In the software development in previous years, the two-tier structure occupied a very important position. Two-tier architecture still exists widely, but it has many shortcomings, such as high maintenance cost of client and difficulty in distributed processing. With the addition of more layers between the end users and the back-end services of the two-tier structure, the multi-tier structure appears.
The classic three-layer theory divides the application into three levels, as shown in Figure 2-63.
The presentation layer is used to deal with human-computer interaction. At present, the two most mainstream presentation layers are Windows format and WebBrowser format. Its main responsibility is to handle user requests, such as mouse clicks, input, HTTP requests, etc.
The domain logic layer simulates the actual activities in the enterprise, and can also be considered as the model of enterprise activities.
Data source layer, dealing with database, message system and transaction system.
In practical application, there are some changes in the three-layer structure. For example, in Windows. NET system, the application program is divided into three levels: presentation layer, business layer and data access layer, which correspond to the three levels in the classic three-tier theory. It is worth mentioning that. NET system can directly access the data access layer, that is, recordset technology. In ADO.NET, this technology is very mature, and it has achieved very friendly functions through some data-aware components in the presentation layer. This cross-layer access technology is generally not allowed because it may destroy the dependencies between layers. In the Windows platform, strictly following the guidelines means a lot of extra work. Therefore, we can see that the standard is not static.
In this system, the data access layer should be further divided into basic data access layer and business data access layer. The former mainly completes database access and transaction processing, while the latter inherits the basic data access objects of tables in the database to realize its own data access requirements. Because this system involves graphic configuration and interface data interaction, the presentation layer adopts desktop mode and IE mode, business operations are mainly carried out in IE, and workflow configuration and data interface with P3 (or MS Project) are mainly completed in desktop mode.
Figure 6-63 Schematic Diagram of Layered Development
2. Service-oriented architecture
SOA (service-oriented architecture, also called service-oriented architecture or service-oriented architecture) refers to the software system architecture that is realized by connecting independent functional entities that can accomplish specific tasks in order to meet the needs of business integration under the Internet environment. SOA is a component model, which connects different functional units (called services) of an application through well-defined interfaces and contracts between these services. Interface is defined in a neutral way, and it should be independent of the hardware platform, operating system and programming language that implements the service. This enables services built in various such systems to interact in a unified and universal way.
The system adopts service-oriented architecture, with high internal cohesion and low coupling between components, which improves the maintainability, expansibility and portability of the system.
3. Adopt the object-oriented design method.
This system adopts object-oriented programming method. The main purposes of object-oriented software development are: using reusable software technology to speed up problem solving, shorten development time and reduce software development cost; When the software function changes, it is only necessary to modify the implementation method of one or more classes to localize the influence of the software function change, thus reducing the cost of software maintenance. The main challenge of object-oriented software design is to decompose the software system into basic data types or classes and subclasses, and define the characteristics of each basic class and subclass. In the concrete implementation, we standardized the part with * * * in the design and compiled it into the parent class. Public data and processing are defined in the parent class, and other subclasses inherit from the parent class and expand appropriately according to special requirements.
In the specific implementation process, we adopted the following methods:
(1) Encapsulation of using objects: We have strictly encapsulated the code of the basic class library, and the changes and upgrades of the class library will not affect the programs that use the class library, thus improving the maintainability of the programs.
(2) Using multiple inheritance: We will use common functions, such as inserting, deleting, modifying, saving data, sorting, filtering, searching, replacing data, printing tables, etc.
(3) Using polymorphism: Polymorphism brings great flexibility to programming. We use polymorphism to provide a unified access interface for similar functions in different environments and enhance the readability of the program.
4. Distributed computing technology
There are many distributed technologies, such as CORBAR and COM+. Yes. NET platform, as well as WEB services and Net Remoting technology. Web service is a new distributed computing technology, which can cross the boundary between application system component model and operating system programming language and be called by clients or other servers.
Web service is a new method to perform remote method calls on HTTP using SOAP. This problem has been very difficult in the past, because using DCOM (Distributed COM) was very troublesome in instantiating the objects of remote servers, using methods and obtaining results, and required high skills when making necessary configurations.
The system adopts Web service to realize distributed structure, and distributed transactions pass through. Net enterprise services.
Implicit distributed transaction implementation:
The biggest advantage of implicit distributed transaction is that it does not need to control the transaction manually, and a transaction range is declared through code blocks, and the operations within this range will automatically enter the transaction. This transaction mode is through. Net enterprise services.
Show distributed transaction implementation:
Show distributed transactions. Manually obtain the transaction from DTC, associate the transaction with the connection that needs to enter the transaction, and manually commit or rollback the transaction. This transaction mode is through. Net enterprise services.
5. Integration with workflow engine
The workflow system used in this system integrates computer communication technology, component technology and graphics technology, and its practicability, advancement and reliability have reached the leading level in China.
6. Using VML technology to draw the schedule in the browser.
Drawing on the browser has always been a difficult step for many software companies. The system adopts VML technology for the following purposes
Figure 6-64 Schematic Diagram of Workflow System
The user provides the function of drawing the schedule directly in the browser, and can track the schedule, as shown in Figure 6-64.
The progress chart in the system has two forms: single code and double code, and can be converted to each other.
7. Perfect combination and tight integration with Microsoft 0ffice software.
Microsoft Office is a commonly used office software. Many documents in the process of project management, such as work contact list and design change list, are mostly in Word format, while some reports are in Excel format, so the system is required to be seamlessly connected with Microsoft Office suite. Emphasizing the integration with Microsoft Office is not only convenient for users to use, but also protects users' investment in Microsoft Office to the greatest extent.
8. Integration with electronic signature and handwriting technology
With the increasing demand for the security and authenticity of documents in project management, especially handwritten signatures and electronic seals, Word/Excel documents are required to be signed and sealed, and functions such as multi-person countersigning, signature verification, authentication and non-repudiation need to be realized. According to the actual situation, Dongfang Thinking adopts the third-party software iSignature (which has passed the security inspection of the Ministry of Public Security) to manage the handwritten signature electronic seal software. The scheme adopts information encryption and data compression processing technology, which has good reliability and strong expansibility and is widely used in government and enterprises.
ISignature handwritten signature electronic seal software consists of signature key disk and software. The signature key disk has its own CPU, fast memory and encryption processing mechanism, which is used to store digital certificates, seal information or signature information of companies or individuals. The signature key disk is connected with the computer through USB interface. The software is automatically embedded in Word/Excel to seal or sign.
9. integrate with SMS cat
Integrate with the third-party product GSM-SMModem short message cat, realize the short message sending and receiving function, remind the task to be processed or send a notice in time.
10.OWC technology
OWC, namely Office Web Components, is a collection of component object model (COM) controls, which can be used to publish spreadsheets, charts and databases to websites. They can also be used to view these published projects and data access pages. The data exchange and storage between tables and database are realized by using the technology of "table template label", which solves the problem that the program needs to be revised repeatedly on each table because of different tables in different expressway projects (generally about 400 sheets per project).
The system adopts Microsoft OWC technology, with intuitive interface and simple operation. All kinds of tables operated in the system are consistent with those operated in Excel tables and conform to the user's habits. The efficiency of filling in form data is improved. The report format can be customized and output conveniently.
1 1. It can be easily integrated with Biztalk Server.
Biztalk is an XML-based data exchange standard, and Biztalk Server is Microsoft's enterprise application integration server, and the data exchange standard between them is Biztalk.
The system can be easily integrated with OA and other systems through Biztalk Server, including processes.
12. Single sign-on technology
Single sign-on adopts encryption and digital signature technology based on digital certificate, implements centralized and unified management and identity authentication for users, and serves as a unified login entrance for this system and other application systems. At the same time, it issues login tickets for all application systems to legal users who have passed identity authentication, thus realizing "single sign-on and multi-point roaming".
13. Mobile operation of PDA
Figure 6-65 Mobile Operation of Handheld Equipment
The system adopts SmartClient technology to provide the mobile operation function of PDA. For example, quality inspection and evaluation, the field inspection data can be collected directly through PDA, and then synchronized with the server data through synchronization mechanism.
14. multithreading technology
By default, only one thread in an application process is performing tasks, but the system often performs CPU-consuming tasks such as file compression and data transmission. If single thread is used, the overall performance of the system will decrease.
The system adopts multi-thread technology, and enables new threads to execute complex tasks, thus ensuring the performance of the system.
15. Application of Enterprise Library 2.0
Enterprise library is a set of basic components provided by Microsoft for enterprise development, which fully realizes the configuration and use of XML, including data access, security, logging, exception, encryption/decryption and other services. Compared with 1.0, Enterprise Library 2.0 has changed a lot, with more perfect functions and simpler use. The system adopts Enterprise Library 2.0 and has been redeveloped to make it more suitable for the application of this system.
16.Ajax technology
Ajax uses a series of technologies that enable browsers to provide users with a more natural browsing experience. Before Ajax appeared, websites forced users to enter the submit/wait/redisplay paradigm, and users' actions were always synchronized with the "thinking time" of the server. Ajax provides the ability to communicate asynchronously with the server, thus freeing users from the cycle of request/response. With the help of Ajax, you can use JavaScript and DHTML to update the UI immediately when the user clicks the button, and send an asynchronous request to the server to update or query the database. When the request returns, you can use JavaScript and CSS to update the UI accordingly, instead of refreshing the whole page. Most importantly, users don't even know that the browser is communicating with the server: the website seems to respond immediately.
Ajax technology has been widely used in the system, which improves the efficiency of the system and enhances the user experience.