The development of three basic concepts: Chinese Forum Network collection Source: http: //www.51one.net Add Time: 2004-8-25 three-tier client / server
One: Advantages: flexibility and scalability. Application of three-story development technology (distributed)
(Reference Bibliography: Delphi 5.x Distributed Multi-Layer Application System) 1: Solve the maintenance cost problem of client / server structure, improve client / server structural ductility issues. The number of users supported by the client / server structure has a certain limit (less than 200 people). The structure limits the development of Internet / Intranet and e-commerce. Three-layer development application Database Pooling, Object Pooling, Resource Pool, thread mode provides high ductility. Two: Solve the problem of application logic reuse. For example, when enterprises want to add a web browsing service on the original client / server structure, you need to configure the web server, rewrite all application logic, and update the MIS system. In the three-layer structure, use COM / DCOM, CORBA (Common Object Request Broker Architecture), or Enterprise Java Bean, etc., packaged company's logic code (called corporate object), can solve the above problems. It greatly reduces the cost of development and maintenance. Three: Integrate the needs of different system structures, and apply new technologies in time. 2: 3-layer service model of Microsoft 1: Structure: It is a tool for Windows DNA (Distributed Internet Applications, Distributed Internal Network) COM (Component Object Model, Component Object Model) Components as tools for implementing system and application services. l User Services L Business Services L Data Service (1) User Service: Windows DNA defines four customers that can be used to implement user service layer: N standard Browse customers: Depending on simple, page-based HTML to manage data representations and users Interaction. Its compatibility is very good and the function is not rich. N Enhanced Browser Customer: Draw a special browser (EX: Dynamic HTML, script, and ActiveX control) to maximize the richness and function of the user interface, suitable for company intranet. n-dependent Internet customers: can Access to the Internet and access to the operating system is integrated on a client machine. N Enhanced Internet Customers: Microsoft Office 97 and Microsoft Visual Studio.
(2) Business services: Integrate the server-based Microsoft product with custom COM components to operate in one piece. N Web Services (Microfsoft Internet Information Server and Active Server Pages). N Transactions and Component Services (Microsoft Transaction Server and COM). N Message Services (Microsoft Message Queue Server). n General Data Access (Microsoft Data Access Excess) l Operation of Main Machine Environment (Microsoft SNA Server). The details are listed in the topic below.
(3) Data services:
n Microsoft SQL Server7 Database. N Microsoft Exchange Server 5.5 version of the directory and information library.
Topic: Business Services
One: Microsoft Internet Information Server and Active Server Pages). Web Services Object Model: 1. Server Object: Provides access to the method and attribute on the server. Example: Questional Data Access (Microsoft Data Access Member) SetObjmyObject = Server.createObject ("BusinessServer.MyruleObject") 2: Session object: The information required to store a specific user session. 3: Application object: Used to make all users of an application share interests. 4: REQUEST object:. 5: Response object:. 2: Transaction and component service (Microsoft Transaction Server and COM) 1: Microsoft Transaction Server (MTS) is a component-based transaction system to meet complex transactions. MTS supports the database of XA protocols of SQL Server and An OEB-based X / Open algorithm (see annotation). The services provided by MTS are: N support for distributed transactions. n Services for controlling instantiation and use of objects. Automatic management of n processes and threads. N object instance management. n Database Connection Management (Connection Pool). In the application, the corresponding components can be declared completion of the above services. 2: MTS and SQL Server transactions, require atomic execution, or throughout success, the entire failure. Transaction Server and Microsoft Distributed Transaction Coordinator (MSDTC) Interaction Confirmation The transaction meets the ACID (atomic Atomicity, consistency consistency, separation isolatation, and durability durability). 3: The difference between MTS and SQL Server transactions. MTS can be implemented with Visual Basic, Visual C and other packaged MTS components. SQL Server transactions can only be written by Transact-SQL code, such as (ADO). 4: Windows DNA (Windows Distributed Internet Application Architecture): Develop customer / service mode with Web and a strategy together. Use HTML, DHTML, Active Server The first layer (expression layer), MTS, and MTS components, such as IIS (Internet Information Server), IIS / ASP components, and ASP scripts occupying the intermediate layer (business logic layer), SQL Server as the data service layer. 5: MTS uses the Distributed Transaction Coordinator, DTC) Transaction Engine. DTC uses two segment delivery standards. Information about DTC can be obtained by using MMC (Microsoft Management Console) Open C: /Winnt/System32/Services.msc, and find the DTC service in the list, and look at its properties. 6: Use MTS to maximize system performance. (Precautions) n Avoid passing or returning objects. n Use the value (BY VAL) to pass the parameters. (BY VAL Keywords minimize journey between networks) n Avoid creating database cursors. Use less RECORDSET objects. n By making the object package container threaded, MTS can perform concurrent customer requests in multiple objects. 7: Note: XA is a two-phase submission protocol defined by the X / Open organization, allowing transactions during multiple database services to be coordinated and regarded as a transaction.
(UNIX database, including Oracle, Informix, DB2) Three: Message Services (Microsoft Message Queue Server). 1: Microsoft Message Queue (MSMQ) provides an asynchronous communication function for the application. MSMQ is considered to be a bridge in the connection distributed application. 2: MSMQ automatically integrate with MTS. The application can encapsulate the MSMQ message in the MTS transaction. 3: MSMQ and the different Microsoft Exchange servers. EXChange provides messaging for users to users (Person -to -Person). The MSMQ provides messaging for applications to Application - to -Application. 4: Universal Data Access (UNIVERSAL DATA Access) Data Access Members across the boundaries between business service layer and data service layers. ADO, OLE DB (Embedded Database) and ODBC together form a Microsoft Data Access Configuration (MDAC). 5: Interoperability of Main Machine Environment (Microsoft SNA Server) Microsoft COM & DCOM (Introduction) 1: COM is a definition object The server interacts with the object customer. Object Server is a module that implements COM classes. Object Consumer is a module that uses COM objects. DCOM extends the COM protocol, making the object server can be located in a computer different from the customer. Call the object server via the RPC. (CORBA is also a distributed object protocol) COM manages the security of objects via SSPI (Security Support Provider Interface, Security Support Provider). 2: Application Server (Intermediate Layer) The characteristics should be available: N distortion start, monitor, and abort. n Scalable ability.
N is easy to configure.
n Security failure.
Far-level startup function: If the user wants to create a COM object on the remote computer, the DCOM Service Control Manager (SCM) on the remote computer will automatically start the COM server and make the COM object. The specific information can run the DCMCNFG command in the Start menu. Easy to configure the ability: Right-click on a COM DLL or EXE in the Windows Explorer to activate registration or revoking registration. Scalable capabilities: scalable first level and second level. Two load balancing provided by DCOM. 1), static load balancing (specifying the running machine of the application server), specified in the properties of the application in the DCMCNFG. 2): Dynamic load balancing, allocated by the scheduler. Delphi provides related technologies: U COM / DCOM / COM business object. u Corba business object. U XML / HTML U CGI / SAPI / NSAPI U ASP U Active X (Active Form) U Ado / OLE DB U MTS Object U MIDAS Server U CORBA Server. Related components in 1) File menu / New / Multitier and ActiveX pages. 2) ADO, MIDAS, Internet Express, ActiveX and other pages in the component panel. Introduction to CORBA 1: What is CORBA (Common Object Request Broker Architecture)?
CORBA is a distributed object standard structure defined by Object Management Group (OMG). Language neutral, using object-oriented design structure, allowing software objects to be reused in different operating system platforms and applications. If you want to implement a function, CORBA is a better solution: l Application system To integrate heterogeneous platforms and operating systems. l The application server must be executed in the Linux / UNIX machine. l The application system must perform a critical task, with secure powerful fault tolerance, must be stable and efficient. l To develop Internet / IntraNet solutions using web objects. l Application system future wants to integrate with Java. 2: The Corba's Structure CORBA object is a component that provides a specific service that declares the available services by defining a set of output interfaces. In this output interface, the CORBA object defines the methods and access properties that the client can call. The client can specify the name of the CORBA object that provides the service, and the method to be called or the attribute to access can be available from ORB to get the CORBA object. Terms: Orb: Object Request Broker. Joint client and intermediary CORB objects. Stub object: Run the replica of the CORBA object of the client, call the Stub object on the client, then the Stub object calls the CORBA object remotely through the ORB, the Stub object uses Marshaling (object pointer conversion, making the other program to identify) automatic Transfer parameters and data. Skeleton object: Objects running on the server, restore the data passed to the server into the server side using the format. The CORBA object is then called according to the automatic requirements according to the client. Call mode: u Static call: The client program passes the data to the CORBA object via the Stub object. After the CORBA object is executed, the result is returned back to the client's Stub object through the Skeleton object. After replying to the data format via the Stub object, Give the client's application. Dynamic Interface Invocation DII: The client does not need to have a Stub object, nor does it need to know the methods and properties provided by the remote CORBA object, and the CORBA program can get this information when executed, and then dynamically call the CORBA object. DII has a greater elasticity than static calls, but the programming is difficult, and the performance efficiency is not as static. 3: Core service provided by CORBA
N Event Service: The "Provider-Consumers (Supplier_Consumer) model passes an event to the consumer object in asynchronously through an event signal.
n Naming Service: Allow programmers to use class-type ways to name the business object, and then use these meaningful names in the program to access these objects.
n Transaction Service: Provides a distributed application to perform a critical task, allowing business objects to transaction management between the heterogeneous platform and the database data.
N Security Service: Access Control, Auding, Authentication, Access Policy Control (PLICY Control).
