![9
Expression
A shortcut to print out a value or an
expression
<%= [expression]%>
Expression can be a variable, formula, object
property, string concatenation, method with
return value, or anything that returns a value
See example “expression-example.jsp”](https://image.slidesharecdn.com/9c4djsp-140809031853-phpapp01/85/JSP-Processing-9-320.jpg)
JSP Processing
- 1. JSP Processing 1 Submitted by - Sadhana Singh Shri Ram Murti Smarak College of Engg. & Tech.
- 2. 2 JSP Pages JSP page file ends with “.jsp” by default JSP pages are organized like any other HTML files using the normal directory/file structure A JSP page is usually composed of regular HTML tags and JSP scripting elements JSP page is implicitly compiled to servlet class and loaded into memory when the page is requested the first time after creation, or when the page is requested the first time after modification Refer to table 10.1 in the textbook and the next slide
- 3. Model-View-Controller A Design Pattern Controller -- receives user interface input, updates data model Model -- represents state of the world (e.g. shopping cart) View -- looks at model and generates an appropriate user interface to present the data and allow for further input 3
- 6. 6 JSP Compilation and Execution JSP Page Compile JSP Servlet Instance in Memory init() service() First request after creation or modification Subsequent Requests (can be from different users and sessions) JSP Servlet Automatic Compilation
- 7. 7 JSP Elements Scripting elements Scriptlet Regular Java code Expression Shortcut for output Declaration Declaring variables and methods at the class level Directive JSP action Comments (<%-- … --%>)
- 8. 8 Scriptlets Wraps regular Java statements which are usually written within a method <% … (Java statements) // may include comments, variable declaration and assignment, loops, conditional statements, object initialization, method call, etc… %> Using the implicit object “out” as the standard output out.println( … ) or out.print( … ) See example “scriptlet-example.jsp”
- 9. 9 Expression A shortcut to print out a value or an expression <%= [expression]%> Expression can be a variable, formula, object property, string concatenation, method with return value, or anything that returns a value See example “expression-example.jsp”
- 10. 10 Declarations Declaration element is used to define member variables and methods <%! … %> Variables not defined in declaration element are local / method level variables Methods can only be defined in the declaration element Like regular class variables and methods, the location where you define these variables and methods is not important See example “declaration.jsp”
- 11. 11 JSP Page Directive Directives affects the overall structure of the servlet generated <%@ … %> Use page directive to import classes <%@ page import=“…, …, …”%> This is equivalent to the “import” statement in regular Java classes