Java模板引擎之FreeMarker

FreeMarker 是一个采用 Java 开发的模版引擎，是一个基于模版生成文本的通用工具。 它被设计用来生成 HTML Web 页面，特别是基于 MVC 模式的应用程序。虽然使用FreeMarker需要具有一些编程的能力，但通常由 Java 程序准备要显示的数据，由 FreeMarker 生成页面，并通过模板显示准备的数据。

http://freemarker.org/

版本：2.3.19

public void process(String template, Map<String, ?> data) throws Exception {
	Configuration cfg = new Configuration();
	cfg.setDirectoryForTemplateLoading(new File("ftl"));
	cfg.setObjectWrapper(new DefaultObjectWrapper());
	
	//设置字符集
	cfg.setDefaultEncoding("UTF-8");
	
	//设置尖括号语法和方括号语法,默认是自动检测语法
	//  自动 AUTO_DETECT_TAG_SYNTAX
	//  尖括号 ANGLE_BRACKET_TAG_SYNTAX
	//  方括号 SQUARE_BRACKET_TAG_SYNTAX
	cfg.setTagSyntax(Configuration.AUTO_DETECT_TAG_SYNTAX);

	Writer out = new OutputStreamWriter(new FileOutputStream(FILE_DIR + template + ".txt"),"UTF-8");
	Template temp = cfg.getTemplate(template);
	temp.process(data, out);
	out.flush();
}

1、计算式

引用

<#-- 1、算术运算 -->[BR]
${3 + 4}

<#-- 2、内建函数 -->[BR]
${"rensanning"?upper_case}

2、输出一个值

HashMap t2root = new HashMap<String, String>();
t2root.put("user", "RenSanNing");

引用

${user}, Welcome!

3、输出一个列表

Map<String, Object> t3root = new HashMap<String, Object>();
List<Food> menu = new ArrayList<Food>();
menu.add(new Food("iText in Action", 98));
menu.add(new Food("iBATIS in Action", 118));
menu.add(new Food("Lucene in Action", 69));
t3root.put("menu", menu);

引用

<#list menu as food>
${food.name}  ${food.price?string.currency}
</#list>

4、逻辑判断（IF,SWITCH)

Map<String, Object> t4root = new HashMap<String, Object>();
t4root.put("x", 2);
t4root.put("y", "medium");

引用

<1>if, else, elseif:
<#if x == 1>
  x is 1
<#elseif x == 2>
  x is 2
<#elseif x == 3>
  x is 3
<#elseif x == 4>
  x is 4
<#else>
  x is not 1 nor 2 nor 3 nor 4
</#if>

<2>switch, case, default, break:
<#switch y>
  <#case "small">
     This will be processed if it is small
     <#break>
  <#case "medium">
     This will be processed if it is medium
     <#break>
  <#case "large">
     This will be processed if it is large
     <#break>
  <#default>
     This will be processed if it is neither
</#switch>

<3>list, break:
<#assign seq = ["winter", "spring", "summer", "autumn"]>
<#list seq as x>
  ${x_index + 1}. ${x}<#if x_has_next>,</#if>
</#list>

5、自定义函数

引用

<#function fact n>
  <#if n == 0>
    <#return 1 />
  <#else>
    <#return fact(n - 1) * n />
  </#if>
</#function>

<#list 0..10 as i>
  ${i}! => ${fact(i)}
</#list>

6、定义变量

引用

<#-- 1、本地变量 -->[BR]
<#function partg n lst>
  <#local ans = []>
  <#list lst as x>
    <#if (x >= n)>
      <#local ans = ans + [x]>
    </#if>
  </#list>
  <#return ans>
</#function>

<#assign ls = [10, 2, 4, 5, 8, 1, 3]>
<#list partg(4, ls) as x>${x} </#list>

<#-- 2、变量域测试 -->[BR]
<#macro test>
    03. ${x}
    <#global x = "global2">
    04. ${x}
    <#assign x = "assign2">
    05. ${x}
    <#local x = "local1">
    06. ${x}
    <#list ["循环1"] as x>
        07. ${x}
        <#local x = "local2">
        08. ${x}
        <#assign x = "assign3">
        09. ${x}
    </#list>
    10. ${x}
</#macro>

<#global x = "global1" />
01. ${x}
<#assign x = "assign1" />
02. ${x}
<@test />
11. ${x}

7、定义宏macro

引用

<#-- 1、无参数 -->[BR]
<#macro greet>
Welcome!
</#macro>

<@greet />

<#-- 2、有参数 -->[BR]
<#macro greet user>
${user}, Welcome!
</#macro>

<@greet user="RenSanNing"/>

<#-- 3、有多个参数 -->[BR]
<#macro table cols rows>
  <table>
    <#list 1..rows as row>
      <tr>
        <#list 1..cols as col>
          <td>${row}, ${col}</td>
        </#list>
      </tr>
    </#list>
  </table>
</#macro>

<@table cols=3 rows=2 />

<#-- 4、中间跳出 -->[BR]
<#macro out>
  显示文字
  <#return>
  不显示文字
</#macro>

<@out />

<#-- 5、嵌套 -->[BR]
<#macro lprint lst>
  <#list lst as item>
  ・${item}<#nested item />
  </#list>
</#macro>

<@lprint 1..3; x>^2 = ${x * x}</@lprint>
<@lprint 1..3; x>^3 = ${x * x * x}</@lprint>
<@lprint ["Let's go", "to the", "land of Medetai"] />

8、include

引用

<#include "T108include.ftl">
${url}
<@greet name="rensanning" />

T108include.ftl

引用

<#macro greet name>
${name}, Welcome!
</#macro>

<#assign url="http://www.baidu.com/">

9、名字空间

引用

<#import "T109include.ftl" as my>
<#assign url="http://www.google.com/">

${my.url}
<@my.greet name="rensanning" />

${url}

T109include.ftl

引用

<#macro greet name>
${name}, Welcome!
</#macro>

<#assign url="http://www.baidu.com/">

10、自定义指令Directive

public class SystemDateDirective implements TemplateDirectiveModel {
	
	public void execute(Environment env, Map params, TemplateModel[] loopVars,
			TemplateDirectiveBody body) throws TemplateException, IOException {
		Calendar cal = Calendar.getInstance();
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
		env.getOut().append(sdf.format(cal.getTime()));
	}

}

public class TextCutDirective implements TemplateDirectiveModel {
	public static final String PARAM_S = "s";
	public static final String PARAM_LEN = "len";
	public static final String PARAM_APPEND = "append";

	@SuppressWarnings("unchecked")
	public void execute(Environment env, Map params, TemplateModel[] loopVars,
			TemplateDirectiveBody body) throws TemplateException, IOException {
		String s = getString(PARAM_S, params);
		Integer len = getInt(PARAM_LEN, params);
		String append = getString(PARAM_APPEND, params);
		if (s != null) {
			Writer out = env.getOut();
			if (len != null) {
				out.append(textCut(s, len, append));
			} else {
				out.append(s);
			}
		}
	}
      
        ....

Map<String, Object> t10root = new HashMap<String, Object>();
t10root.put("systemdate", new SystemDateDirective());
t10root.put("text_cut", new TextCutDirective());

引用

<@systemdate/>

<@text_cut s="汉字汉字汉字汉字汉字汉字汉字汉字汉字汉字" len=10 append="..."/>