A .Java 2 platform has three versions:
1. the Java ME: for small devices and smart card of the Java 2 Platform Micro Edition ( the Java 2 Platform Micro Edition )
2. the Java SE: the Java 2 Platform, Standard Edition for desktop systems ( the Java 2 Platform Standard Edition )
3. the Java EE for creating server applications and services, Java 2 Platform, Enterprise Edition ( the Java 2 Platform Enterprise Edition )
Two .B / S structure and C / S structure
1.B / S architecture (Browser / Server, Browser / Server mode), is a WEB A network structure model after the rise, WEB browser is the client main application software . This model unifies the client, will focus on the core of the system function to the server, simplifying system development, maintenance and use. Just install a browser (Browser) on the client, such as Netscape Navigator or Internet Explorer , server installed the Oracle , Sybase , Informix , or SQL Server and other databases. Browser by Web Server for data exchange with the database.
2. Client / server network, Client / Server . In a client / server network, the server is the core of the network, and the client is a network-based, client server rely obtain the required network resources , and the server provides the client with the necessary network resources.
Difference 3.B / S, C / S is
A. Different hardware environments:
C / S is generally based on a dedicated network, on a small scale network environment, and then provide a connection and exchange data between a local network services through a dedicated server.
B / S based on the wide area network, not necessarily a dedicated network hardware environment, for example, the Internet and telephone, rent equipment. own information management. there are more than C / greater scope to adapt S, generally as long as the operating system and browser on the line
B. Security requirements for different
C / S is generally oriented relative to the fixed user base, a strong ability to control information security generally highly confidential information system using C / S suitable structure may be public information by B / S distribution section.
B / S builds on the wide area network, the ability to control the security of the relatively weak, is facing the unknown user base.
C. Different procedural framework for
C / S program can pay more attention to the process, multi-level permissions can check on the operating speed may be considered less.
B S multiple considerations / security and access speed required to establish the basis of a more optimal in above. ratio C / S has a higher request procedural framework B / S structure is the trend, from a .Net series BizTalk MS 2000 Exchange 2000, a comprehensive network support member built systems. IBM and push the SUN the JavaBean component technology, so that B / S is more mature.
D. Different software reuse
C / S program may be considered unavoidable integrity, reusability member as good as in the reusability of components in B / S requirements.
Multiple structure B / S pairs, requires independent functional components. Relatively better reuse. bought on the table can be reused, rather than doing a wall of stone table and
E. Different system maintenance
System maintenance is the software life cycle, spending big, important -------
C / S program due to the integrity, must examine a whole, deal with emerging problems and system upgrades. Upgrading difficult. Probably do a whole new system
B / S composed of members, the replacement of individual aspects member, seamless upgrade the system. the system maintenance overhead is minimized. online users themselves can be downloaded from the upgrade installed.
F. Deal with different
C / S can handle the user plane is fixed, and in the same region, requiring high security requirements associated with the operating system. The system should be the same
B / S established over the WAN, for different user groups, geographic dispersion this is a C / S can not be done. minimal relationship with the operating system platform.
G. The user interface of different
C / S are mostly built on the Window platform, the performance of the method is limited, programmers generally require a higher
B / S based on the browser, there are more rich and vivid expressions to communicate with users. And most difficult reduce, reduce development costs.
H. Traffic from different
C / S is a typical procedure generally centralized mechanical processing, relatively low interactivity
B / S can change the flow of information, information such as changes in BB BC BG, it flows more like trading center
Example 4:
Usually loaded on the PC, office and entertainment software is C / S structure, and because now B / S technology with respect to the C / S is still not very mature, so many large erp is still C / S structure, but there are trends steering B / S is
Three rich client technology:
1. fat client (rich client) application:
Fat client is relative to the thin client in terms of the application process will be divided into two parts: the handling and processing of some centralized server part of the client portion of a user's desktop computer to perform. The client portion of the fat client application program interface UI will in addition be responsible for display to the user to interact, but also responsible for most of the business logic processing. This type of application requires the client part of the ability to perform tasks, the requirements of the client machine is relatively high, but the server is made possible to reduce a portion of the pressure, reduce the requirement for server performance. A typical fat client applications contain one or more applications running on the server and the client PC, install the feature-rich interactive user interface on the client PC,
users can view and manipulate data through this interface, processing business affairs, or all of the business logic processing part shared server (fat client so it is very "fat", so called fat client, also called rich client). Centralized access server part of the general data processing operations, is also responsible for processing part or all of the business logic.
2. The thin-client applications: mainly refers to thin-client application Web application B / S structure, he is actually a variant of C / S structure of it C / S structure, client program unification. browser (broswer), the browser parses the HTML standards to display only the user interface. Thus, the server handles the business logic and access data, and then transmits the processed results as HTML to the client, end responsible for the results displayed to the user, in addition to the client is responsible for validating data and organize outside, basically does not process any business logic, only focus on the user interface display. (such thin clients becomes very thin, so called Thin Client)
3. both architecture corresponding to: fat client with respect to traditional network applications C / S for the structure, with respect to the thin client Web applications are generally B / S is a structure.
4. Existing rich client technology:
A.Laszlo
Laszlo is an open source rich client development environment. When using the Laszlo platform, developers only need to write a description language called LZX, Laszlo platform will run on the J2EE application server compiled into SWF file format and transmitted to the client display. In future plans, Laszlo LZX can also be compiled into Java or .NET native code, thus greatly improving the operating efficiency.
②Java SWT
Java several years there have been, and fully supports the creation of forms-based user interface. It can be used through a Web browser Java plug-in software, or using Java Runtime Environment newer Java Web Start technology to deploy the application.
B.XUL
XUL is an XML-based user interface language, it comes from the Mozilla open source project. It can be used to establish Forms applications, these applications can not only run on the Mozilla browser, but can also run on other engines are described, such as Zulu (a Flash MX component) and Thinleys (a Java implementation).
C.Bindows
Bindow with Javascript and DHTML development of Web Forms framework. Javascript for displaying and processing client interface, XMLHTTP for transmission from the client to the server. Javascript expressive client is no doubt that the use of Javascript can almost achieve most of what Windows applications capable, XMLHTTP has been often used to implement the "no refresh" the Web page, and Javascript with it, you can complete the data from the server and client transmission.
D.Avalon
Avalon is part of Microsoft's next version of Windows (code-named Longhorn), is a graphics and presentation engine, gathered together by a group of major new class added to the .NET framework. Avalon defines a new markup language used in Longhorn, which is code-named "XAML" (Extensible Application Markup Language). XAML can be used to define the text, image and control layout, program code may be embedded directly into XAML, it may be retained in a separate file. This is in Flex MXML or Laszlo LZX is very similar. The difference is that Avalon application must run on Longhorn-based environment, while Flex and Laszlo are not dependent on the platform, only need to have the Flash player browser.
E.Flex
Flex's goal is to allow programmers to quickly and easily develop RIA applications. In the development of a multi-layer model, Flex presentation layer belonging to the application. Flex uses GUI interface development using XML-based MXML language. Flex has a variety of components, enabling Web Services, remote objects, drag and drop, column sorting, charts and other functions; FLEX built-in animation effects and other simple interactive interface. With respect to HTML applications (such as PHP, ASP, JSP, ColdFusion and CFMX, etc.) need to be performed based on templates on the server side at the time of each request, because the client only needs to load once, FLEX workflow applications has been greatly improved. FLEX language and file structure also tried to separate the application logic from the design. Flex is a client and server XML Web Services and remote objects (Coldfusion CFCs, or Java classes and other objects to support the Action Message Format) communication path between.
IV. Embedded Development
1. embedded systems and embedded operating system differences:
(1) Embedded Systems
Application-centric, computer technology , software and hardware can be cut to meet the application system functionality, reliability, cost, size, power consumption strict requirements dedicated computer system.
Development of embedded technology generally speaking can be divided into four stages:
A. The first stage is a single chip as the core in the form of a programmable controller system, while having the monitoring, servo, a pointing device cooperating features. This system is used in some of the most highly specialized industrial control systems, generally do not support the operating system direct control over the system through assembly language programming, after the end of the run to clear the memory.
B. The second stage is embedded CPU is based on a simple operating system as the core of embedded systems. This phase of the operating system has some compatibility and scalability, but the user interface is not friendly enough.
C. The third stage is marked by an embedded operating system for embedded systems. The main feature of this phase of the system are: an embedded operating system to run on a variety of different types of microprocessors, good compatibility; operating system kernel fine, high efficiency, and has a high degree of modularity and scalability; comprising file and directory management, device support, multitasking, network support, a graphical user interface window and other functions; a large number of application program interface (API), to develop applications simple; rich embedded applications.
D. The fourth stage is marked by Internet-based embedded systems, this is a rapidly developing stage. Most embedded systems are also isolated from the outside Internet, but with the development of Internet and Internet technology and information appliances, industrial control technology, combined with the increasingly close combination of embedded devices and the Internet will represent the real future of embedded technology .
(2) embedded operating system
Embedded operating system is a versatile software system, widely used in the field of industrial control and defense systems, and communications equipment. Allocation, scheduling work all the software and hardware resources of embedded operating system is responsible for embedded systems, concurrency control coordination activities; it must reflect the characteristics of the system in which it is possible to achieve the required functionality of the system by handling certain modules. At present, some more successful application of embedded operating system products are many, such as Vxwork, QNX, PalmOS, Windows CE and so on.
2. Embedded Development:
Embedded Development refers to embedded operating systems developed under
3. Application:
Embedded system is undoubtedly one of the most popular of the most promising IT applications. Embedded systems in certain equipment, devices generally these hardware resources (processor, memory , etc.) is very limited, and the cost is very sensitive, and sometimes very high requirements for real-time response. Especially with the intelligent consumer appliances, embedded even more important. As we normally common to mobile phone, PDA, electronic dictionary, video phone, VCD / DVD / MP3 Player, digital camera (DC), digital video cameras (DV), U-Disk, set-top box (Set Top Box), high-definition television ( HDTV), game consoles, smart toys, switches, routers , CNC equipment or instrumentation, automotive electronics, home appliances control systems, medical equipment, aerospace equipment, etc. are typical of embedded systems.