<s1 title="Servlet Applications">

<summarylist/>

<s2 title='Introduction'>

<p>An application collects servlets, JSP pages, scripts and Java Beans into a
self-contained web application.  Applications are just generalized virtual
hosts, only based on the URL instead of the host name.</p>

<p>For example, a
bulletin board application groups pages for article reading, group
listing, user registration, and new article posting into a single
application.</p>

<p>Applications can keep track of user sessions, giving the users the
illusion of a single application out of disjoint pages.</p>

<ul>
<li>Resin organizes applications with an application <a
href='#dir'>directory</a>, WEB-INF
<li><a href='#session'>Sessions</a> share state for a user's visit to
the site.
</ul>

<p>Many, if not most sites, will only use the default application.</p>

</s2>

<s2 name='dir' title='Applications'>

<deftable title='application contents'>
<tr><th>File/Directory</th><th>Contents</th></tr>
<tr><td>.</td><td>JSP, HTML and GIF files</td></tr>
<tr><td>WEB-INF/classes</td><td>Java class files</td></tr>
<tr><td>WEB-INF/lib</td><td>Java jars</td></tr>
<tr><td>WEB-INF/tmp</td><td>Temporary servlet files</td></tr>
<tr><td>WEB-INF/work</td><td>Generated java for JSP and XSL</td></tr>
</deftable>

<ul class=none>
<li><ct:img src='folder.gif'/>&nbsp;example
<ul class=none>
  <li><ct:img src='file.gif'/>&nbsp;index.html
  <li><ct:img src='file.gif'/>&nbsp;folder.gif
  <li><ct:img src='file.gif'/>&nbsp;article.gif
  <li><ct:img src='jsp.gif'/>&nbsp;post-article.xtp
  <li><ct:img src='folder.gif'/>&nbsp;jsp-interest
  <ul class=none>
    <li><ct:img src='jsp.gif'/>&nbsp;index.jsp
    <li><ct:img src='jsp.gif'/>&nbsp;article1.jsp
    <li><ct:img src='jsp.gif'/>&nbsp;article2.jsp
  </ul>
  <li><ct:img src='folder.gif'/>&nbsp;WEB-INF
  <ul class=none>
    <li><ct:img src='folder.gif'/>&nbsp;lib
    <ul class=none>
      <li><ct:img src='bean.gif'/>&nbsp;bulletin-board.jar
    </ul>
    <li><ct:img src='folder.gif'/>&nbsp;classes
    <ul class=none>
      <li><ct:img src='bean.gif'/>&nbsp;Navigation.class
      <li><ct:img src='bean.gif'/>&nbsp;HelloWorld.class
    </ul>
    <li><ct:img src='folder.gif'/>&nbsp;xsl
    <ul class=none>
      <li><ct:img src='style.gif'/>&nbsp;default.xsl
      <li><ct:img src='style.gif'/>&nbsp;article.xsl
    </ul>
  </ul>
</ul>
</ul>

</s2>

<s2 name=beans title='JSP Beans'>
<p>Java Beans get first class treatment in JSP 1.0.  Beans can be
created for a page, across a session, or for the entire application.</p>

<p>The classes and lib directories can contain application beans used by <a
href='jsp-actions.xtp#usebean'>jsp:useBean</a>.  These are simply Java
classes implementing the bitmechanic work of an application.</p>

<p>For example, a shopping cart application may have a set of Java
classes that perform the security necessary for credit card
processing.  The application can put those classes in the beans
directory and access them from the JSP page.</p>

<p>Beans can be created with different lifetimes.</p>
<ul>
<li>Application beans last the lifetime of an application.
<li>Session beans last for a user's session.
<li>Request beans last for a single request.
<li>Page beans only last for a single page.
</ul>

<p>Requests and pages often last the same lifetime, but may differ if one
page <a href='jsp-actions.xtp#forward'>forwards</a> or <a
href='jsp-actions.xtp#include'>includes</a> another page. </p>

<s3 title='Accessing Beans'>
<p>Each bean is defined with a <a href='jsp.xtp#usebean'>jsp:useBean</a>
directive.</p>

<p>JSP assigns the created bean object to the JavaScript variable
named by jsp:useBean.</p>

<p>In addition, the created beans are stored in JSP variables: page
beans are stored in <code/request/>, session beans are stored in
<code/session/>, and application beans are stored in
<code/application/>.  Storing the beans in the JSP variables lets
other beans and functions retrieve the beans.</p>

<example title='Beans in variables: test.jsp'>
&lt;jsp:useBean id='test' class='java.util.Hashtable'&gt;

&lt% test.put("a", 1); %&gt;
&lt%= test.get("a"); %&gt;
</example>

<example title='Page beans in request: test.jsp'>
&lt;jsp:useBean id='test' class='java.util.Hashtable'&gt;

&lt;% 
  var t = request.attributes.test
  t.put("a", 1);
%&gt;
&lt%= test.get("a"); %&gt;
</example>
<results>
1
</results>

</s3>

</s2>

<s2 name=session title='Sessions'>
<p>Session variables let applications keep track of the user as she moves
through the site.  Any e-commerce site needs this capability to keep
track of the user's purchases.</p>

<p>JSP sessions start when the page accesses the <a
href='jsp-variables.xtp#session'>session</a> variable.</p>

<p>Sessions end when the session times out, when the session is
invalidated, or when the application ends.</p>
</s2>
</s1>
