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import java.io.StringWriter;
import org.apache.velocity.app.VelocityEngine;
import org.apache.velocity.Template;
import org.apache.velocity.VelocityContext;
public class HelloWorld
{
public static void main( String[] args )
throws Exception
{
/* first, get and initialize an engine */
VelocityEngine ve = new VelocityEngine();
ve.init();
/* next, get the Template */
Template t = ve.getTemplate( "helloworld.vm" );
/* create a context and add data */
VelocityContext context = new VelocityContext();
context.put("name", "World");
/* now render the template into a StringWriter */
StringWriter writer = new StringWriter();
t.merge( context, writer );
/* show the World */
System.out.println( writer.toString() );
}
}
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Hello World! Welcome to Velocity! |
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$petList.size() Pets on Sale!
We are proud to offer these fine pets
at these amazing prices. This month only,
choose from:
#foreach( $pet in $petList )
$pet.name for only $pet.price
#end
Call Today!
|
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/* create our list of maps */
ArrayList list = new ArrayList();
Map map = new HashMap();
map.put("name", "horse");
map.put("price", "00.00");
list.add( map );
map = new HashMap();
map.put("name", "dog");
map.put("price", "9.99");
list.add( map );
map = new HashMap();
map.put("name", "bear");
map.put("price", ".99");
list.add( map );
/* add that list to a VelocityContext */
VelocityContext context = new VelocityContext();
context.put("petList", list);
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import java.io.StringWriter;
import java.util.List;
import java.util.ArrayList;
import java.util.Map;
import java.util.HashMap;
import org.apache.velocity.Template;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.VelocityEngine;
public class PetStoreEmail
{
public static void main( String[] args )
throws Exception
{
/* first, get and initialize an engine */
VelocityEngine ve = new VelocityEngine();
ve.init();
/* organize our data */
ArrayList list = new ArrayList();
Map map = new HashMap();
map.put("name", "horse");
map.put("price", "00.00");
list.add( map );
map = new HashMap();
map.put("name", "dog");
map.put("price", "9.99");
list.add( map );
map = new HashMap();
map.put("name", "bear");
map.put("price", ".99");
list.add( map );
/* add that list to a VelocityContext */
VelocityContext context = new VelocityContext();
context.put("petList", list);
/* get the Template */
Template t = ve.getTemplate( "petstoreemail.vm" );
/* now render the template into a Writer */
StringWriter writer = new StringWriter();
t.merge( context, writer );
/* use the output in your email body */
sendEmail( writer.toString() );
}
}
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3 Pets on Sale!
We are proud to offer these fine pets
at these amazing prices. This month only,
choose from:
horse for only 00.00
dog for only 9.99
bear for only .99
Call Today!
|
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#set()
#if()
#else
#elseif()
#end
#foreach()
#include()
#parse()
#macro()
|
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#set( $startrow = 0)
#set( $count = $current + 1 )
#set( $isReady = ( $isOn && $isOpen) )
#if( $value > 5 )
bigger
#elseif( $value < 5 )
smaller
#else
just right
#end
#foreach( $item in $itemList )
My $item.
#end
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The collection types #foreach() supports are:
Object[]
java.util.Collection
java.util.Map (iterates over the mapped values)
java.util.Iterator
java.util.Enumeration
The #include() and #parse() directives are similar -- they both take a template or static resource name as an argument, include that template or resource in-place, and then render it to the output stream. The difference is that #include() includes the specified resource's content without any processing, and #parse() treats the specified resource as a template, processing all directives and references against the current context.
You can use these two directives to dynamically construct output. For example, in Web applications you can set up a skeleton for your pages, such as a set of top-level templates that may employ different navigational layouts or color/design schemes, and then #parse() and/or #include() the dynamic and static content elements at runtime based on user and application state:
| #parse( $header ) |
| #parse( $body ) |
| #parse( $footer ) |
提示：velocity中大小写敏感。
Velocity还特别提供了得到循环次数的方法，$velocityCount变量的名字是Velocity默认的名字。
Velocity中的宏我们可以理解为函数。
①宏的定义
#macro(宏的名称 $参数1 $参数2 …)
语句体(即函数体)
#end
②宏的调用
#宏的名称($参数1 $参数2 …)
说明：参数之间用空格隔开。
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#macro( select $name $displayname $choicelist )
<SELECT name=$name>
<option value="">$displayname</option>
#foreach( $choice in $choicelist )
<option value=$choice>$choice</option>
#end
</select>
#end
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Then, anytime you need an HTML <select> widget, you could simply invoke the Velocimacro as a directive:
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Please choose: #select( "size" "--SIZE--" $sizelist ) |
VTL miscellany
I should mention a few other VTL features. VTL lets you create integers, string literals, Boolean values, arrays of objects, and arrays of sequential integers in the template:
#set( $myint = 5 )
#set( $mystring = 'Hello There')
#set( $mybool = true )
#set( $objarr = [ "a", $myint, $mystring, false ] )
#set( $intrangearr = [1..10] )
VTL also has an alternative string literal form, using double quotes (") that interpolates reference values (plus directives and Velocimacros):
#set( $foo = 'bar')
#set( $interp = "The value is '$foo'")
The resulting value of $interp is the string The value is 'bar'.
/n/n/n/n/n
#include和#parse的作用都是引入本地文件, 为了安全的原因，被引入的本地文件只能在TEMPLATE_ROOT目录下。
区别：
(1) 与#include不同的是，#parse只能指定单个对象。而#include可以有多个
如果您需要引入多个文件，可以用逗号分隔就行：
#include ("one.gif", "two.txt", "three.htm" )
在括号内可以是文件名，但是更多的时候是使用变量的：
#include ( “greetings.txt”, $seasonalstock )
(2) #include被引入文件的内容将不会通过模板引擎解析；
而#parse引入的文件内容Velocity将解析其中的velocity语法并移交给模板，意思就是说相当与把引入的文件copy到文件中。
#parse是可以递归调用的，例如：如果dofoo.vm包含如下行：
Count down.
#set ($count = 8)
#parse ("parsefoo.vm")
All done with dofoo.vm!
那么在parsefoo.vm模板中，你可以包含如下VTL：
$count
#set($count = $count - 1)
#if ( $count > 0 )
#parse( "parsefoo.vm" )
#else
All done with parsefoo.vm!
#end的显示结果为：
Count down.
8
7
6
5
4
3
2
1
0
All done with parsefoo.vm!
All done with dofoo.vm!
注意：在vm中使用#parse来嵌套另外一个vm时的变量共享问题。如：
->a.vm 里嵌套 b.vm；
->a.vm 里定义了变量 $param；
->b.vm 里可以直接使用$param，无任何限制。
但需要特别注意的是，如果b.vm里同时定义有变量$param，则b.vm里将使用b.vm里定义的值