Tài liệu Module 12: Serialization docx

Contents Overview 1 Serialization Scenarios 2 Serialization Attributes 4 Object Graph 5 Serialization Process 7 Serialization Example 9 Deserialization Example 10 Custom Serialization 12 Custom Serialization Example 14 Security Issues 17 Lab 12: Serialization 18 Review 27 Module 12: Serialization Information in this document, including URL and other Internet Web site references, is subject to change without notice. Unless otherwise noted, the example companies, organizations, products, domain names, e-mail addresses, logos, people, places and events depicted herein are fictitious, and no association with any real company, organization, product, domain name, e-mail address, logo, person, place or event is intended or should be inferred. Complying with all applicable copyright laws is the responsibility of the user. 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Microsoft, ActiveX, BizTalk, IntelliMirror, Jscript, MSDN, MS-DOS, MSN, PowerPoint, Visual Basic, Visual C++, Visual C#, Visual Studio, Win32, Windows, Windows Media, and Window NT are either registered trademarks or trademarks of Microsoft Corporation in the U.S.A. and/or other countries. The names of actual companies and products mentioned herein may be the trademarks of their respective owners. Module 12: Serialization iii Instructor Notes After completing this module, students will be able to: • Write an application that serializes and deserializes an object graph by using either a binary or Simple Object Access Protocol (SOAP) XML format. Materials and Preparation This section provides the materials and preparation tasks that you need to teach this module. Required Materials To teach this module, you need the Microsoft ® PowerPoint ® file 2349B_12.ppt. Preparation Tasks To prepare for this module, you should: ! Read all of the materials for this module. ! Complete the lab. Presentation: 30 Minutes Lab: 45 Minutes iv Module 12: Serialization Module Strategy Use the following strategy to present this module: ! Serialization Scenarios Discuss briefly how serialization is used in scenarios such as persisting in- memory objects to disk and in remoting. Mention the Microsoft .NET Framework’s support for serialization and deserialization as an introduction to the rest of the module. ! Serialization Attributes Explain how to mark a class with serialization attributes in C# by using the Serializable attribute. Also cover the NonSerialized attribute. ! Object Graph Use the diagram on the Object Graph slide to discuss the object graph concept and the algorithm that is used to serialize or deserialize an object graph. ! Serialization Process Introduce the classes that are used in the serialization process. ! Serialization Example Discuss the code example on the Serialization Example slide in which default serialization is performed on a graph of objects, whose root is an ArrayList, and the serialized stream is written to a FileStream in binary format. ! Deserialization Example Use the preceding serialization example to show how to create a clone of the graph by deserializing it. ! Custom Serialization Discuss when to use custom serialization and the implementation details of using the ISerializable interface to perform custom serialization and deserialization. ! Custom Serialization Example Show how to provide custom serialization for a class named ISerializableExample. ! Security Issues Because the serialization engine handles both the public and private state of the objects that are passed to it, emphasize that streams with private data should be treated carefully, and that some form of encryption should be used for sensitive data, before that data is transmitted over the wire or persisted to disk. Module 12: Serialization 1 Overview ! Serialization Scenarios ! Serialization Attributes ! Object Graph ! Serialization Process ! Serialization Example ! Deserialization Example ! Custom Serialization ! Custom Serialization Example ! Security Issues ***************************** ILLEGAL FOR NON - TRAINER USE ****************************** Serialization is the process of converting a graph of objects into a linear sequence of bytes. That sequence of bytes can be sent elsewhere, for example, to a remote computer, and be deserialized, thereby making a clone in the remote memory of the original graph of objects. After completing this module, you will be able to: • Write an application that serializes and deserializes an object graph by using either a binary or Simple Object Access Protocol (SOAP) XML format. Topic Objective To provide an overview of the module topics and objectives. Lead-in In this module, you will learn about serialization and learn how to write an application that serializes and deserializes an object graph by using a binary or SOAP XML format. 2 Module 12: Serialization Serialization Scenarios ! Persistence " Store and retrieve a graph of objects to and from a file ! Remoting " Pass by value arguments that are transmitted between processes ***************************** ILLEGAL FOR NON - TRAINER USE ****************************** Serialization is used in some very common scenarios, such as persisting a graph of objects to disk or to objects in another process. The Microsoft ® .NET Framework provides support for serialization and deserialization. Persistence Consider a simple single-user desktop application, such as a two-dimensional drafting package that is built by using object-oriented techniques. In such an application, a drawing is composed of different kinds of graphical objects of various types. The application represents the drawing as a graph of in-memory objects. One object represents the root of the entire picture. For example, a simple round table could be represented by a graph that consists of a root object that is an instance of a circle class. This instance of the circle class has four children that are each instances of a line class. To save the entire drawing to a disk file so the drawing can be restored after rebooting the computer, you could force each class to implement a serialize and corresponding deserialize method. However, this approach is a potentially burdensome task for the application programmer. Serialization in the .NET Framework The .NET Framework common language runtime reduces the amount of work that is involved in serialization. At run time, the common language runtime maintains metadata that allows serialization code to discover the types and values of all fields and properties that make up any object. Using the common language runtime, an application requires only a few lines of code to serialize a object, such as the drawing described in the preceding paragraphs, and write it to a file, or to deserialize such a file into an in-memory graph of objects. Topic Objective To show how serialization is used. Lead-in Serialization is used in some very common scenarios, such as persisting a graph of objects to disk or to objects in another process. Module 12: Serialization 3 Remoting In distributed computing, objects in one process may need to communicate with objects in another process. In the .NET Framework, the term remoting is typically used to refer to the process in which an object invokes a method in another object that is not in the same application domain. If the remote method takes as one of its arguments an object that lies at the root of a graph of objects, and if all of the objects in the graph are marked as remote-by-value, you must serialize a copy of the object graph and pass the graph to the remote object. The remote object must then deserialize the argument into an in-memory graph of objects. For more information about remoting, see Module 13, “Remoting and Web Services,” in Course 2349B, Programming with the Microsoft .NET Framework (Microsoft Visual C# .NET). 4 Module 12: Serialization Serialization Attributes ! To Mark a Class, Use Serializable Attribute ! To Skip Specified Members, Use NonSerialized Attribute ! To Provide Custom Serialization, Implement ISerializable [Serializable] public class MyClass {} [Serializable] public class MyClass {} [Serializable] public class MyClass { [NonSerialized] int _cashSize; // } [Serializable] public class MyClass { [NonSerialized] int _cashSize; // } ***************************** ILLEGAL FOR NON - TRAINER USE ****************************** If you are writing a class, you should be aware of serialization. The common language runtime’s serialization services are built with the assumption that a type is not serializable unless the type is specifically marked as serializable. In the simplest case, all you need to do is mark a class as serializable because the runtime metadata understands everything about each object’s layout in memory, and its field and property definitions. To mark a type as serializable in C#, you use the Serializable attribute, which is a reserved custom attribute. All fields in classes with this attribute are serialized, even private fields. In the following example, MyClass is marked as serializable: [Serializable] public class MyClass {} For slightly more complex classes that have state that is invalid to serialize, the runtime provides support for marking those fields and properties as transient. For example, the following code uses the NonSerialized attribute to ensure that the _cashSize member of MyClass is not serialized: [Serializable] public class MyClass { [NonSerialized] int _cashSize; // } The small set of classes that need to participate in their own serialization and deserialization can provide a custom implementation of the ISerializable interface. For more information about custom serialization, see Custom Serialization in this module. Topic Objective To explain how to mark a class with serialization attributes in C#. Lead-in If you are writing a class, you should be aware of serialization. Module 12: Serialization 5 Object Graph Dog Cat Duck Mouse Horse Duck 3 3 7 7 4 4 2 2 9 9 1 1 ***************************** ILLEGAL FOR NON - TRAINER USE ****************************** An object graph is a set of objects with references to each other. Serialization must provide a way to represent the links between the graph’s objects in the serialized stream that is created in the serialization process. Understanding Object Graphs Serialization of an object graph must provide a way to represent the links between the graph’s objects in the serialized stream that it creates. The value that is held in the field of the in-memory object, which links to another object, is essentially a 32-bit address. This address has meaning only in the owner address space and may change during garbage collection. Therefore, serialization must allocate a unique number to each object in the stream. The illustration in the slide shows a graph of animal objects. Each object is represented as a box with its identification number inside the box and its class name to the right of the box. You can represent the graph of objects that is shown in this illustration with a serialized stream, as in the following example: Dog, 3, ref4, ref7, ref1 || Cat, 4, ref9 || Duck, 7 || Mouse, 1, ref9, ref2 || Horse, 9, ref4 || Duck, 2 The order in which you stream out the objects does not matter, nor does it matter what numbers you assign to the objects. What does matter is that no two objects are assigned the same number. The object numbers are significant only within a serialized stream. They are simply a way to represent the graph topology and to allow you to reconstruct a copy of that graph, perhaps on another computer. Topic Objective To define an object graph and explain its function. Lead-in An object graph is a set of objects that share a set of references to each other. 6 Module 12: Serialization Tracking Object References An algorithm that visits objects one at a time clearly must keep track of which objects it has already visited, for example, by using an internal list. Without due care, the algorithm may incorrectly serialize or deserialize an object graph. For example, in the object graph in the illustration, to avoid entering an infinite loop, you must detect the cycle in the graph that occurs because of the mutual references between Cat 4 and Horse 9. During serialization, you must note that the Cat 4 that is linked to by Dog 3 is the same Cat 4 that is linked to by Horse 9 to ensure that deserialization will result in both Dog 3 and Horse 9 referring to the same Cat 4 object and not to two different copies. [...]... 6 26 Module 12: Serialization 8 Using Visual Studio NET, open and visually examine the Array.soap file in the bin\Debug subdirectory, and note the serialized array data’s format, structure, and size Module 12: Serialization 27 Review Topic Objective To reinforce module objectives by reviewing key points ! Serialization Attributes ! Object Graph ! Serialization Process ! Serialization Example Deserialization... and add any additional fields that are required for serializing the derived class to the returned SerializationInfo Module 12: Serialization 13 Deserialization Deserialization occurs during the call to the class’s constructor If you need to create custom deserialization of an object, you use the object’s SerializationInfo, which has been populated with the type of the object and the name/object pairs... cache the SerializationInfo and then implement IDeserializationCallback 14 Module 12: Serialization Custom Serialization Example [Serializable] public class ExampleFoo : ISerializable [Serializable] public class ExampleFoo : ISerializable { { public int i, j, k; public int i, j, k; public ExampleFoo() {} public ExampleFoo() {} internal ExampleFoo(SerializationInfo si, internal ExampleFoo(SerializationInfo... following page.) Module 12: Serialization public static void PrintValues( IEnumerable myList ) { System.Collections.IEnumerator myEnumerator = myList.GetEnumerator(); while ( myEnumerator.MoveNext() ) Console.WriteLine( "{0}", myEnumerator.Current ); } } 11 12 Module 12: Serialization Custom Serialization Topic Objective To explain what is required to implement ISerializable for performing custom serialization. .. complete this lab: 45 minutes Module 12: Serialization 19 Exercise 1 Creating the Basic Serialization Application In this exercise, you will modify the Serialization application to provide methods to serialize and deserialize a linked list ! To create the basic Serialization application in binary format 1 In the \Labs\Lab12\Starter directory, open the Serialization project in Visual... some form of encryption 18 Module 12: Serialization Lab 12: Serialization Topic Objective To introduce the lab Lead-in In this lab, you will write a client/server application that uses serialization *****************************ILLEGAL FOR NON-TRAINER USE****************************** Objectives After completing this lab, you will be able to: • Create an application that uses serialization as it is implemented... b = new BinaryFormatter(); // serialize the graph to the stream b.Serialize(s, l); s.Close(); } } 10 Module 12: Serialization Deserialization Example Topic Objective To show how to create a clone of the graph by deserializing it Lead-in The preceding Serialization Example shows how to perform default serialization of a graph of objects, whose root is an ArrayList, with a serialized stream that is written... int i, j, k; public ExampleFoo() { } internal ExampleFoo(SerializationInfo si, StreamingContext context) { //Restore our scalar values i = si.GetInt32("i"); j = si.GetInt32("j"); k = si.GetInt32("k"); } (Code continued on the following page.) 16 Module 12: Serialization public void GetObjectData(SerializationInfo si, StreamingContext context) { //SerializationInfo is essentially a property bag //Add our.. .Module 12: Serialization 7 Serialization Process Topic Objective ! To introduce the classes that are used in the serialization process Classes Used by the Default Serialization Process " " Lead-in The process of serializing an object graph involves identifying the individual objects... interface, you implement the GetObjectData method on your object and add a constructor that takes a SerializationInfo and a StreamingContext, as shown in Custom Serialization Example in this module When GetObjectData is called during serialization, you are responsible for populating a SerializationInfo object A SerializationInfo object is a PropertyBag that contains the type of the object that is being serialized . Example 10 Custom Serialization 12 Custom Serialization Example 14 Security Issues 17 Lab 12: Serialization 18 Review 27 Module 12: Serialization . disk. Module 12: Serialization 1 Overview ! Serialization Scenarios ! Serialization Attributes ! Object Graph ! Serialization Process ! Serialization