JavaWeb Study ( One )—WEB Introduction to development

01 Concept

• What is? WEB？WEB The classification of ？

  seeing the name of a thing one thinks of its function ,WEB It’s web pages . The web page is used to represent the resources on the network host for external access .WEB Resources can be divided into static WEB And dynamic WEB. static state WEB It means that the data in the web page for customers to browse is always the same , Usually by html Technical realization ,JavaScript You can achieve some dynamic effects on the basis of static pages , But these special effects are displayed to users on the client side with the help of a browser , So there’s no change in the server itself .** static state WEB Unable to connect to database , Can’t interact with users ;** dynamic WEB On the contrary , The data in its web page for customers to browse can change dynamically , The rules of change are controlled by procedures , Visit at different times WEB There are differences in what the page sees . dynamic WEB Be able to connect to the database , Interact with users .

• Common dynamics WEB Resource development technologies include ：

  • **JSP/Servlet ：**HTML nesting Java Code , Good performance , Cross-platform support .

  • **ASP： ** stay HTML On the basis of VB Script , Cannot cross platform , It can only run on windows On the operating system . Basically eliminated .

  • **PHP：**PHP The development speed is very fast , Powerful , Cross-platform support , Code writing is simple .

• What is? WEB Applications ？

  WEB An application is a program for a browser to access , It’s also commonly referred to as web application . One web The application consists of multiple static web Resources and dynamics web Resource composition , Such as :html、css、js file ,Jsp file 、java Program 、 Support jar package 、 Configuration files, etc .Web After application development , If you want to be accessible , Virtual directory mapping is required , hold web Give the directory where the application is located to web Server management .

• What is? WEB The server ？

  Web A server is a program that resides on some type of computer on the Internet , It’s a program that can provide documents to the requesting browser . When Web browser （ client ） When connecting to the server and requesting files , The server will process the request and feed the file back to the browser , The accompanying information tells the browser how to view the file （ I.e. document type ）.

  The server is a passive program ： Only when Internet When a browser running on another computer makes a request on , The server will respond .

• frequently-used WEB The server

  • WebLogic： The United States BEA Company produce , take Java Dynamic functions and Java Enterprise Standard security is introduced into the development of large-scale network applications 、 Integrate 、 Deployment and management , Is currently the most widely used Web The server .
  • WebSphere：IBM The core part of the company’s e-commerce plan , It is based on Java Application environment , For building 、 Deployment and management Internet and Intranet Web Applications .
  • IIS：Microsoft Produce ,IIS Is allowed in public Intranet or Internet Who posted information on Web The server .IIS Provides a graphical interface management tool , be called Internet Information Service Manager , Can be used to monitor configuration and control Internet service .
  • **Tomcat:** Blowing up ！Tomcat It’s an implementation JAVA EE The smallest of standards WEB The server , yes Apache Software foundation Jakarta A core project in a project , Advanced technology 、 Stable performance , And open source is free ！ Study JavaWeb Development generally uses Tomcat The server , The server supports all JSP as well as Servlet standard .

02 dynamic WEB How it works

dynamic WEB in , The program still uses the client and the server , The client is the browser , Connect to the server over the network , Use HTTP The agreement initiates the request , All requests are first WEB Server Plugin Handle , The plug-in is used to distinguish between dynamic and static requests . If WEB Server Plugin It is found that the client requests static resources , The request is forwarded directly to WEB The server , after WEB The server pulls content from the file system , Send it back to the client browser for parsing execution . If WEB Server Plugin It is found that the client requests dynamic resources , Then forward the request to WEB Containers , stay WEB Connect database in container , After a series of operations, such as fetching data from the database, the display content of the dynamic patching page , After piecing together the display content of the page , Give all the presentation to WEB The server , After through WEB The server sends the content back to the client browser for parsing .