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<document>

 <properties>
  <title>VTL Reference Guide</title>
  <author email="jvanzyl@zenplex.com">Velocity Documentation Team</author>
  <author email="jcastura@apache.org">John Castura</author>
 </properties>

<body>

<section name="About this Guide">
<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>

</section>

<section name="References">
    <subsection name="Variables">
    <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>
  </subsection>

  <subsection name="Properties">
    <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>
  </subsection>

  <subsection name="Methods">
    <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>opional 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( "My Home
      Page" )</li>
    </ul>
  </subsection>

  <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>

</section>

<section name="Directives">
  <subsection name="#set - Establishes the value of a reference">
    <p>
    Format:
    </p>

    <p>
    <strong>#set( $</strong>ref <strong>=</strong> [ <strong>"</strong>,
    <strong>'</strong> ]arg[ <strong>"</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 = ["Not", $my, "fault"] )</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>
  </subsection>

  <subsection name="#if / #elseif / #else - output conditional on truth
  of statements">
    <p>
    Format:
    </p>

    <p>
    <strong>#if(</strong> [condition] <strong>)</strong> [output] [
    <strong>#elseif( </strong>[condition] <strong>)</strong> [output] ]* [
    <strong>#else</strong> [output] ]
    <strong>#end</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:
    </p>

    <ul>
       <li>Equivalent Operator: #if( $foo == $bar )</li>
       <li>Greater Than: #if( $foo > 42 )</li>
       <li>Less Than: #if( $foo &lt; 42 )</li>
       <li>Greater Than or Equal To: #if( $foo >= 42 )</li>
       <li>Less Than or Equal To: #if( $foo &lt;= 42 )</li>
       <li>Equals Number: #if( $foo == 42 )</li>
       <li>Equals String: #if( $foo == "bar" )</li>
       <li>Boolean NOT: #if( !$foo )</li>
    </ul>
  </subsection>

  <subsection name="#foreach - Loops through a list of objects">
    <p>
    Format:
    </p>

    <p>
    <strong>#foreach(</strong> <em>$ref</em> <strong>in</strong> <em>arg</em>
    <strong>)</strong> <em>statement</em> <strong>#end</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 ["Not", $my, "fault"] )</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>

<source><![CDATA[
<table>
#foreach( $customer in $customerList )
    <tr><td>$velocityCount</td><td>$customer.Name</td></tr>
#end
</table>
]]></source>

    <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>

<source><![CDATA[
# Default name of the loop counter
# variable refernce.
counter.name = velocityCount

# Default starting value of the loop
# counter variable reference.
counter.initial.value = 1
]]></source>

  </subsection>

  <subsection name="#include - Renders local file(s) that are not
                    parsed by Velocity">
    <p>
    Format:
    </p>

    <p>
    <strong>#include( </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( "disclaimer.txt", "opinion.txt" )</li>
      <li>Variable: #include( $foo, $bar )</li>
    </ul>
  </subsection>

  <subsection name="#parse - Renders a local template that is parsed by
                    Velocity">
    <p>
    Format:
    </p>

    <p>
    <strong>#parse(</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( "lecorbusier.vm" )</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>
  </subsection>

  <subsection name="#stop - Stops the template engine">
    <p>
    Format:
    </p>

    <p>
    <strong>#stop</strong>
    </p>

    <p>
    Usage:
    </p>

    <p>
    This will stop execution of the current template. This is good for
    debugging a template.
    </p>
  </subsection>

  <subsection name="#macro - Allows users to define a Velocimacro (VM),
        a repeated segment of a VTL template, as required">
    <p>
    Format:
    </p>

    <p>
    <strong>#macro(</strong> vmname $arg1 [ $arg2 $arg3 ... $argn ]
    <strong>)</strong> [ VM VTL code... ] <strong>#end</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>

<source><![CDATA[
#vmname( $arg1 $arg2 )
]]></source>

    <p>
    VMs can be defined in one of two places:
    </p>

    <ol>
    <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>
  </subsection>


</section>

<section name="Comments">
    <p>
    Comments are not rendered at runtime.
    </p>

    <subsection name="Single Line">
    <p>
    Example:
    </p>

    <p>
    <strong>## This is a comment.</strong>
    </p>

    </subsection>
    <subsection name="Multi Line">
    <p>
    Example:
    </p>

    <p>
    <strong>
    #*<br/>
    This is a multiline comment.<br/>
    This is the second line<br/>
    *#
    </strong>
    </p>

    </subsection>
</section>

</body>
</document>


