Scriptlets, Expression and Declaration are scripting elements in JSP page using which we can add java code in the JSP pages.
A scriptlet tag starts with <% and ends with %>. Any code written inside the scriptlet tags go into the _jspService() method. For example;
<%
Date d = new Date();
System.out.println("Current Date="+d);
%>
Since most of the times we print dynamic data in JSP page using out.print() method, there is a shortcut to do this through JSP Expressions. JSP Expression starts with <%= and ends with %>.
<% out.print("Learning"); %> can be written using JSP Expression as <%= "Learning" %>
Notice that anything between <%= %> is sent as parameter to out.print() method. Also notice that scriptlets can contain multiple java statements and always ends with semicolon (;) but expression doesn’t end with semicolon.
JSP Declarations are used to declare member methods and variables of servlet class. JSP Declarations starts with <%! and ends with %>.
For example we can create an int variable in JSP at class level as <%! public static int count=0; %>.
