Java操作FreeMarker模板引擎的基本用法示例小結(jié)

更新時(shí)間：2016年02月26日 09:30:22 作者：rensanning

這篇文章主要介紹了Java操作FreeMarker模板引擎的基本用法示例小結(jié),FreeMarker本身由Java寫成,用模板來(lái)生成文本輸出,需要的朋友可以參考下

FreeMarker 是一個(gè)采用 Java 開發(fā)的模版引擎，是一個(gè)基于模版生成文本的通用工具。它被設(shè)計(jì)用來(lái)生成 HTML Web 頁(yè)面，特別是基于 MVC 模式的應(yīng)用程序。雖然使用FreeMarker需要具有一些編程的能力，但通常由 Java 程序準(zhǔn)備要顯示的數(shù)據(jù)，由 FreeMarker 生成頁(yè)面，并通過(guò)模板顯示準(zhǔn)備的數(shù)據(jù)。
http://freemarker.org/

public void process(String template, Map<String, ?> data) throws Exception { 
  Configuration cfg = new Configuration(); 
  cfg.setDirectoryForTemplateLoading(new File("ftl")); 
  cfg.setObjectWrapper(new DefaultObjectWrapper()); 
   
  //設(shè)置字符集 
  cfg.setDefaultEncoding("UTF-8"); 
   
  //設(shè)置尖括號(hào)語(yǔ)法和方括號(hào)語(yǔ)法,默認(rèn)是自動(dòng)檢測(cè)語(yǔ)法 
  // 自動(dòng) AUTO_DETECT_TAG_SYNTAX 
  // 尖括號(hào) ANGLE_BRACKET_TAG_SYNTAX 
  // 方括號(hào) 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(); 
}

0、使用freemarker制作HelloWord web頁(yè)面
新建一個(gè)WEB工程，并導(dǎo)入freemarker.jar，在WEB-INF下新建文件夾templates用于存放模版文件，在templates下新建test.ftl，這是示例模版文件。內(nèi)容就是HTML內(nèi)容，里面帶有一個(gè)標(biāo)記符，用于將來(lái)進(jìn)行變量替換，內(nèi)容如下：

<html> 
 <head> 
    <title>freemarker測(cè)試</title> 
  </head> 
  <body> 
    <h1>${message},${name}</h1> 
  </body> 
</html>

新建一個(gè)Servlet，用于請(qǐng)求設(shè)置變量，并處理模版的輸出：

package com.test.servlet; 
import java.io.IOException; 
import java.io.Writer; 
import java.util.HashMap; 
import java.util.Map; 
import javax.servlet.ServletException; 
import javax.servlet.http.HttpServlet; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
import freemarker.template.Configuration; 
import freemarker.template.Template; 
import freemarker.template.TemplateException; 
@SuppressWarnings("serial") 
public class HelloFreeMarkerServlet extends HttpServlet { 
  // 負(fù)責(zé)管理FreeMarker模板的Configuration實(shí)例 
  private Configuration cfg = null; 
  public void init() throws ServletException { 
    // 創(chuàng)建一個(gè)FreeMarker實(shí)例 
    cfg = new Configuration(); 
    // 指定FreeMarker模板文件的位置 
    cfg.setServletContextForTemplateLoading(getServletContext(), 
        "/WEB-INF/templates"); 
  } 
  @SuppressWarnings("unchecked") 
  public void doPost(HttpServletRequest request, HttpServletResponse response) 
      throws ServletException, IOException { 
    // 建立數(shù)據(jù)模型 
    Map root = new HashMap(); 
    root.put("message", "hello world"); 
    root.put("name", "java小強(qiáng)"); 
    // 獲取模板文件 
    Template t = cfg.getTemplate("test.ftl"); 
    // 使用模板文件的Charset作為本頁(yè)面的charset 
    // 使用text/html MIME-type 
    response.setContentType("text/html; charset=" + t.getEncoding()); 
    Writer out = response.getWriter(); 
    // 合并數(shù)據(jù)模型和模板，并將結(jié)果輸出到out中 
    try { 
      t.process(root, out); // 往模板里寫數(shù)據(jù) 
    } catch (TemplateException e) { 
      e.printStackTrace(); 
    } 
  } 
  public void doGet(HttpServletRequest request, HttpServletResponse response) 
      throws ServletException, IOException { 
    doPost(request, response); 
  } 
  public void destroy() { 
    super.destroy(); 
  } 
}

注意要在你的web.xml中配置該Servlet：

<?xml version="1.0" encoding="UTF-8"?> 
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xsi:schemaLocation="http://java.sun.com/xml/ns/javaee  
  http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> 
  <servlet> 
    <servlet-name>hello</servlet-name> 
    <servlet-class> 
      com.test.servlet.HelloFreeMarkerServlet 
    </servlet-class> 
  </servlet> 
  <servlet-mapping> 
    <servlet-name>hello</servlet-name> 
    <url-pattern>/hello</url-pattern> 
  </servlet-mapping> 
  <welcome-file-list> 
    <welcome-file>index.jsp</welcome-file> 
  </welcome-file-list> 
</web-app>

為了方便測(cè)試，訪問(wèn)工程直接跳轉(zhuǎn)到Servlet，對(duì)主頁(yè)index.jsp做一個(gè)簡(jiǎn)單修改：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> 
<% 
String path = request.getContextPath(); 
String basePath = request.getScheme()+"://"+request.getServerName() 
+":"+request.getServerPort()+path+"/"; 
%> 
<html> 
 <body> 
  <% 
  String mypath = "hello"; 
  response.sendRedirect(basePath + mypath); 
  %> 
 </body> 
</html>

部署工程到Tomcat，啟動(dòng)并訪問(wèn)http://localhost:8080/f ，這里我建立的工程名稱就是 f 。

1、計(jì)算式

<#-- 1、算術(shù)運(yùn)算 -->[BR] 
${3 + 4} 

<#-- 2、內(nèi)建函數(shù) -->[BR] 
${"rensanning"?upper_case}

2、輸出一個(gè)值

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

${user}, Welcome!

3、輸出一個(gè)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); 

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

4、邏輯判斷（IF,SWITCH)

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

<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、自定義函數(shù)

<#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、定義變量

<#-- 1、本地變量 -->[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、變量域測(cè)試 -->[BR] 
<#macro test> 
  03. ${x} 
  <#global x = "global2"> 
  04. ${x} 
  <#assign x = "assign2"> 
  05. ${x} 
  <#local x = "local1"> 
  06. ${x} 
  <#list ["循環(huán)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、定義宏macro

<#-- 1、無(wú)參數(shù) -->[BR] 
<#macro greet> 
Welcome! 
</#macro> 

<@greet /> 

<#-- 2、有參數(shù) -->[BR] 
<#macro greet user> 
${user}, Welcome! 
</#macro> 

<@greet user="RenSanNing"/> 

<#-- 3、有多個(gè)參數(shù) -->[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、中間跳出 -->[BR] 
<#macro out> 
 顯示文字 
 <#return> 
 不顯示文字 
</#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

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

T108include.ftl

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

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

9、名字空間

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

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

${url}

T109include.ftl

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

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

10、自定義指令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());

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