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<a name="about_this_guide"></a><div class="section"><h2>About this Guide</h2>
<p>
This guide is the reference for the Velocity Template Language
(VTL). For more information, please also refer to the <a href="user-guide.html">Velocity User Guide</a>.
</p>
</div>
<a name="references"></a><div class="section"><h2>References</h2>
<a name="variables"></a><div class="section"><h3>Variables</h3>
<p>
Notation:
</p>
<p>
<strong>$</strong> [ <strong>!</strong> ][ <strong>{</strong> ][
<strong>a..z</strong>, <strong>A..Z</strong> ][ <strong>a..z</strong>,
<strong>A..Z</strong>, <strong>0..9</strong>, <strong>-</strong>,
<strong>_</strong> ][ <strong>}</strong> ]
</p>
<p>
Examples:
</p>
<ul>
<li>Normal notation: <variable>$mud-Slinger_9</variable></li>
<li>Silent notation: <variable>$!mud-Slinger_9</variable></li>
<li>Formal notation: <variable>${mud-Slinger_9}</variable></li>
</ul>
</div>
<a name="properties"></a><div class="section"><h3>Properties</h3>
<p>
Notation:
</p>
<p>
<strong>$</strong> [ <strong>{</strong> ][ <strong>a..z</strong>,
<strong>A..Z</strong> ][ <strong>a..z</strong>, <strong>A..Z</strong>,
<strong>0..9</strong>, <strong>-</strong>, <strong>_</strong> ]*
<strong>.</strong>[<strong>a..z</strong>, <strong>A..Z</strong> ][
<strong>a..z</strong>, <strong>A-Z</strong>, <strong>0..9</strong>,
<strong>-</strong>, <strong>_</strong> ]* [ <strong>}</strong> ]
</p>
<p>
Examples:
</p>
<ul>
<li>Regular Notation: $customer.Address</li>
<li>Formal Notation: ${purchase.Total}</li>
</ul>
</div>
<a name="methods"></a><div class="section"><h3>Methods</h3>
<p>
Notation:
</p>
<p>
<strong>$</strong> [ <strong>{</strong> ][ <strong>a..z</strong>,
<strong>A..Z</strong> ][ <strong>a..z</strong>, <strong>A..Z</strong>,
<strong>0..9</strong>, <strong>-</strong>, <strong>_</strong> ]*
<strong>.</strong>[ <strong>a..z</strong>, <strong>A..Z</strong> ][
<strong>a..z</strong>, <strong>A..Z</strong>, <strong>0..9</strong>,
<strong>-</strong>, <strong>_</strong> ]*<strong>(</strong> [
<i>optional parameter list...</i> ] <strong>)</strong> [
<strong> } </strong>]
</p>
<p>
Examples:
</p>
<ul>
<li>Regular Notation: $customer.getAddress()</li>
<li>Formal Notation: ${purchase.getTotal()}</li>
<li>Regular Notation with Parameter List: $page.setTitle( &quot;My Home
Page&quot; )</li>
</ul>
</div>
<p>
VTL Properties can be used as a shorthand notation for VTL Methods
that take <em>get</em> and <em>set</em>. Either
<em>$object.getMethod()</em> or <em>$object.setMethod()</em> can be
abbreviated as <em>$object.Method</em>. It is generally preferable to
use a Property when available. The main difference between Properties
and Methods is that you can specify a parameter list to a Method.
</p>
</div>
<a name="directives"></a><div class="section"><h2>Directives</h2>
<a name="aset_-_establishes_the_value_of_a_reference"></a><div class="section"><h3>#set - Establishes the value of a reference</h3>
<p>
Format:
</p>
<p>
<strong>#</strong> [ <strong>{</strong> ] <strong>set</strong> [ <strong>}</strong> ] <strong> ( $</strong>ref <strong>=</strong> [ <strong>&quot;</strong>,
<strong>'</strong> ]arg[ <strong>&quot;</strong>, <strong>'</strong> ] )
</p>
<p>
Usage:
</p>
<ul>
<li><em>$ref</em> - The LHS of the assignment must be a variable
reference or a property reference.</li>
<li><em>arg</em> - The RHS of the assignment, <em>arg</em> is parsed
if enclosed in double quotes, and not parsed if enclosed in single
quotes. If the RHS evaluates to <em>null</em>, it is <b>not</b>
assigned to the LHS.</li>
</ul>
<p>
Examples:
</p>
<ul>
<li>Variable reference: #set( $monkey = $bill )</li>
<li>String literal: #set( $monkey.Friend = 'monica' )</li>
<li>Property reference: #set( $monkey.Blame = $whitehouse.Leak
)</li>
<li>Method reference: #set( $monkey.Plan = $spindoctor.weave($web)
)</li>
<li>Number literal: #set( $monkey.Number = 123 )</li>
<li>Range operator: #set( $monkey.Numbers = [1..3] )</li>
<li>Object array: #set( $monkey.Say = [&quot;Not&quot;, $my, &quot;fault&quot;] )</li>
</ul>
<p>
The RHS can also be a simple arithmetic expression, such as:
</p>
<ul>
<li>Addition: #set( $value = $foo + 1 )</li>
<li>Subtraction: #set( $value = $bar - 1 )</li>
<li>Multiplication: #set( $value = $foo * $bar )</li>
<li>Division: #set( $value = $foo / $bar )</li>
<li>Remainder: #set( $value = $foo % $bar )</li>
</ul>
</div>
<a name="aifelseifelse-outputconditionalontruthofstatements"></a><div class="section"><h3>#if/#elseif/#else-outputconditionalontruthofstatements</h3>
<p>
Format:
</p>
<p>
<strong>#</strong> [ <strong>{</strong> ] <strong>if</strong> [ <strong>}</strong> ] <strong>(</strong> [condition] <strong>)</strong> [output] [
<strong>#</strong> [ <strong>{</strong> ] <strong>elseif</strong> [ <strong>}</strong> ] <strong>( </strong>[condition] <strong>)</strong> [output] ]* [
<strong>#</strong> [ <strong>{</strong> ] <strong>else</strong> [ <strong>}</strong> ] [output] ]
<strong>#</strong> [ <strong>{</strong> ] <strong>end</strong> [ <strong>}</strong> ]
</p>
<p>
Usage:
</p>
<ul>
<li><em>condition</em> - If a boolean, considered true if it has a
true false; if not a boolean, considered true if not null.</li>
<li><em>output</em> - May contain VTL.</li>
</ul>
<p>
Examples (showing different operators):
</p>
<table class="bodyTable">
<tr class="a">
<th >Operator Name</th>
<th >Symbol</th>
<th >Alternative Symbol</th>
<th >Example</th>
</tr>
<tr class="b">
<td >Equals Number</td>
<td >==</td>
<td >eq</td>
<td > #if( $foo == 42 )</td>
</tr>
<tr class="a">
<td >Equals String</td>
<td >==</td>
<td >eq</td>
<td > #if( $foo == &quot;bar&quot; )</td>
</tr>
<tr class="b">
<td >Object Equivalence</td>
<td >==</td>
<td >eq</td>
<td > #if( $foo == $bar )</td>
</tr>
<tr class="a">
<td >Not Equals</td>
<td >!=</td>
<td >ne</td>
<td > #if( $foo != $bar )</td>
</tr>
<tr class="b">
<td >Greater Than</td>
<td >&gt;</td>
<td >gt</td>
<td > #if( $foo &gt; 42 )</td>
</tr>
<tr class="a">
<td >Less Than</td>
<td >&lt;</td>
<td >lt</td>
<td > #if( $foo &lt; 42 )</td>
</tr>
<tr class="b">
<td >Greater Than or Equal To</td>
<td >&gt;=</td>
<td >ge</td>
<td > #if( $foo &gt;= 42 )</td>
</tr>
<tr class="a">
<td >Less Than or Equal To</td>
<td >&lt;=</td>
<td >le</td>
<td > #if( $foo &lt;= 42 )</td>
</tr>
<tr class="b">
<td >Boolean NOT</td>
<td >!</td>
<td >not</td>
<td > #if( !$foo )</td>
</tr>
</table>
<p>Notes:</p>
<ol type="1">
<li>
The == operator can be used to compare numbers, strings, objects of the same class, or objects
of different classes. In the last case (when objects are of different classes), the toString()
method is called on each object and the resulting Strings are compared.
</li>
<li>
You can also use brackets to delimit directives. This is especially
useful when text immediately follows an <code>#else</code> directive.
</li>
</ol>
<div class="source"><pre>
#if( $foo == $bar)it's true!#{else}it's not!#end&lt;/li&gt;
</pre></div>
</div>
<a name="aforeach_-_loops_through_a_list_of_objects"></a><div class="section"><h3>#foreach - Loops through a list of objects</h3>
<p>
Format:
</p>
<p>
<strong>#</strong> [ <strong>{</strong> ] <strong>foreach</strong> [ <strong>}</strong> ] <strong>(</strong> <em>$ref</em> <strong>in</strong> <em>arg</em>
<strong>)</strong> <em>statement</em>
<strong>#</strong> [ <strong>{</strong> ] <strong>end</strong> [ <strong>}</strong> ]
</p>
<p>
Usage:
</p>
<ul>
<li><em>$ref</em> - The first variable reference is the item.</li>
<li><em>arg</em> - May be one of the following: a reference to a
list (i.e. object array, collection, or map), an array list, or
the range operator.</li>
<li>
<em>statement</em> - What is output each time Velocity finds a
valid item in the list denoted above as <i>arg</i>. This output is
any valid VTL and is rendered each iteration of the loop.
</li>
</ul>
<p>
Examples of the #foreach(), omitting the statement block :
</p>
<ul>
<li>Reference: #foreach ( $item in $items )</li>
<li>Array list: #foreach ( $item in [&quot;Not&quot;, $my, &quot;fault&quot;] )</li>
<li>Range operator: #foreach ( $item in [1..3] )</li>
</ul>
<p>
Velocity provides an easy way to get the loop counter so that you
can do something like the following:
</p>
<div class="source"><pre>
&lt;table&gt;
#foreach( $customer in $customerList )
&lt;tr&gt;&lt;td&gt;$velocityCount&lt;/td&gt;&lt;td&gt;$customer.Name&lt;/td&gt;&lt;/tr&gt;
#end
&lt;/table&gt;
</pre></div>
<p>
The default name for the loop counter variable reference, which is
specified in the velocity.properties file, is $velocityCount. By
default the counter starts at 1, but this can be set to either 0 or
1 in the <code>velocity.properties</code> file. Here's what the loop
counter properties section of the <code>velocity.properties</code>
file appears:
</p>
<div class="source"><pre>
# Default name of the loop counter
# variable reference.
directive.foreach.counter.name = velocityCount
# Default starting value of the loop
# counter variable reference.
directive.foreach.counter.initial.value = 1
</pre></div>
<p>
Additionally, the maximum allowed number of loop iterations can be
controlled engine-wide (an ability introduced in Velocity 1.5).
By default, there is no limit:
</p>
<div class="source"><pre>
# The maximum allowed number of loops.
directive.foreach.maxloops = -1
</pre></div>
</div>
<a name="ainclude_-_renders_local_files_that_are_not_parsed_by_velocity"></a><div class="section"><h3>#include - Renders local file(s) that are not parsed by Velocity</h3>
<p>
Format:
</p>
<p>
<strong>#</strong> [ <strong>{</strong> ] <strong>include</strong> [ <strong>}</strong> ] <strong>( </strong>arg[ arg2 ... argn]<strong> )</strong>
</p>
<ul>
<li><em>arg</em> - Refers to a valid file under TEMPLATE_ROOT.</li>
</ul>
<p>
Examples:
</p>
<ul>
<li>String: #include( &quot;disclaimer.txt&quot; &quot;opinion.txt&quot; )</li>
<li>Variable: #include( $foo $bar )</li>
</ul>
</div>
<a name="aparse_-_renders_a_local_template_that_is_parsed_by_velocity"></a><div class="section"><h3>#parse - Renders a local template that is parsed by Velocity</h3>
<p>
Format:
</p>
<p>
<strong>#</strong> [ <strong>{</strong> ] <strong>parse</strong> [ <strong>}</strong> ] <strong>(</strong> arg <strong>)</strong>
</p>
<ul>
<li><em>arg</em> - Refers to a template under TEMPLATE_ROOT.</li>
</ul>
<p>
Examples:
</p>
<ul>
<li>String: #parse( &quot;lecorbusier.vm&quot; )</li>
<li>Variable: #parse( $foo )</li>
</ul>
<p>
Recursion permitted. See <em>parse_directive.maxdepth</em> in
<code>velocity.properties</code>
to change from parse depth. (The default parse depth is 10.)
</p>
</div>
<a name="astop_-_stops_the_template_engine"></a><div class="section"><h3>#stop - Stops the template engine</h3>
<p>
Format:
</p>
<p>
<strong>#</strong> [ <strong>{</strong> ] <strong>stop</strong> [ <strong>}</strong> ]
</p>
<p>
Usage:
</p>
<p>
This will stop execution of the current template. This is good for
debugging a template.
</p>
</div>
<a name="amacro_-_allows_users_to_define_a_velocimacro_vm_a_repeated_segment_of_a_vtl_template_as_required"></a><div class="section"><h3>#macro - Allows users to define a Velocimacro (VM), a repeated segment of a VTL template, as required</h3>
<p>
Format:
</p>
<p>
<strong>#</strong> [ <strong>{</strong> ] <strong>macro</strong> [ <strong>}</strong> ] <strong>(</strong> vmname $arg1 [ $arg2 $arg3 ... $argn ]
<strong>)</strong> [ VM VTL code... ] <strong>#</strong> [ <strong>{</strong> ] <strong>#end</strong> [ <strong>}</strong> ]
</p>
<ul>
<li><em>vmname</em> - Name used to call the VM
(<em>#vmname</em>)</li>
<li><em>$arg1 $arg2 [ ... ]</em> - Arguments to the VM. There can be
any number of arguments, but the number used at invocation must
match the number specified in the definition.</li>
<li><em>[ VM VTL code... ]</em> - Any valid VTL code, anything you
can put into a template, can be put into a VM.</li>
</ul>
<p>
Once defined, the VM is used like any other VTL directive in a
template.
</p>
<div class="source"><pre>
#vmname( $arg1 $arg2 )
</pre></div>
<p>
VMs can be defined in one of two places:
</p>
<ol type="1">
<li><i>Template library:</i> can be either VMs pre-packaged with
Velocity or custom-made, user-defined, site-specific VMs;
available from any template</li>
<li><i>Inline:</i> found in regular templates, only usable when
<em>velocimacro.permissions.allowInline=true</em> in
<code>velocity.properties</code>.</li>
</ol>
</div>
</div>
<a name="comments"></a><div class="section"><h2>Comments</h2>
<p>
Comments are not rendered at runtime.
</p>
<a name="single_line"></a><div class="section"><h3>Single Line</h3>
<p>
Example:
</p>
<p>
<strong>## This is a comment.</strong>
</p>
</div>
<a name="multi_line"></a><div class="section"><h3>Multi Line</h3>
<p>
Example:
</p>
<p>
<strong>
#*<br></br>
This is a multiline comment.<br></br>
This is the second line<br></br>
*#
</strong>
</p>
</div>
</div>
</div>
</div>
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<div id="footer">
<div class="xright">&#169;
2000-2007
The Apache Software Foundation
Last Published: 2007-01-28 17:40:21
</div>
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