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<?xml version="1.0"?>
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to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
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Unless required by applicable law or agreed to in writing,
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"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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under the License.
-->
<document>
<properties>
<title>Overview</title>
<projectfile>xdocs/project.xml</projectfile>
<subprojectfile>xdocs/struts.project.xml</subprojectfile>
</properties>
<body>
<section name="Overview">
<p>The VelocityStruts sub-project integrates Velocity with the
<a href="http://struts.apache.org/">Apache Struts</a>
web application framework and enables the use of Velocity templates
interchangeably with JSP pages for the view layer.</p>
<p>Various other
<a href="http://wiki.apache.org/velocity/PoweredByVelocity">web application frameworks</a>
offer built-in support for Velocity templates. This project
provides the minimal glue necessary to give Struts developers
an alternative to JSP. </p>
<p><img src="images/velstruts_diag1.png" border="0"/></p>
<p><strong>Diagram 1.</strong> Comparison of JSP and Velocity for
the view layer in a Struts application.</p>
<p>As we follow the typical Struts process flow in Diagram 1,
notice how there is relatively little change except for the addition
of Velocity. The velocity-struts.jar leverages a standalone Velocity
servlet to process template files (specifically, the jar file is
velocity-tools-x.x.jar) and uses some drop-in tools to provide
transparent access to Struts specific objects (ex. message resources,
form beans, errors, links). The action mapping file will simply contain
ActionForwards that send control to a Velocity-based View layer instead
of sending to a JSP. </p>
<p>Also notable is that Velocity and JSP are <strong>not</strong>
mutually exclusive. Both technologies can be used in the same
application without any problems. This allows developers the option
of trying Velocity without heavy modification to existing applications.</p>
<p>We're convinced that once you give Velocity a try, you'll really like it.</p>
</section>
<section name="Default Configuration">
<p>
VelocityStruts includes both the <a href="generic.html">
GenericTools</a> and <a href="view.html">VelocityView</a> and
adds tools for use in Struts 1.x applications. These tools match
the functions of the key Struts taglibs and provide access to
Struts resources, messages, tiles, validation functions and more.
</p>
<p>
The default configuration provided for
<a href="struts.html">VelocityStruts</a> is
<a href="http://svn.apache.org/viewvc/velocity/tools/trunk/src/main/java/org/apache/velocity/tools/generic/tools.xml?view=markup">
here</a> and
<a href="http://svn.apache.org/viewvc/velocity/tools/trunk/src/main/java/org/apache/velocity/tools/view/tools.xml?view=markup">
here</a> and
<a href="http://svn.apache.org/viewvc/velocity/tools/trunk/src/main/java/org/apache/velocity/tools/struts/tools.xml?view=markup">
here</a>.
</p>
</section>
<section name="Dependencies">
<p>
The dependencies required for VelocityStruts can be found on our
<a href="dependencies.html#VelocityStruts">dependencies chart</a>.
</p>
</section>
<section name="Tools">
<p>
These are in addition to tools provided by
<a href="generic.html#Tools">GenericTools</a>
and
<a href="view.html#Tools">VelocityView</a>.
</p>
<ul>
<li>
<javadoc package="struts" name="ActionMessagesTool"/>
- For accessing/displaying Struts action messages.
</li>
<li>
<a href="javadoc/org/apache/velocity/tools/struts/ErrorsTool.java ">ErrorsTool</a>
- For accessing/displaying Struts error messages.
</li>
<li>
<javadoc package="struts" name="FormTool"/>
- For working with HTML forms in Struts apps.
</li>
<li>
<javadoc package="struts" name="MessageResourcesTool"/>
- Abstract view tool that provides access to Struts
message resources.
</li>
<li>
<javadoc package="struts" name="MessageTool"/>
- Provides methods to render Struts application resources
(for i18n and other textual content access).
</li>
<li>
<javadoc package="struts" name="SecureLinkTool"/>
- For using Struts SSL Extensions. It has the same
interface as
<javadoc package="struts" name="StrutsLinkTool"/>
and can function as a substitute if Struts 1.x
and SSL Ext are installed.
</li>
<li>
<javadoc package="struts" name="StrutsLinkTool"/>
- Subclass of
<javadoc package="view" name="LinkTool"/>
for creating URI links in Struts by adding support
for Struts actions and forwards.
</li>
<li>
<javadoc package="struts" name="TilesTool"/>
- For using Struts-Tiles (not for Tiles 2!)
in Velocity.
</li>
<li>
<javadoc package="struts" name="ValidatorTool"/>
- Uses Struts-Validator to produce client side
javascript validation for your forms.
</li>
</ul>
</section>
<section name="Examples">
<p>A Struts application example has been included to demonstrate the use
of the VelocityViewServlet with the automatically loaded VelocityStruts tools.</p>
<p>To run the examples you need Tomcat 4+ or a compatible servlet runner.</p>
<p>The 'ant examples' target of the build process automatically generates
a ready-to-deploy <b>struts.war</b>
archive file located in the examples subdirectory of the distribution.
Deploy (i.e. copy) one or both of these war files to the webapps directory
of your servlet runner and restart.
Now point a web browser at the following url:</p>
<p><b>http://<your_server>:<port>/struts/</b></p>
<p>VelocityStruts is also distributed with
<a href="view.html#Examples">a couple other examples</a> that use
VelocityTools without the Struts 1 tools.</p>
</section>
<section name="Benefits">
<p>There are many different reasons why people are choosing Velocity
technology for the view layer. Here are some:</p>
<p>
<ul>
<li>Velocity helps enforce a clean separation between the view
layer and the model/control layers. This leads to clean application
design and a clear separation of concerns between View Designers
and back-end Developers.</li>
<li><a href="http://velocity.apache.org/engine/devel/vtl-reference-guide.html">Velocity Template Language (VTL)</a>
has few directives and is simple and easy to learn. Most
people report being productive within a day.</li>
<li>Velocity is easy to extend with <i>Tools</i> which are simply
any class which has public methods. These are typically much cleaner
and easier to develop than JSP custom tag libraries.</li>
<li>Using the TilesTool it is easy
to mix Velocity and JSP tiles in the same page/layout. For those
using Tiles, this makes gradual migration between or integration of
the two view technologies trivially easy!</li>
<li>Velocity 'macros' are a powerful tool for the View Designer.
They enable the creation of reusable snippets of markup, often
eliminating what would have been a need to develop a custom tag
library or other server-side tool.</li>
<li>Velocity templates are <strong>not</strong> limited to HTML
and can be used to produce any type of text output including XML,
SQL, ASCII, PostScript, etc.</li>
<li>Velocity enables easy access to dynamic data
that Web Designers can understand.</li>
<li>Velocity being interpreted, enables a simple development cycle
where template errors can quickly be localized and debugged.</li>
<li>Velocity, which caches templates for speed, has been reported
to have performance comparable or better than JSP.</li>
<li>Velocity is <strong>supported</strong> by an active and helpful
community of users and developers.</li>
</ul>
</p>
</section>
<section name="Success Stories">
<p>Comments from folks who are using Struts and Velocity:</p>
<p>
<blockquote>
<p>"<i>We've been using Struts/Velocity for some time now and we find it to be
an extremely well matched combination. One of the main advantages of
Velocity is that the syntax is incredibly easy. I can explain it to a
designer who has never seen it before and expect them to be useful
within an hour.</i>" </p>
<p>"<i>One of the nicest things it enforces is the separation of presentation
layer and business logic. It removes the desire to 'fix' problems by
just putting a small change into the JSP via scriptlets. It also makes
the code a <strong>lot</strong> more readable which also reduces the
development time.</i>"</p>
<p>"<i>Struts is a solid framework and Velocity makes it
even better.</i>"</p>
<p>"<i>I find that the VelocityTools for Struts works as well, or better, with
Struts than another other presentation technology, bar none. In fact,
most of the tools work just as well with any other framework you might
care to name.</i>"
--<a href="http://marc.theaimsgroup.com/?l=velocity-user&m=106520662105461&w=25">Ted Husted</a>
(author of <a href="http://husted.com/struts/book.html">Struts in Action</a>)</p>
</blockquote>
</p>
</section>
<section name="License">
<p>This software is licensed under the
<a href="http://velocity.apache.org/engine/devel/license.html">Apache Software License 2.0</a></p>
</section>
</body>
</document>
|
