Velocity Template Language 101

Velocity Template Language 101

Source

Creating variables

#set( $a = "Velocity" )

The following rule of thumb may be useful to better understand how Velocity works: References begin with $ and are used to get something. Directives begin with # and are used to do something.

Comments

## This is a single line comment.

#*
  This is
  a multi-line comment
*#

References

There are three types of references in the VTL: variables, properties and methods.

Variables start with $ - e.g. $foo Properties: $customer.Address Methods: $page.setTitle( "My Home Page" )

Index notation

Using the notation of the form $foo[0] can be used to access a given index of an object

Directives

#set

The #set directive is used for setting the value of a reference. A value can be assigned to either a variable reference or a property reference, and this occurs in brackets, as demonstrated:

#set( $primate = "monkey" )
#set( $customer.Behavior = $primate )

If a right hand side is a property or method reference that evaluates to null it will not be assigned to left hand side:

#set( $result = $query.criteria("name") )
The result of the first query is $result
#set( $result = $query.criteria("address") )
The result of the second query is $result

Conditionals

#if( $foo )
  <strong>Velocity!</strong>
#end

#if( $foo < 10 )
    **Go North**
#elseif( $foo == 10 )
    **Go East**
#elseif( $bar == 6 )
    **Go South**
#else
    **Go West**
#end

Loops

#foreach loop:

<ul>
#foreach( $product in $allProducts )
    <li>$product</li>
#end
</ul>

The contents of the $allProducts variable is a Vector, a Hashtable or an Array. The value assigned to the $product variable is a Java Object and can be reference

Range operator

Example:

#foreach( $foo in [1..5] )
$foo
#end

Output:

First example:
1 2 3 4 5