Google Git
Sign in
apache / click / b18565529fad61d895fcb4ba884206a1c93f77f1 / . / documentation / docs / faq.html
blob: c43408091494ae9a6096fe7bbd1459eb5bfc5bf1 [file] [log] [blame]
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<!--
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements. See the NOTICE file
distributed with this work for additional information
regarding copyright ownership. The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied. See the License for the
specific language governing permissions and limitations
under the License.
-->
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"/>
<meta name="Author" content="Malcolm Edgar"/>
<meta name="description" lang="en" content="Apache Click Java web application framework"/>
<meta name="keywords" lang="en" content="Apache Click, Click Framework, Java, JEE, J2EE, web application framework, open source"/>
<title>Apache Click</title>
<link rel="stylesheet" type="text/css" href="../help.css"/>
<link rel="stylesheet" type="text/css" href="../syntax-highlighter.css"/>
<style type="text/css">
dt { margin-top:2em; }
dd { margin:1em; margin-left:2em; }
</style>
<script type="text/javascript" src="../syntax-highlighter.js"></script>
</head>
<body onload="prettyPrint();">
<h1>Frequently Asked Questions</h1>
<ol>
<li><a href="#getting-help">How to get help?</a>
</li>
<li><a href="#commercial-support">What about Commercial Support?</a>
</li>
<li><a href="#tool-support">What development tools are there?</a>
</li>
<li><a href="#html-control">How can the GUI designer define the HTML if Click Controls generates everything?</a>
</li>
<li><a href="#customize-look-and-feel">How can I customize a control's look and feel (Stylesheet, JavaScript and other resources)?</a>
</li>
<li><a href="#shared-template">How can I have many Pages using the same HTML template?</a>
</li>
<li><a href="#listener-returns">Why do control listener methods have to return a boolean value?</a>
</li>
<li><a href="#exclude-fields">Can you exclude some fields from a Form?</a>
</li>
<li><a href="#localization">How do you internationalize Pages and Controls?</a>
</li>
<li><a href="#utf8-encoding">How do you encode Pages in the UTF-8 character set?</a>
</li>
<li><a href="#charset">How do you specify the character set which is used in your application?</a>
</li>
<li><a href="#multiple-posts">How can you prevent multiple form posts?</a>
</li>
<li><a href="#html-pages">How can I use *.html Click pages?</a>
</li>
<li><a href="#alternative-extension">Can Click be mapped to an extension other than *.htm?</a>
</li>
<li><a href="#cayenne-integration">What JARs should I use with Click and Cayenne?</a>
</li>
<li><a href="#spring-integration">How can you integrate Click into Spring?</a>
</li>
<li><a href="#jsp-support">Does Click support JSP?</a>
</li>
<li><a href="#pdf-and-excel-rendering">How can I render PDF and Excel documents?</a>
</li>
<li><a href="#performance">What is the performance of Click?</a>
</li>
<li><a href="#unit-testing">How do I unit test Click pages?</a>
</li>
<li><a href="#logging">Why doesn't Click use Commons Logging / Log4J for logging?</a>
</li>
<li><a href="#why-velocity">Why doesn't Click use FreeMarker as the default rendering engine?</a>
</li>
<li><a href="#why-click">Why develop a new Web Application Framework?</a>
</li>
</ol>
<p>&nbsp;</p>
<dl>
<a name="getting-help" class="heading"></a>
<dt><b>1.&nbsp; How to get help?</b></dt>
<dd>
OK you have read the documentation and reviewed the
<a href="examples.html">Examples</a> applications, but there is still something
you still don't understand. What do you do?
<p/>
You go to the click-user or click-development mail
<a href="click-online.html#mailing-lists">news groups</a>.
<p/>
This is where you get support from in open source projects. Its free, friendly
and usually pretty responsive.
<p/>
These news groups are where other people ask questions, and where users
and developers discuss ideas. Its highly recommended, so don't be shy.
<p/>
To sign up to these mail groups follow the instructions at the following links:
<ul>
<li><a href="click-online.html#user-mailing-list">click-user</a> - for Click usage discussions and help</li>
<li><a href="click-online.html#development-mailing-list">click-development</a> - for Click framework development discussions</li>
</ul>
</dd>
<a name="commercial-support" class="heading"></a>
<dt><b>2.&nbsp; What about Commercial Support?</b></dt>
<dd>
If you want commercial support or training for Click, you can obtain this
from
<a target="_blank" href="http://www.avoka.com">Avoka Technologies</a>.
<p/>
For more details please email <a href="mailto:medgar@avoka.com">Malcolm Edgar</a>.
</dd>
<a name="tool-support" class="heading"></a>
<dt><b>3.&nbsp; What development tools are there?</b></dt>
<dd>
Recommended Click development tools include:
<p/>
<ul>
<li>
<a href="click-ide.html">ClickIDE</a>
<p/>
ClickIDE is an Eclipse Web Tools Project (<a target="blank" class="external" href="http://www.eclipse.org/webtools/">WTP</a>)
plugin developed by Naoki Takezoe.
<p/>
To use the ClickIDE plugin, create a "Dynamic Web Project" and select the
"Click" Project Faclet.
<p/>
<img src="../images/clickide_config_editor_1.png"/>
<br/>
</li>
<li>
<a target="blank" class="external" href="https://nbclick.dev.java.net/">NBClick</a>
<p/>
NetBeans plug-in for Click is under development by Geertjan Wielenga and Ahmed Mohombe.
</li>
<li>
<a target="blank" class="external" href="http://velocitywebedit.sourceforge.net">Velocitywebedit</a>
<p/>
Velocitywebedit is a Velocity and HTML Editor plugin for Eclipse.
<p/>
<img src="../images/velwebedit.png"/>
<p/>
After installing Velocity Web Edit configure Eclipe *.htm file associations
to use Velocity Editor. Do this via the Eclipse menus:
Window &gt; Preferences &gt; General &gt; File Associations
</li>
<li>
<a target="blank" class="external" href="http://propsorter.sourceforge.net">Veloeclipse</a> &nbsp; - &nbsp;
Velocity and HTML Editor plugin for Eclipse
</li>
<li>
<a target="blank" class="external" href="http://veloedit.sourceforge.net">Veloedit</a> &nbsp; - &nbsp;
Velocity and HTML Editor plugin for Eclipse
</li>
</ul>
</dd>
<a name="html-control" class="heading"></a>
<dt><b>4.&nbsp; How can the GUI designer define the HTML if Click Controls generates everything?</b></dt>
<dd>
In Click there is nothing preventing you from laying out HTML forms by hand.
It just provides the option of doing it automatically for you.
<p/>
There are a number of approaches you can use for generating for HTML,
each with pros &amp; cons:
<p/>
<ol>
<li>
<u>Use Click forms and controls to do all the HTML rendering for you.</u>
<p/>
This a 80/20 approach where you can quickly get stuff developed, but it may
not meet all your UI style requirements.
<p/>
Please note the Forms control provides many
<a href="click-api/org/apache/click/control/Form.html#auto-layout">auto layout</a>
options, see the <a href="examples.html">click-examples</a> 'Form Properties'
for a demonstration.
<p/>
The Form control also renders the class attributes 'form', 'fields', 'errors' and 'buttons'
in the form's HTML elements enabling fine grained CSS control.
<p/>
As an example you could configure a form to display the labels on top, and want to
increase the vertical spacing between fields. To do this simply define the CSS
style in front of your form:
<pre class="codeHtml">
&lt;style type="<span class="st">text/css</span>"&gt;
td.<span class="kw">fields</span> { padding-top: 0.75em; }
&lt;/style&gt;
<span class="red">$</span><span class="blue">form</span> </pre>
Fields are also rendered with an 'id' attribute enabling manipulation of individual fields.
<p/>
</li><li>
<u>Subclass Click Form/Controls to customise HTML rendering.</u>
<p/>
This is a good approach for ensuring a common LAF across your web application,
but you will have to get your hands dirty and write some code.
</li><li>
<u>Use Panel to class to create reusable HTML blocks.</u>
<p/>
The
<a href="click-api/org/apache/click/control/Panel.html">Panel</a>
control support custom Velocity templates, which is an ideal way
to create reusable HTML sections which you can include in many pages.
Panels also support nested controls, enabling your sections to support
control based behaviour.
</li><li>
<u>Use Velocity macros for a generic HTML layout.</u>
<p/>
This is easy to do and gives you good reuse across your web application.
<p/>
Please see the Form
<a href="click-api/org/apache/click/control/Form.html#velocity-macros">velocity macros</a>
example, and also see the <a href="examples.html">click-examples</a> 'Velocity Macro'
demonstration.
</li><li>
<u>Layout your HTML forms by hand.</u>
<p/>
This gives you the ultimate control in presentation, but provides no reuse
across your web application.
<p/>
Please see the Form
<a href="click-api/org/apache/click/control/Form.html#manual-layout">manual layout</a>
example.
</li>
</ol>
</dd>
<a name="customize-look-and-feel" class="heading"></a>
<dt><b>5.&nbsp; How can I customize a control's look and feel (Stylesheet, JavaScript and other resources)?</b></dt>
<dd>
See the section <a href="configuration.html#auto-deployed-files">aut deployed files</a>
for details on how to customize and override a control's resources.
</dd>
<a name="shared-template" class="heading"></a>
<dt><b>6.&nbsp; How can I have many Pages using the same HTML template?</b></dt>
<dd>
To do this use the Page templating technique detailed in the
<a href="pages.html#page-templating">Page Templating</a> topic.
<p/>
Page templating is highly recommended for your web applications, as it provides
numerous benefits including:
<ul>
<li>greatly reduces the amount of HTML you need to maintain</li>
<li>ensures you have a common look and feel across you application</li>
<li>makes your application more robust, as there is less code to test</li>
</ul>
For a live demonstration of page templating deploy and run the
<a href="examples.html">click-examples</a> application.
</dd>
<a name="listener-returns" class="heading"></a>
<dt><b>7.&nbsp; Why do control listeners methods have to return a boolean value?</b></dt>
<dd>
Control listener methods have to return a boolean value to state whether the
Pages controls and methods should continue to be processed. To continue
processing listener methods should return true, to abort they should return false.
<p/>
The reason you may want to abort further processing is so you can navigate
directly to another page, rather than continuing to execute other control or
page methods which may be time consuming. You can use this feature like a break
or goto statement. For example:
<pre class="codeJava">
<span class="kw">public boolean</span> onLogoutClick() {
setRedirect(Logout.<span class="kw">class</span>);
<span class="kw">return false</span>;
}
</pre>
Please see the Page <a href="pages.html#page-navigation">Navigation</a> topic
for more details.
</dd>
<a name="exclude-fields" class="heading"></a>
<dt><b>8.&nbsp; Can you exclude some fields from a Form?</b></dt>
<dd>
To exclude some fields from being displayed in a shared Form class use the
<a href="click-api/org/apache/click/control/Form.html#removeFields(java.util.List)">Form.removeFields()</a>
method.
<p/>
You can even do this in your page template. Just make sure you call you call
it before $form renders itself. For example:
<pre class="codeHtml">
<span class="red">$</span><span class="blue">form</span>.<span class="blue">removeFields</span>(["field11", "field15", "field22"])
<span class="red">$</span><span class="blue">form</span>
</pre>
</dd>
<a name="localization" class="heading"></a>
<dt><b>9.&nbsp; How do you internationalize Pages and Controls?</b></dt>
<dd>
Click provides good support for application localization and
internationalization (I18N) requirements.
<h4>Page Messages</h4>
The Page class supports page specific string localisation bundles using the
method
<a href="click-api/org/apache/click/Page.html#getMessage(java.lang.String)">getMessage(String)</a>.
For example a Login class with three locale string property files on the classpath:
<pre class="codeConfig">
/com/mycorp/pages/Login.properties
/com/mycorp/pages/Login_en.properties
/com/mycorp/pages/Login_fr.properties </pre>
In your Login Page class you can use the <tt>getMessage()</tt> method
to lookup request localized message strings.
<pre class="codeJava">
<span class="kw">public void</span> onInit() {
addModel(<span class="st">"title"</span>, getMessage(<span class="st">"title"</span>));
} </pre>
In your HTML page template you can also access the localize message using
the <a href="click-api/org/apache/click/util/MessagesMap.html">MessagesMap</a>
object which is added to the template using the name "messages". For example:
<pre class="codeHtml">
&lt;h2&gt;<span class="red">$</span><span class="blue">messages.title</span>&lt;/h2&gt; </pre>
You can also define Field and ActionLink labels and title values in your pages
properties file using control name lookup convention. For details please see
the Javadoc:
<ul style="margin-top:1em;">
<li>
<a href="click-api/org/apache/click/control/ActionLink.html#getLabel()">ActionLink.getLabel()</a>
</li>
<li>
<a href="click-api/org/apache/click/control/ActionLink.html#getTitle()">ActionLink.getTitle()</a>
</li>
<li>
<a href="click-api/org/apache/click/control/Field.html#getLabel()">Field.getLabel()</a>
</li>
<li>
<a href="click-api/org/apache/click/control/Field.html#getTitle()">Field.getTitle()</a>
</li>
<li>
<a href="click-api/org/apache/click/control/FieldSet.html#getLegend()">FieldSet.getLegend()</a>
</li>
</ul>
<h4>Field Messages</h4>
The Field control classes share a common messages properties file:
<pre class="codeConfig">
/click-control.properties </pre>
The field class provides a number of
<a href="click-api/org/apache/click/control/Field.html#getMessage(java.lang.String)">getMessage(String)</a>
methods which support localized strings and message formatting.
Please also see the Control topic <a href="controls.html#message-properties">Message Properties</a>.
</dd>
<a name="utf8-encoding" class="heading"></a>
<dt><b>10.&nbsp; How do you encode Pages in the UTF-8 character set?</b></dt>
<dd>
To encode pages in the UTF-8 character set you need to create a
<tt>WEB-INF/velocity.properties</tt> file with the properties:
<pre class="codeConfig">
<span class="red">input.encoding</span>=<span class="blue">UTF-8</span> </pre>
This will configure the Velocity runtime to use UTF-8.
<p/>
You will also need to set the page headers content type to UTF-8. You can do this globally for all
your applications pages using the <tt>headers</tt> element in your
<tt>WEB-INF/click.xml</tt> file:
<pre class="codeConfig">
&lt;click&gt;
..
&lt;headers&gt;
&lt;header name="<span class="red">Content-Type</span>" value="<span class="blue">text/html;charset=UTF-8</span>"/&gt;
&lt;/headers&gt;
..
&lt;/click&gt; </pre>
This will set the pages <tt>HttpServletResponse</tt> "Content-Type" header to be
"text/html;charset=UTF-8". Alternatively you can override the Page
<a href="click-api/org/apache/click/Page.html#getContentType()">getContentType()</a> method
to this content type.
</dd>
<a name="charset" class="heading"></a>
<dt><b>11.&nbsp; How do you specify the character set which is used in your application?</b></dt>
<dd>
You can specify your application character set in <tt>WEB-INF/click.xml</tt>:
<pre class="codeConfig">
&lt;click charset="<span class="blue">UTF-8</span>"&gt;
..
&lt;/click&gt; </pre>
This character set is used for Velocity input encoding, and response Content-Type.
So if you specify the character set in <tt>WEB-INF/click.xml</tt>,
you don't have to create <tt>WEB-INF/velocity.properties</tt>.
<p/>
If you want to use the other character set in your Velocity templates,
you can override input encoding by <tt>WEB-INF/velocity.properties</tt>.
See <a href="#utf8-encoding">the previous topic</a>.
</dd>
<a name="multiple-posts" class="heading"></a>
<dt><b>12.&nbsp; How can you prevent multiple form posts?</b></dt>
<dd>
You can prevent multiple form posts by using the Post Redirect pattern. With
this pattern once the user has posted a form you redirect to another page.
If the user then presses the refresh button, they will making a GET request on the
current page.
<p/>
Please see the <a target="blank" href="http://www.theserverside.com/articles/content/RedirectAfterPost/article.html">Redirect After Post</a>
article for more information on this topic.
<p/>
To prevent users resubmitting a form with the browser back button use the
Form
<a href="click-api/org/apache/click/control/Form.html#onSubmitCheck(org.apache.click.Page, java.lang.String)">onSubmitCheck()</a>
method:
<pre class="codeJava">
<span class="kw">public class</span> Purchase <span class="kw">extends</span> Page {
..
<span class="kw">public boolean</span> onSecurityCheck() {
<span class="kw">return</span> form.onSubmitCheck(<span class="kw">this</span>, <span class="st">"/invalid-submit.html"</span>);
}
} </pre>
<p/>
Please see the Click Examples 'Page Flow' for a demonstration of the
Post-Redirect and submit check patterns.
</dd>
<a name="html-pages"></a>
<dt><b>13.&nbsp; How can I use *.html Click pages?</b></dt>
<dd>
Click does not support *.html files as Click pages. These files are not
processed by the ClickServlet and are intended for use as static content.
</dd>
<a name="alternative-extension"></a>
<dt><b>14.&nbsp; Can Click be mapped to an extension other than *.htm?</b></dt>
<dd>
Currently Click only supports *.htm extension. You cannot create templates
with a different extension for example '.xml'.
<p/>
However you can map URLs to different extensions using
<a href="http://tuckey.org/urlrewrite/">Url Rewrite Filter</a>. It is even
possible to rewrite to REST like URLs:
<ul>
<li>rewrite URL from <span style="color:red;font-style:italic">http://www.mycorp.com/book.htm?id=324</span> to <span style="color:blue;font-style:italic">http://www.mycorp.com/book/324</span> (which will retrieve the book where id=324)</li>
<li>rewrite URL from <span style="color:red;font-style:italic">http://www.mycorp.com/books.htm</span> to <span style="color:blue;font-style:italic">http://www.mycorp.com/books</span> (which will retrieve the list of books)</li>
</ul>
</dd>
<a name="cayenne-integration" class="heading"></a>
<dt><b>15.&nbsp; What JARs should I use with Click and Cayenne?</b></dt>
<dd>
To get Click and Cayenne to work happily with each other you will need to
include the following JAR files in your WEB-INF/lib directory:
<ul style="margin-top:1em;">
<li>ashwood-1.1.jar</li>
<li>cayenne-nodeps-1.2.x.jar</li>
<li>click-1.x.jar</li>
<li>click-extras-1.x.jar</li>
<li>log4j-1.2.x.jar</li>
<li>oro-2.0.8.jar</li>
</ul>
The default Cayenne JAR includes Velocity 1.3 which is not compatible with
Click which uses Velocity 1.5-dev, so instead we use the Cayenne no
dependencies JAR. When using Cayenne nodeps JAR we need to add some additional
Java libraries which include ashwood, log4j and oro.
</dd>
<a name="spring-integration" class="heading"></a>
<dt><b>16.&nbsp; How can you integrate Click into Spring?</b></dt>
<dd>
To integrate Spring with Click configure the
<a href="extras-api/org/apache/click/extras/spring/SpringClickServlet.html">SpringClickServlet</a>
instead of the normal ClickServlet. The SpringClickServlet is contained in the
<a href="extras.html">Extras</a> library.
<p/>
The Spring MVC Framework however, is not compatible with Click. The Spring framework
uses a low level command pattern design like Struts and WebWork.
Spring uses a <tt>DispatcherServlet</tt> to route requests to <tt>Controller</tt>
objects and then passes the <tt>ModelAndView</tt> results to the rendering layer.
<pre class="codeJava">
public interface Controller {
public ModelAndView handleRequest(HttpServletRequest request,
HttpServletResponse response) throws Exception;
} </pre>
In Spring MVC the integration plugin points are the Controllers.
<p/>
Click uses higher level design constructs focusing on Pages and Controls. Click uses its
own <tt>ClickServlet</tt> for dispatching requests to <tt>Pages</tt> and <tt>Control</tt>s,
which are Click's plugin points.
</dd>
<a name="jsp-support" class="heading"></a>
<dt><b>17.&nbsp; Does Click support JSP?</b></dt>
<dd>
Click fully supports JSP pages.
<p/>
JSP Pages can be automatically loaded, like Velocity templates, and
can be explicitly defined in the <tt>click.xml</tt> file.
<pre class="codeConfig">
&lt;page path="<span class="blue">customers-table.jsp</span>" class="<span class="red">com.mycorp.pages.CustomersTable</span>"/&gt; </pre>
The page's model data values are automatically added to the request as
attributes so they are available in the JSP. Other Click values added
as request attributes include:
<p/>
<ul>
<li>context &nbsp; - &nbsp;
the Servlet context path, e.g. <span class="">/mycorp</span>
</li>
<li>format &nbsp; - &nbsp;
the <a href="click-api/org/apache/click/util/Format.html">Format</a>
object for formatting the display of objects
</li>
<li>forward &nbsp; - &nbsp;
the page JSP resource (.jsp file)
</li>
<li>messages &nbsp; - &nbsp;
the <a target="topic" href="click-api/org/apache/click/util/MessagesMap.html">MessagesMap</a> adaptor
for the Page <a href="click-api/org/apache/click/Page.html#getMessage(java.lang.String)">getMessage()</a>
method
</li>
<li>path &nbsp; - &nbsp; the mapped request <a href="click-api/org/apache/click/Page.html#path">path</a>
of the page. Note this will have a .htm not a .jsp extension
</li>
</ul>
<p/>
</dd>
<a name="pdf-and-excel-rendering" class="heading"></a>
<dt><b>18.&nbsp; How can I render PDF and Excel documents?</b></dt>
<dd>
By making use of the <a href="pages.html#page-direct-rendering">Direct Rendering</a>
support you can render directly to the servlet response and bypass the page
template rendering.
<p/>
Here is an example to render either a PDF or Excel document:
<pre class="prettyprint">
public MyPage extends Page {
/** The PDF report type request parameter. */
public static final String PDF = "pdf";
/** The Excel report type request parameter. */
public static final String EXCEL = "excel";
/**
* The Page#onGet renders the report to the servlet output stream.
*/
public void onGet() {
HttpServletResponse response = getContext().getResponse();
// report type is a request parameter which specifies either PDF or Excel
String reportType = getContext().getRequestParameter("reportType");
// Retrieve either a PDF or Excel document as an InputStream
InputStream inputStream = getInputStream(reportType);
// Set response headers
String mimeType = getMimeType(reportType);
response.setHeader("Content-Disposition", "attachment; filename=\"report.pdf\"");
response.setContentType(mimeType);
response.setHeader("Pragma", "no-cache");
OutputStream outputStream = null;
try {
outputStream = response.getOutputStream();
// Write out PDF Document to response stream
IOUtils.copy(inputStream, outputStream);
// By setting the Page path to null, we bypass template rendering
setPath(null);
} catch (IOException ioe) {
throw new RuntimeException(ioe);
} finally {
ClickUtils.close(outputStream);
}
}
/**
* This method should contain the logic to retrieve the report as either a PDF
* or Excel document.
*/
public InputStream getReport(String reportType) {
InputStream intputStream = null;
if (PDF.equals(reportType)) {
...
} else if (EXCEL.equals(reportType)) {
...
}
return intputStream;
}
/**
* This method returns the report mime type based on the specified report type.
*/
public String getMimeType(String reportType) {
if (PDF.equals(reportType)) {
return ClickUtils.getMimeType(".pdf");
} else if (EXCEL.equals(reportType)) {
return ClickUtils.getMimeType(".xls");
}
}
}
</pre>
<p/>
</dd>
<a name="performance" class="heading"></a>
<dt><b>19.&nbsp; What is the performance of Click?</b></dt>
<dd>
Click is fast.
<p/>
When the Click framework processes a request it creates a relatively small
number of objects. These include a Page, a Context, a Format and a number of
Contols which in turn contain some Lists, Maps and Strings.
<p/>
The allocation of small/moderate numbers of short lived objects by
modern JVMs is very, very fast. Please see the IBM article
<a target="blank" class="external" href="http://www-128.ibm.com/developerworks/java/library/j-jtp09275.html">Urban performance legends, revisited</a>.
<p/>
The amount of actual work Click does is pretty small.
<p/>
The <tt>onProcess()</tt> methods traverse a list of Controls and do simple
operations.
<p/>
The Control <tt>toString()</tt> methods can allocate large StringBuffers when
rendering tables, but forms rarely get larger than 4,000 characters.
When Click creates a new StringBuffer it attempts to determine the
maximum likely size to avoid additional memory allocation and arraycopy
operations.
<p/>
There is not much reflection in Click at all. With reflection only really used by
the Control call back listeners:
<blockquote>
<tt style="white-space:nowrap">okButton.setListener(<span class="kw">this</span>, <span class="st">"onOkClicked"</span>);</tt>
</blockquote>
The next step in processing the request is rendering the response.
Velocity is largely responsible for this step.
<p/>
Velocity is also fast.
<p/>
While hard performance numbers are difficult to come by in this area,
until recently Velocity was considered to be faster than JSP.
However, recent discussions on Velocity mail lists indicate that JSP
compilers have improved to the point where JSP has a small performance lead over
Velocity. What ever the case, JSP is very fast and so is Velocity.
</dd>
<a name="unit-testing"></a>
<dt><b>20.&nbsp; How do I unit test Click pages?</b></dt>
<dd>
It is generally recommended that you don't write JUnit style automated unit
tests for Click pages as the cost to benefit ratio is quite poor.
If you have complex business logic in an Click page you should refactor this
code into a business level service class which you can readily unit test and
reuse in multiple places.
<p/>
If you still need to write unit tests for your Click pages, please read the
<a href="mock-api/overview-summary.html">documentation</a> on the
<a href="mock-api/org/apache/click/MockContainer.html">MockContainer</a> and
<a href="mock-api/org/apache/click/MockContext.html">MockContext</a> classes.
</dd>
<a name="logging" class="heading"></a>
<dt><b>21.&nbsp; Why doesn't Click use Commons Logging / Log4J for logging?</b></dt>
<dd>
Click by default does not use Commons Logging / Log4J to avoid the class
loader and configuration issues which often occur with these framework, and
instead default to System.out using the <tt>ConsoleLogger</tt>.
<p/>
Click provides support for configurable <tt>LogService</tt>s and provides
<tt>JdkLogService</tt> and <tt>Log4JLogService</tt> classes in Click Extras.
</dd>
<a name="why-velocity" class="heading"></a>
<dt><b>22.&nbsp; Why doesn't Click use FreeMarker instead of Velocity as the default template engine?</b></dt>
<dd>
FreeMarker is a powerful templating engine which was evaluated along side
Velocity for use in Click. While FreeMarker has many sophisticated
features Velocity lacks, Velocity was chosen as the default engine because
it is easier to learn and doesn't use an XML style markup syntax.
<p/>
Please note however that Click provides support for FreeMarker with the
<tt>FreemarkerTemplateService</tt> in Click Extras.
</dd>
<a name="why-click" class="heading"></a>
<dt><b>23.&nbsp; Why develop a new Web Application Framework?</b></dt>
<dd>
Because the existing frameworks did not meet my needs. Struts doesn't really do much,
while Tapestry is too complicated.
<p/>
For a more comprehensive answer please see <a href="why-click.html">Why Click</a>.
</dd>
</dl>
</body>
</html>