一：数字型
<#assign answer=42/>
${answer}
${answer?string}  <#-- the same as ${answer} -->
${answer?string.number}
${answer?string.currency}
${answer?string.percent}

<#setting number_format="0.###E0"/>

${12345?string("0.####E0")}  


${answer?string("number")} 等同于：${answer?string.number}.

二：日期型：
预定义格式包括：short ，middle和long。

${openingTime?string.short}
${openingTime?string.medium}
${openingTime?string.long}

组合使用：${lastUpdated?string.short_long}
${lastUpdated?string("yyyy-MM-dd HH:mm:ss zzzz")}

三：逻辑型
foo?string
foo?string("yes", "no")

四：序列的内置方法：
first

last

seq_contains
${x?seq_contains("blue")?string("yes", "no")}

seq_index_of

seq_last_index_of

reverse

size

sort

sort_by
多层次的hash排序

<#assign members = [
    {"name": {"first": "Joe", "last": "Smith"}, "age": 40},
    {"name": {"first": "Fred", "last": "Crooger"}, "age": 35},
    {"name": {"first": "Amanda", "last": "Fox"}, "age": 25}]>
Sorted by name.last:
<#list members?sort_by(['name', 'last']) as m>
- ${m.name.last}, ${m.name.first}: ${m.age} years old
</#list> 

chunk：将一个序列分解成几个序列。

<#assign seq = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j']>

<#list seq?chunk(4) as row>
  <#list row as cell>${cell} </#list>
</#list>

<#list seq?chunk(4, '-') as row>
  <#list row as cell>${cell} </#list>
</#list>
chunk经常用于分栏或者表格输出的格式。

五：hash内置方法：

keys：
values：

六：很少使用或者专家级的内置方法：
byte,double,float,int,long,short。

eval

has_content：变量存在，不是指null也不是空串，一般情况下可以使用expr!?size > 0 or expr!?length > 0 代替expr?has_content。

interpret将一个字符串解析为ftl模版，产生一个TemplateTransformModel对象。
<#assign x=["a", "b", "c"]>
<#assign templateSource = "<#list x as y>${y}</#list>">
<#assign inlineTemplate = templateSource?interpret>
<@inlineTemplate>def/@inlineTemplate

is_...检查变量类型：

Built-in	Returns true if the value is a ...
is_string	string
is_number	number
is_boolean	boolean
is_date	date (all types: date-only, time-only and date-time)
is_method	method
is_transform	transform
is_macro	macro
is_hash	hash
is_hash_ex	extended hash (i.e. supports ?keys and ?values)
is_sequence	sequence
is_collection	collection
is_enumerable	sequence or collection
is_indexable	sequence
is_directive	macro or transform
is_node	node

namespace：返回宏变量的命名空间，只能用于宏。

new：创建一个TemplateModel实现的变量。
<#assign word_wrapp = "com.acmee.freemarker.WordWrapperTransform"?new()>