INTERACTIVE WEB SERVICES WITH JAVA

JSP Pages

JSP:

developed as response to ASP and PHP
HTML (or XML) templates
embedded Java code generates HTML dynamically
user-defined tags referring to Java code that generates HTML dynamically
= Servlets inside-out (JSP pages are translated into Servlets)
all Servlet features are direcly available

Another Hello-World example:
<% response.addDateHeader("Expires", 0); %> <html><head><title>JSP</title></head> <body><h1>Hello World!</h1> <%! private int hits = 0; %> You are visitor number <% synchronized(this) { out.println(++hits); } %> since the last time the service was restarted. <p> This page was last updated: <%= new java.util.Date().toLocaleString() %> </body></html>

Note that only an expert Java programmer could write this:

java.util.Date() implements toLocaleString()
synchronized(this) { .. } is necessary

Inserting code in XML templates:

Expressions: <%= expression %>
Statements: <% statement %>
Declarations: <%! declaration %>
JSP directives: <%@ directive %>

Alternative XML syntax:

<jsp:expression>...</jsp:expression>
<jsp:scriptlet>...</jsp:scriptlet>
<jsp:declaration>...</jsp:declaration>
<jsp:directive.../>
(<jsp:include.../>)

Pre-declared variables:

HttpServletRequest request
HttpServletResponse response
HttpSession session
JspWriter out
ServletContext application
ServletConfig config
PageContext pageContext

Directives:

include
page
taglib