Cheat sheet - the three JSP scripting elements

Slide 2 — the scripting elements provide the ability to insert java code inside a JSP. There are exactly three of them.

Element	Syntax	Becomes	Use it for
Scriptlet `<% %>`	`<% java code %>`	statements inside `_jspService()`	loops, conditions, local variables, `request.getParameter()`, anything that needs `out.print()`
Expression `<%= %>`	`<%= statement %>`	`out.print(statement)`	printing one value; no `out.print()` needed, no semicolon allowed
Declaration `<%! %>`	`<%! field or method %>`	a field or method of the servlet class, outside `_jspService()`	helper methods, constants. Almost never for state — use a scope instead

Directive	Syntax	Purpose
`page`	`<%@ page attribute="value" %>`	attributes that apply to the whole page: import, contentType, pageEncoding, buffer, info, errorPage, isErrorPage, isELIgnored …
`include`	`<%@ include file="resourceName" %>`	paste a static resource into this page at translation time
`taglib`	`<%@ taglib uri="uriOfTagLibrary" prefix="prefix" %>`	declare a tag library so its tags may be used (see Session 3 and Session 5)

Cheat sheet — the three scripting elements