JSP Elements

Scriptlet: Everything between <% and %> is a Scriptlet, which is just plain old java. Scriptlet’s can have variable declarations. But they are local variables.

Syntax: Scriptlet doesn’t add any additional character.

<% out.println(“Hi”); %>

Directive: A directive is a way for you to give special instructions to the container at the page translation time.

Syntax: Directive adds an additional character to the start of the element – the @ sign.

<%@ page import = ”java.util.*” %>

Expression: Expressions becomes the argument to out.print()

Syntax: Expression adds an additional character to the start of the element – an equal sign (=). Semicolon should be avoided at the end of the statement. No variable declarations are allowed.

<%= 50 %> Valid

<%= 50; %> Invalid (Semicolon not allowed)

<%= int i=5 %> Invalid (variable declaration not allowed)

Example:

<%= “Plus” %>

out.print(“Plus”);

NOTE:

All Scriptlet and expression code lands in a service method.

That means variables declared in a Scriptlet are always local variables.

Declaration: JSP declarations are for declaring instance members of the generated servlet class. That means both variables and methods.

Syntax: Declaration adds an additional character to the start of the element – an exclamation sign (!).

<%! int count = 0; %>