一、前言
这个星期参加了一个面试，面试中问到深浅拷贝的区别，然后我就简单了讲述了它们的之间的区别，然后面试官又继续问，如何实现一个深拷贝呢？当时只回答回答了一种方式，就是使用反射，然后面试官提示还可以通过反序列化和表达树的方式。然后又继续问，如果用反射来实现深拷贝的话，如何解决互相引用对象的问题呢？当时我给出的答案是说那就不用反射去实现呗，用反序列化实现呗，或者直接避免使两个对象互相引用呗。然后面试官说，如果一定用反射来写，你是怎么去解决这个问题呢？这时候我就愣住了。
这样也就有了这篇文章。今天就来深入解析下深浅拷贝的问题。.
二、深拷贝 Vs 浅拷贝
首先，讲到深浅拷贝，自然就有一个问题来了？什么是深拷贝，什么又是浅拷贝呢？下面就具体介绍下它们的定义。
深拷贝：指的是拷贝一个对象时，不仅仅把对象的引用进行复制，还把该对象引用的值也一起拷贝。这样进行深拷贝后的拷贝对象就和源对象互相独立，其中任何一个对象的改动都不会对另外一个对象造成影响。举个例子，一个人叫张三，然后使用克隆技术以张三来克隆另外一个人叫李四，这样张三和李四就是相互独立的，不管张三缺胳膊还是李四少腿了都不会影响另外一个人。在.NET领域，值对象就是典型的例子，如int, Double以及结构体和枚举等。具体例子如下所示：
int source = 123;// 值类型赋值内部执行深拷贝int copy = source;// 对拷贝对象进行赋值不会改变源对象的值copy = 234;// 同样对源对象赋值也不会改变拷贝对象的值source = 345;
浅拷贝：指的是拷贝一个对象时，仅仅拷贝对象的引用进行拷贝，但是拷贝对象和源对象还是引用同一份实体。此时，其中一个对象的改变都会影响到另一个对象。例如，一个人一开始叫张三，后来改名字为张老三了，可是他们还是同一个人，不管张三缺胳膊还是张老三少腿，都在同一个人身上。在.NET中引用类型就是一个例子。例如类的类型。具体例子如下所示：
public class Person{public string Name { get; set; }}class Program{static void Main(string[] args){Person sourceP = new Person() { Name = "张三" };Person copyP = sourceP; // 浅拷贝copyP.Name = "张老三"; // 拷贝对象改变Name值// 结果都是"张老三",因为实现的是浅拷贝，一个对象的改变都会影响到另一个对象Console.WriteLine("Person.Name: [SourceP: {0}] [CopyP:{1}]", sourceP.Name, copyP.Name);Console.Read();}}
三、深浅拷贝的几种实现方式
上面已经明白了深浅拷贝的定义，至于他们之间的区别也在定义中也有所体现。介绍完了它们的定义和区别之后，自然也就有了如何去实现它们呢？
对于，浅拷贝的实现方式很简单，.NET自身也提供了实现。我们知道，所有对象的父对象都是System.Object对象，这个父对象中有一个MemberwiseClone方法，该方法就可以用来实现浅拷贝，下面具体看看浅拷贝的实现方式，具体演示代码如下所示：
// 继承ICloneable接口，重新其Clone方法class ShallowCopyDemoClass : ICloneable{public int intValue = 1;public string strValue = "1";public PersonEnum pEnum = PersonEnum.EnumA;public PersonStruct pStruct = new PersonStruct() { StructValue = 1};public Person pClass = new Person("1");public int[] pIntArray = new int[] { 1 };public string[] pStringArray = new string[] { "1" };#region ICloneable成员public object Clone(){return this.MemberwiseClone();}#endregion}class Person{public string Name;public Person(string name){Name = name;}}public enum PersonEnum{EnumA = 0,EnumB = 1}public struct PersonStruct{public int StructValue;}
上面类中重写了IConeable接口的Clone方法，其实现直接调用了Object的MemberwiseClone方法来完成浅拷贝，如果想实现深拷贝，也可以在Clone方法中实现深拷贝的逻辑。接下来就是对上面定义的类进行浅拷贝测试了，看看是否是实现的浅拷贝，具体演示代码如下所示：
class Program{static void Main(string[] args){ShallowCopyDemo();// List浅拷贝的演示ListShallowCopyDemo();}public static void ListShallowCopyDemo(){List<PersonA> personList = new List<PersonA>(){new PersonA() { Name="PersonA", Age= 10, ClassA= new A() { TestProperty = "AProperty"} },new PersonA() { Name="PersonA2", Age= 20, ClassA= new A() { TestProperty = "AProperty2"} }};// 下面2种方式实现的都是浅拷贝List<PersonA> personsCopy = new List<PersonA>(personList);PersonA[] personCopy2 = new PersonA[2];personList.CopyTo(personCopy2);// 由于实现的是浅拷贝，所以改变一个对象的值，其他2个对象的值都会发生改变，因为它们都是使用的同一份实体，即它们指向内存中同一个地址personsCopy.First().ClassA.TestProperty = "AProperty3";WriteLog(string.Format("personCopy2.First().ClassA.TestProperty is {0}", personCopy2.First().ClassA.TestProperty));WriteLog(string.Format("personList.First().ClassA.TestProperty is {0}", personList.First().ClassA.TestProperty));WriteLog(string.Format("personsCopy.First().ClassA.TestProperty is {0}", personsCopy.First().ClassA.TestProperty));Console.Read();}public static void ShallowCopyDemo(){ShallowCopyDemoClass DemoA = new ShallowCopyDemoClass();ShallowCopyDemoClass DemoB = DemoA.Clone() as ShallowCopyDemoClass ;DemoB.intValue = 2;WriteLog(string.Format(" int->[A:{0}] [B:{1}]", DemoA.intValue, DemoB.intValue));DemoB.strValue = "2";WriteLog(string.Format(" string->[A:{0}] [B:{1}]", DemoA.strValue, DemoB.strValue));DemoB.pEnum = PersonEnum.EnumB;WriteLog(string.Format(" Enum->[A: {0}] [B:{1}]", DemoA.pEnum, DemoB.pEnum));DemoB.pStruct.StructValue = 2;WriteLog(string.Format(" struct->[A: {0}] [B: {1}]", DemoA.pStruct.StructValue, DemoB.pStruct.StructValue));DemoB.pIntArray[0] = 2;WriteLog(string.Format(" intArray->[A:{0}] [B:{1}]", DemoA.pIntArray[0], DemoB.pIntArray[0]));DemoB.pStringArray[0] = "2";WriteLog(string.Format("stringArray->[A:{0}] [B:{1}]", DemoA.pStringArray[0], DemoB.pStringArray[0]));DemoB.pClass.Name = "2";WriteLog(string.Format(" Class->[A:{0}] [B:{1}]", DemoA.pClass.Name, DemoB.pClass.Name));Console.WriteLine();}private static void WriteLog(string msg) { Console.WriteLine(msg); } } }
上面代码的运行结果如下图所示：
从上面运行结果可以看出，.NET中值类型默认是深拷贝的，而对于引用类型，默认实现的是浅拷贝。所以对于类中引用类型的属性改变时，其另一个对象也会发生改变。
上面已经介绍了浅拷贝的实现方式，那深拷贝要如何实现呢？在前言部分已经介绍了，实现深拷贝的方式有：反射、反序列化和表达式树。在这里，我只介绍反射和反序列化的方式，对于表达式树的方式在网上也没有找到，当时面试官说是可以的，如果大家找到了表达式树的实现方式，麻烦还请留言告知下。下面我们首先来看看反射的实现方式吧：
// 利用反射实现深拷贝public static T DeepCopyWithReflection<T>(T obj){Type type = obj.GetType();// 如果是字符串或值类型则直接返回if (obj is string || type.IsValueType) return obj;if (type.IsArray){Type elementType = Type.GetType(type.FullName.Replace("[]", string.Empty));var array = obj as Array;Array copied = Array.CreateInstance(elementType, array.Length);for (int i = 0; i < array.Length; i++){copied.SetValue(DeepCopyWithReflection(array.GetValue(i)), i);}return (T)Convert.ChangeType(copied, obj.GetType());}object retval = Activator.CreateInstance(obj.GetType());PropertyInfo[] properties = obj.GetType().GetProperties(BindingFlags.Public | BindingFlags.NonPublic| BindingFlags.Instance | BindingFlags.Static);foreach (var property in properties){var propertyValue = property.GetValue(obj, null);if (propertyValue == null)continue;property.SetValue(retval, DeepCopyWithReflection(propertyValue), null);}return (T)retval;}
反序列化的实现方式，反序列化的方式也可以细分为3种，具体的实现如下所示：
// 利用XML序列化和反序列化实现public static T DeepCopyWithXmlSerializer<T>(T obj){object retval;using (MemoryStream ms = new MemoryStream()){XmlSerializer xml = new XmlSerializer(typeof(T));xml.Serialize(ms, obj);ms.Seek(0, SeekOrigin.Begin);retval = xml.Deserialize(ms);ms.Close();}return (T)retval;}// 利用二进制序列化和反序列实现public static T DeepCopyWithBinarySerialize<T>(T obj){object retval;using (MemoryStream ms = new MemoryStream()){BinaryFormatter bf = new BinaryFormatter();// 序列化成流bf.Serialize(ms, obj);ms.Seek(0, SeekOrigin.Begin);// 反序列化成对象retval = bf.Deserialize(ms);ms.Close();}return (T)retval;}// 利用DataContractSerializer序列化和反序列化实现public static T DeepCopy<T>(T obj){object retval;using (MemoryStream ms = new MemoryStream()){DataContractSerializer ser = new DataContractSerializer(typeof(T));ser.WriteObject(ms, obj);ms.Seek(0, SeekOrigin.Begin);retval = ser.ReadObject(ms);ms.Close();}return (T)retval;}// 表达式树实现// ....
四、使用反射进行深拷贝如何解决相互引用的问题
上面反射的实现方式，对于相互引用的对象会出现StackOverflower的错误，由于对象的相互引用，会导致方法循环调用。下面就是一个相互引用对象的例子：
[Serializable]public class DeepCopyDemoClass{public string Name {get;set;}public int[] pIntArray { get; set; }public Address Address { get; set; }public DemoEnum DemoEnum { get; set; }// DeepCopyDemoClass中引用了TestB对象，TestB类又引用了DeepCopyDemoClass对象，从而造成了相互引用public TestB TestB {get;set;}public override string ToString(){return "DeepCopyDemoClass";}}[Serializable]public class TestB{public string Property1 { get; set; }public DeepCopyDemoClass DeepCopyClass { get; set; }public override string ToString(){return "TestB Class";}}[Serializable]public struct Address{public string City { get; set; }}public enum DemoEnum{EnumA = 0,EnumB = 1}
在面试过程中，针对这个问题的解决方式我回答的是不知道，回来之后思考了之后，也就有了点思路。首先想到的是：能不能用一个字典来记录每个对象被反射的次数，仔细想想可行，于是开始实现，初步修复后的反射实现如下所示：
public class DeepCopyHelper{// 用一个字典来存放每个对象的反射次数来避免反射代码的循环递归static Dictionary<Type, int> typereflectionCountDic = new Dictionary<Type, int>();public static T DeepCopyWithReflection_Second<T>(T obj){Type type = obj.GetType();// 如果是字符串或值类型则直接返回if (obj is string || type.IsValueType) return obj;if (type.IsArray){Type elementType = Type.GetType(type.FullName.Replace("[]", string.Empty));var array = obj as Array;Array copied = Array.CreateInstance(elementType, array.Length);for (int i = 0; i < array.Length; i++){copied.SetValue(DeepCopyWithReflection_Second(array.GetValue(i)), i);}return (T)Convert.ChangeType(copied, obj.GetType());}// 对于类类型开始记录对象反射的次数int reflectionCount = Add(typereflectionCountDic, obj.GetType());if (reflectionCount > 1)return obj; // 这里有错误object retval = Activator.CreateInstance(obj.GetType());PropertyInfo[] properties = obj.GetType().GetProperties(BindingFlags.Public | BindingFlags.NonPublic| BindingFlags.Instance | BindingFlags.Static);foreach (var property in properties){var propertyValue = property.GetValue(obj, null);if (propertyValue == null)continue;property.SetValue(retval, DeepCopyWithReflection_Second(propertyValue), null);}return (T)retval;}private static int Add(Dictionary<Type, int> dict, Type key){if (key.Equals(typeof(String)) || key.IsValueType) return 0;if (!dict.ContainsKey(key)){dict.Add(key, 1);return dict[key];}dict[key] += 1;return dict[key];}}
下面用代码来测试下上面的代码是否已经解决了循环递归的问题，具体的测试代码如下所示：
class Program{static void Main(string[] args){//ShallowCopyDemo();//ListShallowCopyDemo();DeepCopyDemo();DeepCopyDemo2();}private static void WriteLog(string msg){Console.WriteLine(msg);}public static void DeepCopyDemo(){DeepCopyDemoClass deepCopyClassA = new DeepCopyDemoClass();deepCopyClassA.Name = "DeepCopyClassDemo";deepCopyClassA.pIntArray = new int[] { 1 };deepCopyClassA.DemoEnum = DemoEnum.EnumA;deepCopyClassA.Address = new Address() { City = "Shanghai" };deepCopyClassA.TestB = new TestB() { Property1 = "TestProperty", DeepCopyClass = deepCopyClassA };// 使用反序列化来实现深拷贝DeepCopyDemoClass deepCopyClassB = DeepCopyHelper.DeepCopyWithBinarySerialize<DeepCopyDemoClass>(deepCopyClassA);deepCopyClassB.Name = "DeepCopyClassDemoB";WriteLog(string.Format(" Name->[A:{0}] [B:{1}]", deepCopyClassA.Name, deepCopyClassB.Name));deepCopyClassB.pIntArray[0] = 2;WriteLog(string.Format(" intArray->[A:{0}] [B:{1}]", deepCopyClassA.pIntArray[0], deepCopyClassB.pIntArray[0]));deepCopyClassB.Address = new Address() { City = "Beijing" };WriteLog(string.Format(" Addressstruct->[A: {0}] [B: {1}]", deepCopyClassA.Address.City, deepCopyClassB.Address.City));deepCopyClassB.DemoEnum = DemoEnum.EnumB;WriteLog(string.Format(" DemoEnum->[A: {0}] [B: {1}]", deepCopyClassA.DemoEnum, deepCopyClassB.DemoEnum));deepCopyClassB.TestB.Property1 = "TestPropertyB";WriteLog(string.Format(" Property1->[A:{0}] [B:{1}]", deepCopyClassA.TestB.Property1, deepCopyClassB.TestB.Property1));WriteLog(string.Format(" TestB.DeepCopyClass.Name->[A:{0}] [B:{1}]", deepCopyClassA.TestB.DeepCopyClass.Name, deepCopyClassB.TestB.DeepCopyClass.Name));Console.WriteLine();}public static void DeepCopyDemo2(){DeepCopyDemoClass deepCopyClassA = new DeepCopyDemoClass();deepCopyClassA.Name = "DeepCopyClassDemo";deepCopyClassA.pIntArray = new int[] { 1, 2 };deepCopyClassA.DemoEnum = DemoEnum.EnumA;deepCopyClassA.Address = new Address() { City = "Shanghai" };deepCopyClassA.TestB = new TestB() { Property1 = "TestProperty", DeepCopyClass = deepCopyClassA };// 使用反射来完成深拷贝DeepCopyDemoClass deepCopyClassB = DeepCopyHelper.DeepCopyWithReflection_Second<DeepCopyDemoClass>(deepCopyClassA);//DeepCopyDemoClass deepCopyClassB = DeepCopyHelper.DeepCopyWithReflection<DeepCopyDemoClass>(deepCopyClassA);deepCopyClassB.Name = "DeepCopyClassDemoB";WriteLog(string.Format(" Name->[A:{0}] [B:{1}]", deepCopyClassA.Name, deepCopyClassB.Name));deepCopyClassB.pIntArray[0] = 2;WriteLog(string.Format(" intArray->[A:{0}] [B:{1}]", deepCopyClassA.pIntArray[0], deepCopyClassB.pIntArray[0]));deepCopyClassB.Address = new Address() { City = "Beijing" };WriteLog(string.Format(" Addressstruct->[A: {0}] [B: {1}]", deepCopyClassA.Address.City, deepCopyClassB.Address.City));deepCopyClassB.DemoEnum = DemoEnum.EnumB;WriteLog(string.Format(" DemoEnum->[A: {0}] [B: {1}]", deepCopyClassA.DemoEnum, deepCopyClassB.DemoEnum));deepCopyClassB.TestB.Property1 = "TestPropertyB";WriteLog(string.Format(" Property1->[A:{0}] [B:{1}]", deepCopyClassA.TestB.Property1, deepCopyClassB.TestB.Property1));WriteLog(string.Format(" TestB.DeepCopyClass.Name->[A:{0}] [B:{1}]", deepCopyClassA.TestB.DeepCopyClass.Name, deepCopyClassB.TestB.DeepCopyClass.Name));Console.ReadKey();}}
此时的运行结果如下图所示：
刚开始看到这样的运行结果，开心地以为已经解决了循环递归的问题了，因为此时结果成功运行出来了，没有了StackOverflower的错误了。但是仔细一看，反序列化和反射完成的深拷贝的运行结果不一样，如上图中红色圈出来的部分。显然，反序列化的结果是没有错误的，显然目前实现的反射代码还是有问题的。接下来就是思考了。为什么上面反射的代码不正确呢？
仔细分析DeepCopyWithReflection_Second中的代码，发现下面代码红色部分是错误的：
int reflectionCount = Add(typereflectionCountDic, obj.GetType());if (reflectionCount > 1)return obj; // 是错误的
对DeepCopyWithReflection_Second方法仔细分析，在对TestB进行反射时，当反射到DeepCopyClass属性时，此时会递归调用DeepCopyWithReflection_Second方法，此时在typereflectionCountDic发现DeepCopyDemoClass已经被反射了，则直接返回，这样分析好像没什么错误，但是此时返回的是deepCopyClassA对象，但是我们需要返回的是deepCopyClassB对象，即此时deepCopyClassB对象的内存结构如下图所示：
而我们其实需要deepCopyClassB对象的内存结构如下图所示：
既然找到了DeepCopyWithReflection_Second的错误原因，那我们就要解决了。上面说我们返回的应该是deepCopyClassB对象，而我们怎么得到创建的deepCopyClassB对象呢？这里我就想能不能用一个变量来保存一开始通过CreateInstance方法创建的deepCopyClassB对象呢？验证想法最好的办法就是代码了，这样我就按照这个思路对DeepCopyWithReflection_Second又进行一次改进，最终的代码如下所示：
public static T DeepCopyWithReflection_Third<T>(T obj){Type type = obj.GetType();// 如果是字符串或值类型则直接返回if (obj is string || type.IsValueType) return obj;if (type.IsArray){Type elementType = Type.GetType(type.FullName.Replace("[]", string.Empty));var array = obj as Array;Array copied = Array.CreateInstance(elementType, array.Length);for (int i = 0; i < array.Length; i++){copied.SetValue(DeepCopyWithReflection_Second(array.GetValue(i)), i);}return (T)Convert.ChangeType(copied, obj.GetType());}int reflectionCount = Add(typereflectionCountDic, obj.GetType());if (reflectionCount > 1 && obj.GetType() == typeof(DeepCopyDemoClass))return (T)DeepCopyDemoClasstypeRef; // 返回deepCopyClassB对象object retval = Activator.CreateInstance(obj.GetType());if(retval.GetType() == typeof(DeepCopyDemoClass))DeepCopyDemoClasstypeRef = retval; // 保存一开始创建的DeepCopyDemoClass对象PropertyInfo[] properties = obj.GetType().GetProperties(BindingFlags.Public | BindingFlags.NonPublic| BindingFlags.Instance | BindingFlags.Static);foreach (var property in properties){var propertyValue = property.GetValue(obj, null);if (propertyValue == null)continue;property.SetValue(retval, DeepCopyWithReflection_Third(propertyValue), null);}return (T)retval;}
下面我用DeepCopyWithReflection_Third方法来测试下，具体的测试代码如下所示：
class Program{static void Main(string[] args){//ShallowCopyDemo();//ListShallowCopyDemo();DeepCopyDemo();DeepCopyDemo2();}private static void WriteLog(string msg){Console.WriteLine(msg);}public static void DeepCopyDemo(){DeepCopyDemoClass deepCopyClassA = new DeepCopyDemoClass();deepCopyClassA.Name = "DeepCopyClassDemo";deepCopyClassA.pIntArray = new int[] { 1 };deepCopyClassA.DemoEnum = DemoEnum.EnumA;deepCopyClassA.Address = new Address() { City = "Shanghai" };deepCopyClassA.TestB = new TestB() { Property1 = "TestProperty", DeepCopyClass = deepCopyClassA };// 使用反序列化来实现深拷贝DeepCopyDemoClass deepCopyClassB = DeepCopyHelper.DeepCopyWithBinarySerialize<DeepCopyDemoClass>(deepCopyClassA);deepCopyClassB.Name = "DeepCopyClassDemoB";WriteLog(string.Format(" Name->[A:{0}] [B:{1}]", deepCopyClassA.Name, deepCopyClassB.Name));deepCopyClassB.pIntArray[0] = 2;WriteLog(string.Format(" intArray->[A:{0}] [B:{1}]", deepCopyClassA.pIntArray[0], deepCopyClassB.pIntArray[0]));deepCopyClassB.Address = new Address() { City = "Beijing" };WriteLog(string.Format(" Addressstruct->[A: {0}] [B: {1}]", deepCopyClassA.Address.City, deepCopyClassB.Address.City));deepCopyClassB.DemoEnum = DemoEnum.EnumB;WriteLog(string.Format(" DemoEnum->[A: {0}] [B: {1}]", deepCopyClassA.DemoEnum, deepCopyClassB.DemoEnum));deepCopyClassB.TestB.Property1 = "TestPropertyB";WriteLog(string.Format(" Property1->[A:{0}] [B:{1}]", deepCopyClassA.TestB.Property1, deepCopyClassB.TestB.Property1));WriteLog(string.Format(" TestB.DeepCopyClass.Name->[A:{0}] [B:{1}]", deepCopyClassA.TestB.DeepCopyClass.Name, deepCopyClassB.TestB.DeepCopyClass.Name));Console.WriteLine();}public static void DeepCopyDemo2(){DeepCopyDemoClass deepCopyClassA = new DeepCopyDemoClass();deepCopyClassA.Name = "DeepCopyClassDemo";deepCopyClassA.pIntArray = new int[] { 1, 2 };deepCopyClassA.DemoEnum = DemoEnum.EnumA;deepCopyClassA.Address = new Address() { City = "Shanghai" };deepCopyClassA.TestB = new TestB() { Property1 = "TestProperty", DeepCopyClass = deepCopyClassA };// 使用反射来完成深拷贝DeepCopyDemoClass deepCopyClassB = DeepCopyHelper.DeepCopyWithReflection_Third<DeepCopyDemoClass>(deepCopyClassA);//DeepCopyDemoClass deepCopyClassB = DeepCopyHelper.DeepCopyWithReflection<DeepCopyDemoClass>(deepCopyClassA);deepCopyClassB.Name = "DeepCopyClassDemoB";WriteLog(string.Format(" Name->[A:{0}] [B:{1}]", deepCopyClassA.Name, deepCopyClassB.Name));deepCopyClassB.pIntArray[0] = 2;WriteLog(string.Format(" intArray->[A:{0}] [B:{1}]", deepCopyClassA.pIntArray[0], deepCopyClassB.pIntArray[0]));deepCopyClassB.Address = new Address() { City = "Beijing" };WriteLog(string.Format(" Addressstruct->[A: {0}] [B: {1}]", deepCopyClassA.Address.City, deepCopyClassB.Address.City));deepCopyClassB.DemoEnum = DemoEnum.EnumB;WriteLog(string.Format(" DemoEnum->[A: {0}] [B: {1}]", deepCopyClassA.DemoEnum, deepCopyClassB.DemoEnum));deepCopyClassB.TestB.Property1 = "TestPropertyB";WriteLog(string.Format(" Property1->[A:{0}] [B:{1}]", deepCopyClassA.TestB.Property1, deepCopyClassB.TestB.Property1));WriteLog(string.Format(" TestB.DeepCopyClass.Name->[A:{0}] [B:{1}]", deepCopyClassA.TestB.DeepCopyClass.Name, deepCopyClassB.TestB.DeepCopyClass.Name));Console.ReadKey();}}
此时的运行结果如下图示所示：
从上面的测试结果可以看出，此时深拷贝的反射实现方法基本上没什么问题了。这个方法也同时解决了相互引用对象的循环递归问题。
五、总结
到这里，该文章的内容就结束。这里主要记录下自己在一次面试过程中遇到问题的一次总结，从中可以看出，反射进行深拷贝会有很多其他的问题，所以平时还是建议大家使用序列化的形式来进行深拷贝。
最后附上本文所有源码下载：DeepCopy.zip
