重写GetObjectData方法来存储变量并提供一个构造函数，该构造函数可以在为对象重新补水时调用。
因此，示例变为：
[Serializable()]
public class MyException : Exception
{
private readonly string resourceName;
private readonly IList<string> validationErrors;
public MyException(string resourceName, IList<string> validationErrors)
{
this.resourceName = resourceName;
this.validationErrors = validationErrors;
}
public string ResourceName
{
get { return this.resourceName; }
}
public IList<string> ValidationErrors
{
get { return this.validationErrors; }
}
[SecurityPermissionAttribute(SecurityAction.Demand, SerializationFormatter=true)]
protected MyException(SerializationInfo info, StreamingContext context) : base (info, context)
{
this.resourceName = info.GetString("MyException.ResourceName");
this.validationErrors = info.GetValue("MyException.ValidationErrors", typeof(IList<string>));
}
[SecurityPermissionAttribute(SecurityAction.Demand, SerializationFormatter=true)]
public override void GetObjectData(SerializationInfo info, StreamingContext context)
{
base.GetObjectData(info, context);
info.AddValue("MyException.ResourceName", this.ResourceName);
// Note: if "List<T>" isn't serializable you may need to work out another
// method of adding your list, this is just for show...
info.AddValue("MyException.ValidationErrors", this.ValidationErrors, typeof(IList<string>));
}
}
曾经有Eric Gunnerson在MSDN上发表的一篇精彩文章"脾气暴躁的异常"，但它似乎已被取消。该网址为：
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dncscol/html/csharp08162001.asp
艾德斯曼的答案是正确的，更多信息在这里：
http://msdn.microsoft.com/zh-CN/library/ms229064.aspx
我想不出具有非可序列化成员的Exception的任何用例，但是如果我们避免尝试在GetObjectData和反序列化构造函数中序列化/反序列化它们，则应该可以。还用[NonSerialized]属性标记它们，更多的是作为文档，而不是其他任何东西，因为我们自己实现序列化。
基本实现，无自定义属性
SerializableExceptionWithoutCustomProperties.cs：
namespace SerializableExceptions
{
using System;
using System.Runtime.Serialization;
[Serializable]
// Important: This attribute is NOT inherited from Exception, and MUST be specified
// otherwise serialization will fail with a SerializationException stating that
// "Type X in Assembly Y is not marked as serializable."
public class SerializableExceptionWithoutCustomProperties : Exception
{
public SerializableExceptionWithoutCustomProperties()
{
}
public SerializableExceptionWithoutCustomProperties(string message)
: base(message)
{
}
public SerializableExceptionWithoutCustomProperties(string message, Exception innerException)
: base(message, innerException)
{
}
// Without this constructor, deserialization will fail
protected SerializableExceptionWithoutCustomProperties(SerializationInfo info, StreamingContext context)
: base(info, context)
{
}
}
}
具有自定义属性的完整实现
完整实现自定义可序列化异常(" MySerializableException")和派生的"密封"异常(" MyDerivedSerializableException")。
有关此实现的要点总结如下：
- 我们必须使用Serializable属性修饰每个派生类。此属性不是从基类继承的，如果未指定，则序列化将失败，并带有
SerializationException，指出"未在程序集Y中标记X可序列化。" - 重写GetObjectData()并确保最后调用" base.GetObjectData(info，context)"，以便让基类保存其自己的状态。
SerializableExceptionWithCustomProperties.cs：
namespace SerializableExceptions
{
using System;
using System.Collections.Generic;
using System.Runtime.Serialization;
using System.Security.Permissions;
[Serializable]
// Important: This attribute is NOT inherited from Exception, and MUST be specified
// otherwise serialization will fail with a SerializationException stating that
// "Type X in Assembly Y is not marked as serializable."
public class SerializableExceptionWithCustomProperties : Exception
{
private readonly string resourceName;
private readonly IList<string> validationErrors;
public SerializableExceptionWithCustomProperties()
{
}
public SerializableExceptionWithCustomProperties(string message)
: base(message)
{
}
public SerializableExceptionWithCustomProperties(string message, Exception innerException)
: base(message, innerException)
{
}
public SerializableExceptionWithCustomProperties(string message, string resourceName, IList<string> validationErrors)
: base(message)
{
this.resourceName = resourceName;
this.validationErrors = validationErrors;
}
public SerializableExceptionWithCustomProperties(string message, string resourceName, IList<string> validationErrors, Exception innerException)
: base(message, innerException)
{
this.resourceName = resourceName;
this.validationErrors = validationErrors;
}
[SecurityPermissionAttribute(SecurityAction.Demand, SerializationFormatter = true)]
// Constructor should be protected for unsealed classes, private for sealed classes.
// (The Serializer invokes this constructor through reflection, so it can be private)
protected SerializableExceptionWithCustomProperties(SerializationInfo info, StreamingContext context)
: base(info, context)
{
this.resourceName = info.GetString("ResourceName");
this.validationErrors = (IList<string>)info.GetValue("ValidationErrors", typeof(IList<string>));
}
public string ResourceName
{
get { return this.resourceName; }
}
public IList<string> ValidationErrors
{
get { return this.validationErrors; }
}
[SecurityPermissionAttribute(SecurityAction.Demand, SerializationFormatter = true)]
public override void GetObjectData(SerializationInfo info, StreamingContext context)
{
if (info == null)
{
throw new ArgumentNullException("info");
}
info.AddValue("ResourceName", this.ResourceName);
// Note: if "List<T>" isn't serializable you may need to work out another
// method of adding your list, this is just for show...
info.AddValue("ValidationErrors", this.ValidationErrors, typeof(IList<string>));
// MUST call through to the base class to let it save its own state
base.GetObjectData(info, context);
}
}
}
DerivedSerializableExceptionWithAdditionalCustomProperties.cs：
namespace SerializableExceptions
{
using System;
using System.Collections.Generic;
using System.Runtime.Serialization;
using System.Security.Permissions;
[Serializable]
public sealed class DerivedSerializableExceptionWithAdditionalCustomProperty : SerializableExceptionWithCustomProperties
{
private readonly string username;
public DerivedSerializableExceptionWithAdditionalCustomProperty()
{
}
public DerivedSerializableExceptionWithAdditionalCustomProperty(string message)
: base(message)
{
}
public DerivedSerializableExceptionWithAdditionalCustomProperty(string message, Exception innerException)
: base(message, innerException)
{
}
public DerivedSerializableExceptionWithAdditionalCustomProperty(string message, string username, string resourceName, IList<string> validationErrors)
: base(message, resourceName, validationErrors)
{
this.username = username;
}
public DerivedSerializableExceptionWithAdditionalCustomProperty(string message, string username, string resourceName, IList<string> validationErrors, Exception innerException)
: base(message, resourceName, validationErrors, innerException)
{
this.username = username;
}
[SecurityPermissionAttribute(SecurityAction.Demand, SerializationFormatter = true)]
// Serialization constructor is private, as this class is sealed
private DerivedSerializableExceptionWithAdditionalCustomProperty(SerializationInfo info, StreamingContext context)
: base(info, context)
{
this.username = info.GetString("Username");
}
public string Username
{
get { return this.username; }
}
public override void GetObjectData(SerializationInfo info, StreamingContext context)
{
if (info == null)
{
throw new ArgumentNullException("info");
}
info.AddValue("Username", this.username);
base.GetObjectData(info, context);
}
}
}
单元测试
MSTest单元测试上面定义的三种异常类型。
UnitTests.cs：
namespace SerializableExceptions
{
using System;
using System.Collections.Generic;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;
using Microsoft.VisualStudio.TestTools.UnitTesting;
[TestClass]
public class UnitTests
{
private const string Message = "The widget has unavoidably blooped out.";
private const string ResourceName = "Resource-A";
private const string ValidationError1 = "You forgot to set the whizz bang flag.";
private const string ValidationError2 = "Wally cannot operate in zero gravity.";
private readonly List<string> validationErrors = new List<string>();
private const string Username = "Barry";
public UnitTests()
{
validationErrors.Add(ValidationError1);
validationErrors.Add(ValidationError2);
}
[TestMethod]
public void TestSerializableExceptionWithoutCustomProperties()
{
Exception ex =
new SerializableExceptionWithoutCustomProperties(
"Message", new Exception("Inner exception."));
// Save the full ToString() value, including the exception message and stack trace.
string exceptionToString = ex.ToString();
// Round-trip the exception: Serialize and de-serialize with a BinaryFormatter
BinaryFormatter bf = new BinaryFormatter();
using (MemoryStream ms = new MemoryStream())
{
// "Save" object state
bf.Serialize(ms, ex);
// Re-use the same stream for de-serialization
ms.Seek(0, 0);
// Replace the original exception with de-serialized one
ex = (SerializableExceptionWithoutCustomProperties)bf.Deserialize(ms);
}
// Double-check that the exception message and stack trace (owned by the base Exception) are preserved
Assert.AreEqual(exceptionToString, ex.ToString(), "ex.ToString()");
}
[TestMethod]
public void TestSerializableExceptionWithCustomProperties()
{
SerializableExceptionWithCustomProperties ex =
new SerializableExceptionWithCustomProperties(Message, ResourceName, validationErrors);
// Sanity check: Make sure custom properties are set before serialization
Assert.AreEqual(Message, ex.Message, "Message");
Assert.AreEqual(ResourceName, ex.ResourceName, "ex.ResourceName");
Assert.AreEqual(2, ex.ValidationErrors.Count, "ex.ValidationErrors.Count");
Assert.AreEqual(ValidationError1, ex.ValidationErrors[0], "ex.ValidationErrors[0]");
Assert.AreEqual(ValidationError2, ex.ValidationErrors[1], "ex.ValidationErrors[1]");
// Save the full ToString() value, including the exception message and stack trace.
string exceptionToString = ex.ToString();
// Round-trip the exception: Serialize and de-serialize with a BinaryFormatter
BinaryFormatter bf = new BinaryFormatter();
using (MemoryStream ms = new MemoryStream())
{
// "Save" object state
bf.Serialize(ms, ex);
// Re-use the same stream for de-serialization
ms.Seek(0, 0);
// Replace the original exception with de-serialized one
ex = (SerializableExceptionWithCustomProperties)bf.Deserialize(ms);
}
// Make sure custom properties are preserved after serialization
Assert.AreEqual(Message, ex.Message, "Message");
Assert.AreEqual(ResourceName, ex.ResourceName, "ex.ResourceName");
Assert.AreEqual(2, ex.ValidationErrors.Count, "ex.ValidationErrors.Count");
Assert.AreEqual(ValidationError1, ex.ValidationErrors[0], "ex.ValidationErrors[0]");
Assert.AreEqual(ValidationError2, ex.ValidationErrors[1], "ex.ValidationErrors[1]");
// Double-check that the exception message and stack trace (owned by the base Exception) are preserved
Assert.AreEqual(exceptionToString, ex.ToString(), "ex.ToString()");
}
[TestMethod]
public void TestDerivedSerializableExceptionWithAdditionalCustomProperty()
{
DerivedSerializableExceptionWithAdditionalCustomProperty ex =
new DerivedSerializableExceptionWithAdditionalCustomProperty(Message, Username, ResourceName, validationErrors);
// Sanity check: Make sure custom properties are set before serialization
Assert.AreEqual(Message, ex.Message, "Message");
Assert.AreEqual(ResourceName, ex.ResourceName, "ex.ResourceName");
Assert.AreEqual(2, ex.ValidationErrors.Count, "ex.ValidationErrors.Count");
Assert.AreEqual(ValidationError1, ex.ValidationErrors[0], "ex.ValidationErrors[0]");
Assert.AreEqual(ValidationError2, ex.ValidationErrors[1], "ex.ValidationErrors[1]");
Assert.AreEqual(Username, ex.Username);
// Save the full ToString() value, including the exception message and stack trace.
string exceptionToString = ex.ToString();
// Round-trip the exception: Serialize and de-serialize with a BinaryFormatter
BinaryFormatter bf = new BinaryFormatter();
using (MemoryStream ms = new MemoryStream())
{
// "Save" object state
bf.Serialize(ms, ex);
// Re-use the same stream for de-serialization
ms.Seek(0, 0);
// Replace the original exception with de-serialized one
ex = (DerivedSerializableExceptionWithAdditionalCustomProperty)bf.Deserialize(ms);
}
// Make sure custom properties are preserved after serialization
Assert.AreEqual(Message, ex.Message, "Message");
Assert.AreEqual(ResourceName, ex.ResourceName, "ex.ResourceName");
Assert.AreEqual(2, ex.ValidationErrors.Count, "ex.ValidationErrors.Count");
Assert.AreEqual(ValidationError1, ex.ValidationErrors[0], "ex.ValidationErrors[0]");
Assert.AreEqual(ValidationError2, ex.ValidationErrors[1], "ex.ValidationErrors[1]");
Assert.AreEqual(Username, ex.Username);
// Double-check that the exception message and stack trace (owned by the base Exception) are preserved
Assert.AreEqual(exceptionToString, ex.ToString(), "ex.ToString()");
}
}
}
