Remoting中数据序列化

该文讲述通过网络传输序列化数据的两个类，BinaryFormatter和SoapFormatter类。这些类可以将类的实例转化成字节流通过网络传输到远程系统，也可以转换回原来的数据。

一、 使用序列化类

序列化一个类，并通过网络传输需要三步：

1、将要序列化的类创建成一个library对象。

2、编写一个发送程序来创建要序列化类的实例，并发送。

3、编写一个接收程序从流中读取数据，并重新创建原来的序列化类。

① 编写要序列化的类

每个要通过网络传输数据的类必须在原代码文件里使用[Serializable]标签。这表明，类中所有的数据在传输时都将要被序列化。下面展示了如何创建一个可以序列化的类。

using System;
[Serializable]
public class SerialEmployee
{
public int EmployeeID
public string LastName;
public string FirstName;
public int YearsService;
public double Salary;
public SerialEmployee()
{
EmployeeID = 0;
LastName = null;
FirstName = null;
YearsService = 0;
Salary = 0.0;
}
}
为了使用该类来传输数据，必须现创建一个library文件：

csc /t:library SerialEmployee.cs

② 编写一个传输程序

创建数据类以后，可以创建一个程序来传输数据。可以使用BinaryFormatter和SoapFormatter类来序列化数据。

BinaryFormatter将数据序列化为二进制流。通常在实际数据中，增加一些信息，例如类名和版本号信息。

也可以使用SoapFormatter类使用XML格式来传输数据。使用XML的好处就是可以在任何系统和程序间传递数据。

第一必须创建一个流的实例来传递数据。可以是任何类型的流，包括FileStream，MemoryStream，NetworkStream。然后，可以创建一个序列化类，使用Serialize()方法来通过流对象传递数据：

Stream str = new FileStream( "testfile.bin", FileMode.Create, FileAccess.ReadWrite);
IFormatter formatter = new BinaryFormatter();
formatter.Serialize(str, data);

Iformatter类创建了一个用来序列化的类的实例(BinaryFormatter或者SoapFormatter)，使用Serialize()类来将数据序列化

using System;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Soap;
class SoapTest
{
public static void Main()
{
SerialEmployee emp1 = new SerialEmployee();
SerialEmployee emp2 = new SerialEmployee();
emp1.EmployeeID = 1;
emp1.LastName = "Blum";
emp1.FirstName = "Katie Jane";
emp1.YearsService = 12;
emp1.Salary = 35000.50;
emp2.EmployeeID = 2;
emp2.LastName = "Blum";
emp2.FirstName = "Jessica";
emp2.YearsService = 9;
emp2.Salary = 23700.30;
Stream str = new FileStream("soaptest.xml", FileMode.Create,
FileAccess.ReadWrite);
IFormatter formatter = new SoapFormatter();
formatter.Serialize(str, emp1);
formatter.Serialize(str, emp2);
str.Close();
}
}
SoapFormatter类包含在System.Runtime.Serialization.Formatters.Soap命名空间，BinaryFormatter类包含在System.Runtime.Serialization.Formatters.Binary命名空间，Iformatter接口包含在System.Runtime.Serialization命名空间。

编译代码：CSC /r:SerialEmployee.dll SoapTest.cs

运行SoapTest.exe程序后，可以查看产生的soaptest.xml文件

<SOAP-ENV:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" Â
xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:SOAP-ENC= Â
"http://schemas.xmlsoap.org/soap/encoding/" xmlns:SOAP-ENV= Â
"http://schemas.xmlsoap.org/soap/envelope/" xmlns:clr= Â
"http://schemas.microsoft.com/soap/encoding/clr/1.0" SOAP-ENV:encodingStyle= Â
"http://schemas.xmlsoap.org/soap/encoding/">
<SOAP-ENV:Body>
<a1:SerialEmployee xmlns:a1= Â
"http://schemas.microsoft.com/clr/assem/SerialEmployee%2C%20Version%3D0.Â
0.0.0%2C%20Culture%3Dneutral%2C%20PublicKeyToken%3Dnull">
<EmployeeID>1</EmployeeID>
<LastName>Blum</LastName>
<FirstName>Katie Jane</FirstName>
<YearsService>12</YearsService>
<Salary>35000.5</Salary>
</a1:SerialEmployee>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>
<SOAP-ENV:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" Â
xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:SOAP-ENC= Â
"http://schemas.xmlsoap.org/soap/encoding/" xmlns:SOAP-ENV= Â
"http://schemas.xmlsoap.org/soap/envelope/" xmlns:clr= Â
"http://schemas.microsoft.com/soap/encoding/clr/1.0" SOAP-ENV:encodingStyle= Â
"http://schemas.xmlsoap.org/soap/encoding/">
<SOAP-ENV:Body>
<a1:SerialEmployee xmlns:a1= Â
"http://schemas.microsoft.com/clr/assem/SerialEmployee%2C%20Version%3D0.Â
0.0.0%2C%20Culture%3Dneutral%2C%20PublicKeyToken%3Dnull">
<EmployeeID>2</EmployeeID>
<LastName>Blum</LastName>
<FirstName>Jessica</FirstName>
<YearsService>9</YearsService>
<Salary>23700.3</Salary>
</a1:SerialEmployee>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>
查看soaptest.xml文件，我们可以发现在序列化类中SOAP是如何定义每个数据元素。一个值得注意的重要XML数据特点如下：

<a1:SerialEmployee xmlns:a1= Â
"http://schemas.microsoft.com/clr/assem/SerialEmployee%2C%20Version%3D0.Â0.0.0.%2C%20Culture%3Dneutral%2C%20PublicKeyToken%3Dnull">
这里，XML中定义的数据使用了序列化数据类的实际类名。如果接收程序使用了另一个不同的类名，会和从流中读取的XML数据不匹配。类不匹配，读取将会失败。

下面的代码展示了如何序列化数据，将数据传送到远程系统。

using System;
using System.Net;
using System.Net.Sockets;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
class BinaryDataSender
{
public static void Main()
{
SerialEmployee emp1 = new SerialEmployee();
SerialEmployee emp2 = new SerialEmployee();
emp1.EmployeeID = 1;
emp1.LastName = "Blum";
emp1.FirstName = "Katie Jane";
emp1.YearsService = 12;
emp1.Salary = 35000.50;
emp2.EmployeeID = 2;
emp2.LastName = "Blum";
emp2.FirstName = "Jessica";
emp2.YearsService = 9;
emp2.Salary = 23700.30;
TcpClient client = new TcpClient("127.0.0.1", 9050);
IFormatter formatter = new BinaryFormatter();
NetworkStream strm = client.GetStream();
formatter.Serialize(strm, emp1);
formatter.Serialize(strm, emp2);
strm.Close();
client.Close();
}
}
因为BinaryFormatter和SoapFormatter类需要一个Stream对象来传递序列化的数据，所以要使用一个TCP Socket对象或者一个TcpClient对象来传递数据，不能直接使用UDP。

③编写一个接收程序

using System;
using System.Net;
using System.Net.Sockets;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
class BinaryDataRcvr
{
public static void Main()
{
TcpListener server = new TcpListener(9050);
server.Start();
TcpClient client = server.AcceptTcpClient();
NetworkStream strm = client.GetStream();
IFormatter formatter = new BinaryFormatter();
SerialEmployee emp1 = (SerialEmployee)formatter.Deserialize(strm);
Console.WriteLine("emp1.EmployeeID = {0}", emp1.EmployeeID);
Console.WriteLine("emp1.LastName = {0}", emp1.LastName);
Console.WriteLine("emp1.FirstName = {0}", emp1.FirstName);
Console.WriteLine("emp1.YearsService = {0}", emp1.YearsService);
Console.WriteLine("emp1.Salary = {0}\n", emp1.Salary);
SerialEmployee emp2 = (SerialEmployee)formatter.Deserialize(strm);
Console.WriteLine("emp2.EmployeeID = {0}", emp2.EmployeeID);
Console.WriteLine("emp2.LastName = {0}", emp2.LastName);
Console.WriteLine("emp2.FirstName = {0}", emp2.FirstName);
Console.WriteLine("emp2.YearsService = {0}", emp2.YearsService);
Console.WriteLine("emp2.Salary = {0}", emp2.Salary);
strm.Close();
server.Stop();
}
}

二、 程序改进

在前面的程序中有一个假设：发送者的所有数据都被接收者接收。如果数据丢失，调用Deserialize()方法会发生错误。一个简单的解决方法是将序列化数据放到MemoryStream对象中。MemoryStream对象将所有的序列化数据保存在内存中，可以很容易得到序列化数据的大小。当传递数据时，将数据大小和数据一起传递。

using System;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Soap;
class BetterDataSender
{
public void SendData (NetworkStream strm, SerialEmployee emp)
{
IFormatter formatter = new SoapFormatter();
MemoryStream memstrm = new MemoryStream();
formatter.Serialize(memstrm, emp);
byte[] data = memstrm.GetBuffer();
int memsize = (int)memstrm.Length;
byte[] size = BitConverter.GetBytes(memsize);
strm.Write(size, 0, 4);
strm.Write(data, 0, memsize);
strm.Flush();
memstrm.Close();
}
public BetterDataSender()
{
SerialEmployee emp1 = new SerialEmployee();
SerialEmployee emp2 = new SerialEmployee();
emp1.EmployeeID = 1;
emp1.LastName = "Blum";
emp1.FirstName = "Katie Jane";
emp1.YearsService = 12;
emp1.Salary = 35000.50;
emp2.EmployeeID = 2;
emp2.LastName = "Blum";
emp2.FirstName = "Jessica";
emp2.YearsService = 9;
emp2.Salary = 23700.30;
TcpClient client = new TcpClient("127.0.0.1", 9050);
NetworkStream strm = client.GetStream();
SendData(strm, emp1);
SendData(strm, emp2);
strm.Close();
client.Close();
}
public static void Main()
{
BetterDataSender bds = new BetterDataSender();
}
}
接收数据程序如下：

using System;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Soap;
class BetterDataRcvr
{
private SerialEmployee RecvData (NetworkStream strm)
{
MemoryStream memstrm = new MemoryStream();
byte[] data = new byte[4];
int recv = strm.Read(data, 0, 4);
int size = BitConverter.ToInt32(data, 0);
int offset = 0;
while(size > 0)
{
data = new byte[1024];
recv = strm.Read(data, 0, size);
memstrm.Write(data, offset, recv);
offset += recv;
size -= recv;
}
IFormatter formatter = new SoapFormatter();
memstrm.Position = 0;
SerialEmployee emp = (SerialEmployee)formatter.Deserialize(memstrm);
memstrm.Close();
return emp;
}
public BetterDataRcvr()
{
TcpListener server = new TcpListener(9050);
server.Start();
TcpClient client = server.AcceptTcpClient();
NetworkStream strm = client.GetStream();
SerialEmployee emp1 = RecvData(strm);
Console.WriteLine("emp1.EmployeeID = {0}", emp1.EmployeeID);
Console.WriteLine("emp1.LastName = {0}", emp1.LastName);
Console.WriteLine("emp1.FirstName = {0}", emp1.FirstName);
Console.WriteLine("emp1.YearsService = {0}", emp1.YearsService);
Console.WriteLine("emp1.Salary = {0}\n", emp1.Salary);
SerialEmployee emp2 = RecvData(strm);
Console.WriteLine("emp2.EmployeeID = {0}", emp2.EmployeeID);
Console.WriteLine("emp2.LastName = {0}", emp2.LastName);
Console.WriteLine("emp2.FirstName = {0}", emp2.FirstName);
Console.WriteLine("emp2.YearsService = {0}", emp2.YearsService);
Console.WriteLine("emp2.Salary = {0}", emp2.Salary);
strm.Close();
server.Stop();
}
public static void Main()
{
BetterDataRcvr bdr = new BetterDataRcvr();
}
}