Basic knowledge of web development

Reference: http://www.cnblogs.com/xdp-gacl/p/3729033.html

I. Basic concepts 1.1, Web development related knowledge

Web, in English, the web means the Web page, which is used to represent the resources that the Internet host is available for outside access.
Web resources on the Internet for external access are divided into:

1. Static Web resources (such as HTML pages): Data that is accessible to people in a Web page is always the same.
2. Dynamic Web resources: refers to the Web page for people to browse the data is generated by the program, at different points of time to access the Web page to see the content varies.

Static Web Resource development technology: Html
Common Dynamic Web Resources development technology: Jsp/servlet, ASP, PHP, etc.
In Java, Dynamic Web resource development technologies are collectively referred to as Javaweb.

1.2. Web Application

Web applications means browser-accessible programs, often referred to as Web applications. For example, there are a.html, b.html ... multiple Web resources, which are used to provide services externally, these Web resources should be placed in a directory to form a Web application (or Web application)
A Web application consists of several static Web resources and dynamic Web resources, such as HTML, CSS, JS files, JSP files, Java programs, support jar packages, configuration files, and so on.
　　After the development of Web applications, if you want to be accessible to the outside world, you need to give the Web application directory to the Web server management, this process is called virtual directory mapping

1.3. Web History

Two phases of web development: static, dynamic

1.4. Static Web

*htm, *html, these are the Web page suffix, if now on a server directly read the content, it means that the content of these pages through the Web server display to the user. The process diagram for the entire static web operation is as follows:

In a static Web program, the client uses a Web browser (IE, Firefox, etc.) to connect to the server, use the HTTP protocol to initiate a request, tell the server which page I need to get now, and all the requests to the Web server. The Web server then extracts the content from the file system (the disk that holds all the static pages), depending on the user's needs. After the Web server is returned to the client, the client receives the content after the browser rendering parsing, to get the effect displayed.

　　There are several drawbacks to the static Web:

　　1, the content of the Web page can not be updated dynamically, all users see the content and the final effect is the same.

In order to make the static web display more attractive, you can add JavaScript to complete some of the page display effects, but these effects are on the client with the help of the browser display to the user, so on the server itself does not have any changes.

means to implement static Web client dynamic effects:

• Javascript
• VBScript

JavaScript is used most in real-world development.

　　2, static web can not connect to the database, can not implement and user interaction.

Using a database to save data is now a choice for most systems, because data can be easily managed in the database, and additions and deletions can be done using standard SQL statements.

1.5. Dynamic Web

The so-called dynamic does not mean that the page will move, the main feature is: "The Web page display effect due to people change", and Dynamic web has interactivity, the content of the Web page can be updated dynamically. The process diagram for the entire dynamic web operation is as follows:

In the Dynamic web, the program still uses the client and the server, the client still uses the browser (IE, Firefox, etc.), connects to the servers over the network, uses the HTTP protocol to initiate requests (request), and all requests now go through a Web server Plugin (server plug-in), which is used to differentiate whether a static resource is requested (*.htm or *.htm) or a dynamic resource.

If the Web server plugin discovers that the client is requesting a static resource (*.htm or *.htm), the request is forwarded directly to the Web server, after which the Web server takes the content out of the file system and sends it back to the client browser for resolution execution.

If Web Server plugin discovers that the client is requesting a dynamic resource (*.jsp, *.asp/*.aspx, *.php), the request is forwarded to the Web Container (Web container), the database is connected in the Web Container, After a series of operations, such as extracting data from a database, and then dynamically piecing together the contents of the page, putting together the content of the page, all the content is presented to the Web server, and then the content is sent back to the client browser through the Web server for parsing and execution.

1.6, Dynamic Web application implementation means

Dynamic web is now implemented in a number of ways, the more common are the following:

• Microsoft asp, ASP.
• Php
• JAVA servlet/jsp

1. Microsoft asp, ASP.

Microsoft Dynamic Web Development is relatively early, and the earliest in the domestic most popular is the ASP. ASP is in the HTML language to add the VB Script, but the standard development application should be used asp+com, but the actual situation, in the development of ASP is basically in a page to write hundreds of thousands of code, page code is extremely chaotic.

The ASP itself has the limitation of development platform: Windows+iis+sql server/access,asp can only run on Windows operating system, ASP is now basically obsolete, This is mostly done with ASP. ASP. NET has improved performance and developed rapidly, but it is still limited by the platform. Asp. NET is primarily used in the C # language.

2.PHP

PHP Development is fast, powerful, cross-platform (platform refers to the operating system), and the code is simple.

3.servlet/jsp

This is the implementation language of the B/s architecture that Sun (which Sun has now been acquired by Oracle) and is based on the Java language, because the Java language is simple enough and clean.

The performance of servlet/jsp technology is also very high, not limited by the platform, each platform can be used basically. And in the run is the use of multi-threaded processing, so the performance is very high.

Sun's first launch of the Web technology introduced a servlet program, the servlet program itself, there are some problems, all the program is written in Java code +html, that is, to use the Java output statement, a line of output all the HTML code, and then , Sun has been inspired by the ASP, the development of JSP (Java Server Page), JSP some code writing effect and ASP is very similar. This makes it easy for some ASP programmers to turn to JSP learning and increase the market competition.

Basic knowledge of web development