One of the JSPs Web application overview

Introduction of C/s and/b applications

? Introduction to C/S application

c/S (CLIENT/SERVER) structure, which is the client and server structure. It is often said that the FAT client software architecture, through which can make full use of the advantages of both ends of the hardware environment, the task is reasonably distributed to the client side and server side to achieve, reducing the communication overhead of the system. At present, most application software systems are two-layer structure in client/server form. For example, the network game is the C/S model developed, want to play online games must be installed on the computer client software, and a lot of business processing is done on the client. Typically, the C/S mode is not strongly dependent on the network.

? c/S model merits

(1), application server running data load lighter.
The simplest database application of the C/S architecture consists of two parts, the client application and the database server program. The two can be called foreground program and background program, respectively. The machine running the database server program, also known as the application server. Once the server program is started, it waits to respond to requests from the client, and the client application runs on the user's own computer, corresponding to the database server, which can be called a client computer, and when any action is required on the data in the database, the client automatically looks for the server program and makes a request to it. The server program responds to the predetermined rules, sending back the results, and the application server is running with less data load.

(2), the disadvantage of C/s architecture is high maintenance costs and large investment.
First, the use of C/S architecture, to select the appropriate database platform to achieve true "unity" of database data, so that the distribution of data synchronization between the two places is completely managed by the database system, but the logic of the two operators to directly access the same database can be effectively implemented, there are some problems, if need to establish "real-time" Data synchronization, it is necessary to establish a real-time communication connection between the two places, to keep the database server online operation, network management staff both to server maintenance management, but also to the client maintenance and management, which requires high investment and complex technical support, maintenance costs are high, maintenance tasks are large.
Secondly, the traditional C/s structure software needs to develop different versions of software for different operating system systems, because of the rapid upgrading of products, high cost and low efficiency have not adapted to the work needs. After the emergence of a cross-platform language such as Java, the B/s architecture is a fierce impact on C/s, and it forms a threat and challenge.

? b/S Application introduction

b/S is browser/server. b/S Basic is browse-webservice-db such a structure. The thin client that is commonly said. Almost all of the services in this structure are handled on the service application side. The advantage is that the client requirements are not high, a browser is generally possible, and easy to verify permissions.

? b/S model merits

(1), maintenance and upgrade method is simple.

At present, the improvement and upgrading of software system is more and more frequent, and b/s structure products clearly embodies more convenient characteristics. For a slightly larger unit, if the system managers need to run back and forth between hundreds of or even thousands computers, the efficiency and workload is conceivable, but B/s architecture of the software only need to manage the server on the line, all the client is just a browser, there is no need to do any maintenance. Regardless of the size of the user, how many branches will not increase any maintenance upgrade workload, all operations only need to target the server, so the client more and more "thin", and the server is more and more "fat" is the future trend of information development. In the future, software upgrade and maintenance will be more and more easy, and the use will be more and more simple, this to users of human, material, time, cost savings is obvious, amazing. Therefore, the way to maintain and upgrade the revolution is "thin" client, "fat" server.

(2), cost reduction, choose more.
As you all know, Windows is almost eminence on desktop computers, browsers become standard, but Windows is not in absolute dominance on server operating systems. Now the trend is to use the B/s Architecture Application management software, just installed on the Linux server, and high security. So the choice of server operating system is many, regardless of the use of that operating system can make most people using Windows as a desktop operating system PC is not affected, which makes the most popular free Linux operating system quickly developed.

(3), the application server running data load is heavier.
Because b/s architecture management software is only installed on the server side (server), network managers only need to manage the server on the line, the user interface main transaction logic on the server side (server) completely through the WWW browser implementation, very few transaction logic in the front-end (Browser) implementation, All clients are only browsers, and network administrators only need to do hardware maintenance. However, the application server is running a heavy load of data, once the server "crashes" and other issues, the consequences are unimaginable. Therefore, many units have a database storage server, just in case.

Introduction to Application Server and Web server

We usually say that the server is actually a computer with special configuration and efficacy, is a machine.

The application server or Web server we mentioned here refers to a software organization that attached on the server machine to enable it to accomplish some special functions. Before studying this topic, students need to have an understanding of the difference between server and ordinary PC (PC) machine.

? What are the differences between PC and server:

1. PC and professional server is completely two kinds of things, hardware is different, of course, the driver can not be the same. For example, for the server board, the most important is high reliability and stability, followed by high performance. Because most servers have to meet 24 hours a day, 7 days a week full-load job requirements. Price is naturally more expensive, of course, the PC also has more than 20000 yuan configuration, such a PC can also do the server, but not the real server.

2. Due to the large amount of server data processing, it is necessary to adopt multi-CPU parallel processing structure, that is, one server installs 2, 4, 8 and other CPUs (must be an even number), for the server, multi-processor can be used for high-load high-speed applications such as database processing, and for workstations, Multi-processor systems can be used for high processing speed applications that cannot be achieved by single processors such as three-dimensional graphics and animated file encodings. To accommodate high-speed data processing tasks over long periods of time, in terms of memory, the server board can support up to more than 10 GB or even dozens of GB of memory capacity and requires high reliability.

? Web Server

The Web server is a software mechanism specifically for the HTTP protocol, we can install a Web server on a server, and then deploy our site in this Web server, so that we in the client through the browser to make some requests for this site, The Web server can receive our request and make some response to the client with a certain amount of processing. The Web server is very efficient in handling some static HTTP requests, which means it is more professional. Common Web server software has Apache and so on.

? Application Server

According to our definition, as an application server, it exposes commercial logic to client applications through various protocols, including HTTP. The Web server primarily handles sending HTML to the browser for browsing, and the application server provides access to business logic for use by client applications. The application server uses this business logic just as you would call a method of an object (or a function in a procedural language). In other words, our site also deploys executable files developed in C # or the Java language, which may be used to perform special functions or some operation on the database, when the Web server uses the application server, and the latter invokes an executable file written in a high-level language. The processed results are then converted to a language that can be returned to the client under the HTTP protocol that the Web server recognizes. Common application servers are familiar to Tomcat, JBoss, and so on.

This is not to say that the application server will not be able to resolve the HTTP protocol, of course, they have this function, I think Tomcat can fully parse the HTML file, but it is not very professional in response to static pages.

Although the application server is a comprehensive talent, we usually build the server with a comprehensive configuration of the Web server and application server, which is a good choice both in terms of efficiency and security.

Apache, Tomcat, and IIS connections

? Apache

Apache originates from the NCSAHTTPD server and has been modified many times to become one of the most popular Web server software in the world. Apache is taken from the "a patchy server" pronunciation, meaning is full of patches of the server, because it is free software, so constantly someone to develop new features, new features, modify the original flaw. Apache is characterized by simple, fast, stable performance, and can be used as a proxy server. Apache support for Linux is quite perfect. Its success lies primarily in its open source, an open development team, support for cross-platform applications (which can run on almost all UNIX, Windows, Linux system platforms), and its portability. Apache is a Web server environment program that can be used as a Web server. However, only support static Web pages, such as (asp,php,cgi,jsp) and other dynamic Web pages, it seems powerless.

? Tomcat

Tomcat is a Java-based Web application container that is open source, running Servlets, and JSP Web application software. Tomcatserver is executed according to the servlet and JSP specifications, so we can say that Tomcat server also implements the Apache-jakarta specification and is better than most commercial application servers. Tomcat is an application server, an application server that can parse the Java language Well, and of course he can parse some static web pages.

? IIS

IIS is an abbreviation for Internet informationservices and is a basic Internet service based on running MicrosoftWindows provided by Microsoft Corporation. It was originally an optional package for the Windows NT version, which was then built on Windows 2000, Windows XP Professional, and Windows Server 20,031, but was not IIS on the widely used version of Windows Xphome.

Summary

This chapter focuses on the basics of Web applications, and is designed to require students to have a clear understanding of some basic knowledge. It is also noted that the book will be explained by Tomcat as a server software.

In this chapter we should understand:

1, c/S, b/s meaning of the respective expression

2, the application server and the Web server contact

3. The history and features of Tomcat.

One of the JSPs Web application overview