转载自： http://www.blogjava.net/sxyx2008/archive/2010/11/11/337799.html

velocity使用基本来说比较简单，但在加载模板时老出问题，很多初学者经常会遇到找不到模板这种异常。本文就针对目前常用的三种模板加载方式做以说明。
其工程目录结构大致为：

一、velocity默认的加载方式(文件加载方式)

package com.velocity.test;import java.io.StringWriter;
import java.util.Properties;import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.VelocityEngine;/*** 从文件中加载模板文件,即velocity默认的模板文件加载方式* @author welcome**/
public class LoaderFromFile {public static void main(String[] args) throws Exception{//初始化参数Properties properties=new Properties();//设置velocity资源加载方式为fileproperties.setProperty("resource.loader", "file");//设置velocity资源加载方式为file时的处理类properties.setProperty("file.resource.loader.class", "org.apache.velocity.runtime.resource.loader.FileResourceLoader");//实例化一个VelocityEngine对象VelocityEngine velocityEngine=new VelocityEngine(properties);//实例化一个VelocityContextVelocityContext context=new VelocityContext();//向VelocityContext中放入键值context.put("username", "张三");context.put("password", "123456789");context.put("age", "20");context.put("address", "陕西西安"); context.put("blog", "http://blogjava.net/sxyx2008");//实例化一个StringWriterStringWriter writer=new StringWriter();//从vm目录下加载hello.vm模板,在eclipse工程中该vm目录与src目录平级velocityEngine.mergeTemplate("vm/hello.vm", "gbk", context, writer);System.out.println(writer.toString());}
}

二、从类路径加载模板文件

package com.velocity.test;import java.io.StringWriter;
import java.util.Properties;import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.VelocityEngine;/*** 从class(类路径)中加载模板文件* @author welcome**/
public class LoaderFromClass {public static void main(String[] args) throws Exception{//初始化参数Properties properties=new Properties();//设置velocity资源加载方式为classproperties.setProperty("resource.loader", "class");//设置velocity资源加载方式为file时的处理类properties.setProperty("class.resource.loader.class", "org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader");//实例化一个VelocityEngine对象VelocityEngine velocityEngine=new VelocityEngine(properties);//实例化一个VelocityContextVelocityContext context=new VelocityContext();//向VelocityContext中放入键值context.put("username", "张三");context.put("password", "123456789");context.put("age", "20");context.put("address", "陕西西安"); context.put("blog", "http://blogjava.net/sxyx2008");//实例化一个StringWriterStringWriter writer=new StringWriter();//从src目录下加载hello.vm模板//假若在com.velocity.test包下有一个hello.vm文件,那么加载路径为com/velocity/test/hello.vmvelocityEngine.mergeTemplate("com/velocity/test/hello.vm", "gbk", context, writer);//velocityEngine.mergeTemplate("hello.vm", "gbk", context, writer);System.out.println(writer.toString());}
}

三、从jar文件中加载模板文件

package com.velocity.test;import java.io.StringWriter;
import java.util.Properties;import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.VelocityEngine;/*** 从jar文件中加载模板文件* @author welcome**/
public class LoaderFromJar {public static void main(String[] args) throws Exception{//初始化参数Properties properties=new Properties();//设置velocity资源加载方式为jarproperties.setProperty("resource.loader", "jar");//设置velocity资源加载方式为file时的处理类properties.setProperty("jar.resource.loader.class", "org.apache.velocity.runtime.resource.loader.JarResourceLoader");//设置jar包所在的位置properties.setProperty("jar.resource.loader.path", "jar:file:WebRoot/WEB-INF/lib/vm.jar");//实例化一个VelocityEngine对象VelocityEngine velocityEngine=new VelocityEngine(properties);//实例化一个VelocityContextVelocityContext context=new VelocityContext();//向VelocityContext中放入键值context.put("username", "张三");context.put("password", "123456789");context.put("age", "20");context.put("address", "陕西西安"); context.put("blog", "http://blogjava.net/sxyx2008");//实例化一个StringWriterStringWriter writer=new StringWriter();//从/WebRoot/WEB-INF/lib/vm.jar中加载hello.vm模板  vm.jar的目录结构为vm/hello.vmvelocityEngine.mergeTemplate("vm/hello.vm", "gbk", context, writer);System.out.println(writer.toString());}
}