Random ruminations of a java developer

Thursday, August 24, 2006

Quick JSP (Java Server Pages) Programming Tutorial

This is a quick tutorial of the JSP technique. JSP pages are used with Java application servers, for example Tomcat, Weblogic or Websphere.

Some quick facts before we get going into more details:

-JSP files are executed at server.
-JSP files contain HTML + varying amounts of embedded Java code. (There's a bit more though, like tags and EL, but you can ignore them when beginning)
-When a web user surfs to an address like http://foo.com/index.jsp, this jsp page is executed at the server, and the result is a normal HTML page for the client browser.

Very easy so far?

JSP has two styles of embedding Java code into JSP:

1) Java expression:

..html...
<%= java expression %>
..html..

This first style is used when you want to output the result of a simple java expression into the resulting HTML. For example:

<div>
<%= customer.getName() %>
</div>

Notice that there is no semicolon (;) here.

2) A block of Java code:

...html...
<% // java code %>
...html...

This style is used when you want to execute larger blocks of code. For example:

<p>
<%
Customer customer = new Customer();
customer.setName( "customername" );
%>
</p>

Importing classes

The import is a bit different from normal Java imports. It goes like this:

<%@ page import="java.util.List,
java.util.Iterator"
%>

Which functions in identical way to this java class import declaration:

import java.util.List;
import java.util.Iterator;

The JSP import declaration should be in the beginning of the page, just like a normal Java import.

Outputting strings to resulting html from code blocks

This is easy:

<%
...java code...
out.println( "foo" );
...java code...
%>

Thats it , now you are ready to code JSP pages. There is more stuff, but this will get you started with producing real results.

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