JSP (Java Server Pages) is a dynamic web page technology standard initiated by Sun Microsystems and established by many companies. JSP technology is a bit similar to ASP technology, it is in the traditional web page HTML file (. HTM, *. HTML) insert Java program segment (scriptlet) and JSP tag (tag), thus forming JSP file (. JSP). The web application developed with JSP is cross platform, which can run under Linux and other operating systems.
Brief introduction of JSP
JSP technology uses Java programming language to write XML like tags and scriptlets to encapsulate the processing logic of generating dynamic web pages. Web pages can also access the application logic of resources existing in the server through tags and scriptlets. JSP separates the logic of web page from the display of web page design, supports reusable component-based design, and makes the development of web-based applications fast and easy. JSP (Java Server Pages) is a dynamic page technology, its main purpose is to separate the presentation logic from servlet.
When the web server encounters the request to visit the JSP Web page, it first executes the program segment, and then returns the execution result together with the HTML code in the JSP file to the client. The inserted Java program segment can operate the database, reorient the web page and so on, so as to realize the functions needed to establish the dynamic web page.
JSP, like java servlet, is executed on the server side, and usually returns an HTML text to the client side, so the client side can browse as long as it has a browser.
The last version of JSP’s 1.0 specification was released in September 1999, and the 1.1 specification was released in December. At present, the relatively new one is JSP 1.2 specification, and the draft for comments of JSP 2.0 specification has been published. JSP page consists of HTML code and embedded Java code. The server processes the Java code after the page is requested by the client, and then returns the generated HTML page to the browser of the client. Java servlet is the technical basis of JSP, and the development of large web applications needs the cooperation of java servlet and JSP. JSP has all the characteristics of Java technology, such as easy to use, complete object-oriented, platform independent, safe and reliable, mainly facing the Internet.
Since the launch of JSP, many large companies support JSP technology server, such as IBM, Oracle, BEA company, so JSP quickly become the server-side language of commercial applications.
JSP can be expressed as a simple equation: HTML + java + JSP tag = JSP.
The strength of JSP technology
(1) Write once, run everywhere. The code doesn’t need to be changed except for the system.
(2) Multi platform support of the system. Basically, it can be developed in any environment on all platforms, deployed in any environment, and expanded in any environment. comparison ASP.NET The limitations of JSP are obvious.
(3) Powerful scalability. Java has shown great vitality, from running servlet / JSP with only one small jar file, to clustering and load balancing with multiple servers, to transaction processing and message processing with multiple applications, and from one server to countless servers.
(4) Diversified and powerful development tool support. This is very similar to ASP, Java has many excellent development tools, and many of them are free, and many of them can run smoothly on a variety of platforms.
(5) Support server-side components. Web applications need powerful server-side components to support. Developers need to use other tools to design and implement complex functional components for web pages to enhance system performance. JSP can use mature Java beans components to achieve complex business functions.
The weakness of JSP technology
(1) like ASP, some advantages of Java are its fatal problems. It is for cross platform functions and extreme scalability that the complexity of products is greatly increased.
(2) the running speed of Java is achieved by using class resident memory, so the memory it uses in some cases is indeed the “lowest cost performance ratio” compared with the number of users. On the other hand, it also needs hard disk space to store a series of. Java files and. Class files, as well as the corresponding version files.