Velocity - VTL Reference Guide

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About this Guide
This guide is the reference for the Velocity Template Language (VTL). For more information, please also refer to the Velocity User Guide.
References
> Variables
> Notation: $ [ ! ][ { ][ a..z, A..Z ][ a..z, A..Z, 0..9, -, _ ][ } ] Examples: Normal notation: $mud-Slinger_9 Silent notation: $!mud-Slinger_9 Formal notation: ${mud-Slinger_9}
> Properties
> Notation: $ [ { ][ a..z, A..Z ][ a..z, A..Z, 0..9, -, _ ]* .[a..z, A..Z ][ a..z, A-Z, 0..9, -, _ ]* [ } ] Examples: Regular Notation: $customer.Address Formal Notation: ${purchase.Total}
> Methods
> Notation: $ [ { ][ a..z, A..Z ][ a..z, A..Z, 0..9, -, _ ]* .[ a..z, A..Z ][ a..z, A..Z, 0..9, -, _ ]*( [ opional parameter list... ] ) [ } ] Examples: Regular Notation: $customer.getAddress() Formal Notation: ${purchase.getTotal()} Regular Notation with Parameter List: $page.setTitle( "My Home Page" )
VTL Properties can be used as a shorthand notation for VTL Methods that take get and set. Either $object.getMethod() or $object.setMethod() can be abbreviated as $object.Method. 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.
Directives
> #set - Establishes the value of a reference
> Format: #set( $ref = [ ", ' ]arg[ ", ' ] ) Usage: $ref - The LHS of the assignment must be a variable reference or a property reference. arg - The RHS of the assignment, arg is parsed if enclosed in double quotes, and not parsed if enclosed in single quotes. If the RHS evaluates to null, it is not assigned to the LHS. Examples: Variable reference: #set( $monkey = "bill" ) String literal: #set( $monkey.Friend = "monica" ) Property reference: #set( $monkey.Blame = $whitehouse.Leak ) Method reference: #set( $monkey.Plan = $spindoctor.weave($web) ) Number literal: #set( $monkey.Number = 123 ) Range operator: #set( $monkey.Numbers = [1..3] ) Object array: #set( $monkey.Say = ["Not", $my, "fault"] ) The RHS can also be a simple arithmetic expression, such as: Addition: #set( $value = $foo + 1 ) Subtraction: #set( $value = $bar - 1 ) Multiplication: #set( $value = $foo * $bar ) Division: #set( $value = $foo / $bar ) Remainder: #set( $value = $foo % $bar )
> #if / #elseif / #else - output conditional on truth of statements
> Format: #if( [condition] ) [output] [ #elseif( [condition] ) [output] ]* [ #else [output] ] #end Usage: condition - If a boolean, considered true if it has a true false; if not a boolean, considered true if not null. output - May contain VTL. Examples: Equivalent Operator: #if( $foo == $bar ) Greater Than: #if( $foo > 42 ) Less Than: #if( $foo < 42 ) Greater Than or Equal To: #if( $foo >= 42 ) Less Than or Equal To: #if( $foo <= 42 ) Equals Number: #if( $foo == 42 ) Equals String: #if( $foo == "bar" ) Boolean NOT: #if( !$foo )
> #foreach - Loops through a list of objects
> > Format: #foreach( $ref in arg ) statement #end Usage: $ref - The first variable reference is the item. arg - 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. statement - What is output each time Velocity finds a valid item in the list denoted above as arg. This output is any valid VTL and is rendered each iteration of the loop. Examples of the #foreach(), omitting the statement block : Reference: #foreach ( $item in $items ) Array list: #foreach ( $item in ["Not", $my, "fault"] ) Range operator: #foreach ( $item in [1..3] ) Velocity provides an easy way to get the loop counter so that you can do something like the following:
> >     <table>
> >     #foreach( $customer in $customerList )
> >         <tr><td>$velocityCount</td><td>$customer.Name</td></tr>
> >     #end
> >     </table>
> > 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 `velocity.properties` file. Here's what the loop counter properties section of the `velocity.properties` file appears:
> >     # Default name of the loop counter
> >     # variable refernce.
> >     counter.name = velocityCount

> >     # Default starting value of the loop
> >     # counter variable reference.
> >     counter.initial.value = 1
> #include - Renders local file(s) that are not parsed by Velocity
> Format: #include( arg[, arg2, ... argn] ) arg - Refers to a valid file under TEMPLATE_ROOT. Examples: String: #include( "disclaimer.txt", "opinion.txt" ) Variable: #include( $foo, $bar )
> #parse - Renders a local template that is parsed by Velocity
> Format: #parse( arg ) arg - Refers to a template under TEMPLATE_ROOT. Examples: String: #parse( "lecorbusier.vm" ) Variable: #parse( $foo ) Recursion permitted. See parse_directive.maxdepth in `velocity.properties` to change from parse depth. (The default parse depth is 10.)
> #stop - Stops the template engine
> Format: #stop Usage: This will stop execution of the current template. This is good for debugging a template.
> #macro - Allows users to define a Velocimacro (VM), a repeated segment of a VTL template, as required
> > Format: #macro( vmname $arg1 [ $arg2 $arg3 ... $argn ] ) [ VM VTL code... ] #end vmname - Name used to call the VM (#vmname) $arg1 $arg2 [ ... ] - 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. [ VM VTL code... ] - Any valid VTL code, anything you can put into a template, can be put into a VM. Once defined, the VM is used like any other VTL directive in a template.
> >     #vmname( $arg1 $arg2 )
> VMs can be defined in one of two places: Template library: can be either VMs pre-packaged with Velocity or custom-made, user-defined, site-specific VMs; available from any template Inline: found in regular templates, only usable when velocimacro.permissions.allowInline=true in `velocity.properties`.
Comments
> Comments are not rendered at runtime.
> Single Line
> Example: ## This is a comment.
> Multi Line
> Example: #* This is a multiline comment. This is the second line *#
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