Work week Four

since I recently in a job management system, some of which use JSP technology, but I feel that everyone is not very understanding of JSP technology, so today and everyone to share my simple understanding of JSP technology.

JSPThe full name is Java Server pages, which is simply a simplified servlet design, a dynamic Web technology standard developed by Sun Microsystems, a company that many companies are involved in. JSP technology is a bit like ASP technology, it is in the traditional Web page HTML (standard Common Markup Language subset) file (*.htm,*.html) inserted Java program segment (scriptlet) and JSP tag (tag), thereby forming a JSP file, suffix named (*.jsp). Web applications developed with JSP are cross-platform and can run on Linux and other operating systems.
It implements the Java extension in HTML syntax (in <%,%> form). JSP, like a servlet, is executed on the server side. Usually returned to the client is an HTML text, so the client can browse as long as there is a browser.
JSP technology uses the Java programming language to write tags and scriptlets of class XML to encapsulate the processing logic that produces dynamic Web pages. Web pages can also access the application logic of resources that exist on the server through tags and scriptlets. JSP separates the Web page logic from the display of the web design, supports reusable component-based design, and makes the development of Web-based applications quick and easy. JSP (JavaServer pages) is a dynamic page technology whose main purpose is to separate the presentation logic from the servlet.
Java servlet is the technical foundation of JSP, and the development of a large Web application requires Java servlet and JSP mates to complete. JSP has the simple and easy-to-use Java technology, completely object-oriented, platform-independent and safe and reliable, mainly for the internet all the characteristics.
Its basic feature is the ability to defer the evaluation of JSP tag properties for containers that process JSPs. We know that the general JSP is the first to evaluate the properties of the JSP tag, and then use these properties when working with JSP tags, while JSP fragment provides dynamic properties. In other words, these properties can be changed when the JSP processes its markup body. The JSP needs to define such a property as the Javax.servlet.jsp.tagext.JspFragment type. When the JSP tag is set to this form, the markup attribute is actually handled in a similar way to the tag body. In a program that implements markup, the tag attribute can be evaluated repeatedly. This usage is called JSP fragment. JSP fragment can also define a homemade tag action that is used in a simpletag handler. As illustrated in the previous example, Getjspbody returns a Jspfragment object and can be used multiple times in the Dotag method. It is important to note that JSPs using JSP fragment can only have generic text and JSP action, and cannot have scriptlet and scriptlet expressions.
　 Advantages
(1) Once written, run everywhere. The code does not have to make any changes other than the system.
(2) Multi-platform support for the system. It can be developed in virtually any environment on all platforms, deployed in any environment, and expanded in any environment. The advantages of JSP compared to the limitations of ASP are obvious.
(3) Strong scalability. From only a small jar file can run servlet/jsp, to multiple servers for cluster and load balancing, to multiple application for transaction processing, message processing, a server to countless servers, Java shows a huge vitality.
(4) Diversified and powerful development tools support. This is like ASP, Java has a lot of very good development tools, and many can be free, and many of them have been able to run smoothly under a variety of platforms.
(5) Support server-side components. Web applications require powerful server-side components to support, and developers need to leverage other tools to design components that implement complex functionality for Web page calls to enhance system performance. JSP can use mature Java BEANS components to implement complex business functions.
　　 Disadvantages
(1) As with ASP, some of Java's advantages are its deadly problem. It is due to the function of cross-platform, in order to extreme scalability, so greatly increased the complexity of the product.
(2) The speed of Java is done with the class resident memory, so it is in some cases used in memory than the number of users is indeed the "lowest performance price ratio".

Work week Four