[JavaWeb基础] 020.Velocity 模板引擎简单示例

1.什么是Velocity

一种J2EE的前端模版技术，和JSP，Freemarker差不多，都是用来展示网页内容的。和JSP不同的是velocity只能显示Action中的数据，不能处理数据。不能写java代码，但是可以使用Velocity标记。也就是说把显示代码和后端的JAVA代码分离开来，降低程序的耦合性

2.需要引入哪些Jar包

velocity-1.5.jar,velocity-1.6.2.jar,velocity-tools-2.0.jar,velocity-tools-generic-2.0.jar,velocity-tools-view-2.0.jar

3.编写模板.vm文件

<html>
	<head>
	<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
	</head>
	<body>
		<!-- 页面对变量赋值  -->
		#set( $current = "Velocity22")
		<!-- 输出 -->
		$current is great!  <br/>

		<!-- 输出后台context设置的参数 -->
		$name  <br/>
		
		<!--String循环-->
		#foreach( $elem in $arrList)
    		$elem</br>
		#end
		
		<!--对象循环-->
		#foreach( $elem in $userList)
    		名字:$elem.name 性别:$elem.sex 地址:$elem.address</br>
		#end
	</body>
</html>

4.编写servelet文件

package com.babybus.sdteam.servelet;

import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.Properties;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.Velocity;
import org.apache.velocity.app.VelocityEngine;
import org.apache.velocity.exception.MethodInvocationException;
import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.ResourceNotFoundException;

import com.babybus.sdteam.vo.User;

public class VelocityTemplateServelt extends HttpServlet {

	private static final long serialVersionUID = 1L;

	@Override
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws IOException, ServletException {
		
		// 设置request 和 response 编码,放置乱码
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        
        // 获取页面输出流
        PrintWriter out = response.getWriter(); 
        
        // 创建Properties文件,也可以直接在目录下创建
        Properties properties=new Properties();
        properties.setProperty("resource.loader", "class");
        properties.setProperty("class.resource.loader.class", "org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader");
        properties.setProperty(Velocity.ENCODING_DEFAULT, "UTF-8");
        properties.setProperty(Velocity.INPUT_ENCODING, "UTF-8");
        properties.setProperty(Velocity.OUTPUT_ENCODING, "UTF-8");
        
        // 创建模板引擎
        VelocityEngine velocityEngine = null;
		try {
			velocityEngine = new VelocityEngine(properties);
		} catch (Exception e) {
			e.printStackTrace();
		}
		
		// 创建上下文, 用于存放变量
        VelocityContext context=new VelocityContext();
        context.put("name", "test");
        
        // List(String)
        ArrayList<String> arrList = new ArrayList<String>();
        arrList.add("test01");
        arrList.add("test02");
        arrList.add("test03");
        context.put("arrList", arrList);
        
        // UserList(存放对象List)
        ArrayList<User> userList = new ArrayList<User>();
        userList.add(new User("蔡大三", "男", "南安一中五条巷子"));
        userList.add(new User("马大哈", "男", "红灯区"));
        userList.add(new User("林超",  "女", "下三路"));
        context.put("userList", userList);
        
        // 读取模板文件流
        StringWriter sw = new StringWriter();
        try {
			velocityEngine.mergeTemplate("templates/example.vm", "utf-8", context, sw);
		} catch (ResourceNotFoundException e) {
			e.printStackTrace();
		} catch (ParseErrorException e) {
			e.printStackTrace();
		} catch (MethodInvocationException e) {
			e.printStackTrace();
		} catch (Exception e) {
			e.printStackTrace();
		}
        
        // 输出到页面
        out.println(sw.toString());
    }
}

5.配置web.xml

<?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">
  <display-name></display-name>	
  
  <!--MyVelocity-->
  <servlet>
	   <servlet-name>ve</servlet-name>
	   <servlet-class>com.babybus.sdteam.servelet.VelocityTemplateServelt</servlet-class>
  </servlet>
  <servlet-mapping>
	    <servlet-name>ve</servlet-name>
	    <url-pattern>/ve</url-pattern>
  </servlet-mapping>

  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>

6.输入地址:http://localhost:8080/velocitydemo/ve启动项目

本站文章为 宝宝巴士 SD.Team 原创，转载务必在明显处注明：（作者官方网站：宝宝巴士 )

转载自【宝宝巴士SuperDo团队】 原文链接: http://www.cnblogs.com/superdo/p/4827097.html