FreeMarker概述
•FreeMarker是一個模板引擎，一個基於模板生成文本輸出的通用工具，使用純Java編寫
•Template + data model = output
•
•Hello world
•FreeMarkerTest.java
import java.io.StringWriter;import java.util.HashMap;import java.util.Locale; import freemarker.template.Configuration;import freemarker.template.Template; publicclass FreeMarkerTest { publicstaticvoid main(String[] args){ FreeMarkerTest test = new FreeMarkerTest(); test.sayHello("Hermit"); } publicvoid sayHello(String name){ Configuration freemarkerCfg = new Configuration(); freemarkerCfg.setClassForTemplateLoading(this.getClass(), "/"); freemarkerCfg.setEncoding(Locale.getDefault(), "UTF-8"); Template template; Locale.setDefault(Locale.ENGLISH); try{ template = freemarkerCfg.getTemplate("Hello.ftl"); template.setEncoding("UTF-8"); HashMap root = newHashMap(); root.put("user", name); StringWriter writer = newStringWriter(); template.process(root, writer); System.out.println(writer.toString()); }catch(Exception e){ e.printStackTrace(); }} } •Hello.ftl
Hello ${user}! •輸出
Hello Hermit!
空值的處理
在我們的程序中難免會碰到值爲空的時候，如果用一個空值直接去替換模板中的標記，freemarker會毫不猶豫的拋出異常，並把錯誤信息直接寫到輸出結果裏。爲了對付這種情況我們有兩種寫法
•模板
Hello ${user!}!Hello ${user?if_exists}Hello ${user!'your name'}!Hello ${user?default('your name')} •程序
test.sayHello(null); •輸出
Hello !Hello your name!Hello Hello your name freemarker國際化模板
freemarker支持多語言國際化，只要把模板名稱按照java資源文件的寫法就可以了,也就是name_語言_國家地區.ftl 如果找不到對應的語言，就會用默認語言的模板。
•程序
import java.io.StringWriter;import java.util.HashMap;import java.util.Locale; import freemarker.template.Configuration;import freemarker.template.Template; publicclass FreeMarkerTest { publicstaticvoid main(String[] args){ FreeMarkerTest test = new FreeMarkerTest(); test.sayHello("hermit",Locale.CHINA); test.sayHello("hermit",Locale.ENGLISH); } publicvoid sayHello(String name,Locale locale){ Configuration freemarkerCfg = new Configuration(); freemarkerCfg.setClassForTemplateLoading(this.getClass(), "/"); freemarkerCfg.setEncoding(Locale.getDefault(), "UTF-8"); Template template; Locale.setDefault(Locale.ENGLISH); try{ template = freemarkerCfg.getTemplate("Hello.ftl",locale); template.setEncoding("UTF-8"); HashMap root = newHashMap(); root.put("user", name); StringWriter writer = newStringWriter(); template.process(root, writer); System.out.println(writer.toString()); }catch(Exception e){ e.printStackTrace(); } } } •默認語言模版:Hello.ftl
Hello ${user!}! 中文模版:Hello_zh_CN.ftl 你好 ${user!}!輸出你好 hermit!Hello hermit! 在struts項目中使用freemarker
1、引入freemarker.jar
2、web.xml加入
<!-- FreeMarker view servlet (to replace JSP) --> <servlet><servlet-name>freemarker</servlet-name><servlet-class> freemarker.ext.servlet.FreemarkerServlet </servlet-class> <!-- FreemarkerServlet settings: --> <init-param> <param-name>TemplatePath</param-name> <param-value>/</param-value> </init-param> <init-param> <param-name>NoCache</param-name> <param-value>true</param-value> </init-param> <init-param> <param-name>ContentType</param-name> <param-value>text/html</param-value> </init-param> <!-- FreeMarker settings: --><init-param><param-name>template_update_delay</param-name><param-value>0</param-value><!-- 0 is for development only! Use higher value otherwise. --></init-param><init-param><param-name>default_encoding</param-name><param-value>utf-8</param-value></init-param><init-param><param-name>locale</param-name><param-value>en_US</param-value></init-param><init-param><param-name>number_format</param-name><param-value>0.##########</param-value></init-param> <load-on-startup>1</load-on-startup></servlet> <servlet-mapping><servlet-name>freemarker</servlet-name><url-pattern>*.ftl</url-pattern></servlet-mapping> 3、一個示例頁面
<html><head><title>Say Hello</title><METAHTTP-EQUIV="Content-Type"CONTENT="text/html; charset=utf-8"></head><body><h1>Hello ${user}!</h1></body></html> 我們完全可以用freemarker的模板取代JSP頁面。用freemarker的模板看起更簡潔，可讀性更強。比如現在struts2的UI標籤就是用freemarker做的。
freemarker用struts標籤做國際化
•示例模板
<#assign html =JspTaglibs["/WEB-INF/struts-html.tld"]><#assign bean =JspTaglibs["/WEB-INF/struts-bean.tld"]><#assign logic =JspTaglibs["/WEB-INF/struts-logic.tld"]><html><head><title> FreeMarker Struts Example </title><metahttp-equiv ="Content-type"content ="text/html; charset=utf-8"></ head ><body><@bean.message key ="hello" arg0 ="hermit"/></body></html> 主要是引入標籤的時候要這樣寫：
<#assign html =JspTaglibs["/WEB-INF/struts-html.tld"]> freemarker直接使用資源文件進行多語言國際化
•程序
import java.io.StringWriter;import java.util.HashMap;import java.util.Locale;import java.util.ResourceBundle; import freemarker.ext.beans.BeansWrapper;import freemarker.ext.beans.ResourceBundleModel;import freemarker.template.Configuration;import freemarker.template.Template; publicclass FreeMarkerTest { publicstaticvoid main(String[] args){ FreeMarkerTest test = new FreeMarkerTest(); test.sayHello("hermit",Locale.CHINA); test.sayHello("hermit",Locale.ENGLISH); } publicvoid sayHello(String name,Locale locale){ Configuration freemarkerCfg = new Configuration(); freemarkerCfg.setClassForTemplateLoading(this.getClass(), "/"); freemarkerCfg.setEncoding(Locale.getDefault(), "UTF-8"); Template template; Locale.setDefault(Locale.ENGLISH); try{ template = freemarkerCfg.getTemplate("Hello.ftl"); template.setEncoding("UTF-8"); HashMap root = newHashMap(); root.put("user", name); ResourceBundle RESOURCE_BUNDLE = ResourceBundle.getBundle("ApplicationResources",locale); ResourceBundleModel rsbm = new ResourceBundleModel(RESOURCE_BUNDLE,new BeansWrapper()); root.put("bundle", rsbm); StringWriter writer = newStringWriter(); template.process(root, writer); System.out.println(writer.toString()); }catch(Exception e){ e.printStackTrace(); }} } 模板${bundle("hello","hermit")} 默認語言資源文件 hello=Hello {0}/! 中文資源文件 hello=你好 {0}/!•輸出
你好 hermit!Hello hermit!關鍵的地方就是用ResourceBundleModel把ResourceBundle轉換一下。
常用的2種加載模板的方式
•普通java類根據當前class上下文環境加載模板
cfg.setClassForTemplateLoading(this.getClass(), "/");•在web項目中根據servlet上下文環境加載模板
cfg.setServletContextForTemplateLoading(this.getServlet().getServletContext(), "/");
本篇文章來源於 新技術天空 原文鏈接：http://www.ntsky.com/tech/java/opensource/template/2007-10-20/59e034abc198936c.html