Velocity路径问题

package velocity.action;
import java.io.IOException;
import java.io.StringWriter;
import java.io.Writer;
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.Template;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.Velocity;
import org.apache.velocity.app.VelocityEngine;
import org.apache.velocity.context.Context;
import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.ResourceNotFoundException;
public class LoginAction extends HttpServlet{

private static final long serialVersionUID = 5523228343945982882L;
private VelocityEngine ve;
Context context ;
@Override
public void init() throws ServletException {
	super.init();
	context = new VelocityContext();
	ve = new VelocityEngine();//得到velocity引擎
	try {
	    Properties prop = new Properties();// 设置vm模板的装载路径
	    String path = this.getServletContext().getRealPath("/");
	    prop.setProperty(Velocity.FILE_RESOURCE_LOADER_PATH, path); 
		ve.init(prop);//初始化配置文件
	} catch (Exception e) {
		e.printStackTrace();
	}
}
@Override
	protected void service(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
	String vm = "/WebRoot/velocity/login.vm";
	String out = "login.htm";
	Template tpl = null;
	try {
		tpl = ve.getTemplate(vm);
		Writer writer = resp.getWriter();
		context.put("name", "lele");
		tpl.merge(context, writer);
		writer.write(out);
		System.out.println(out);
	} catch (Exception e) {
		e.printStackTrace();
	}
	}
public static void main(String[] args) throws ResourceNotFoundException, ParseErrorException, Exception {
	VelocityEngine v = new VelocityEngine();
	v.init();
	System.out.println(Thread.currentThread().getContextClassLoader().getResource(".").getPath());
	Template tpl = v.getTemplate("/WebRoot/velocity/login.vm");
	Context context = new VelocityContext();
	context.put("name", "liujq");
	StringWriter sw = new StringWriter();
	tpl.merge(context, sw);

	System.out.println(sw.toString());
}
}

问题：

org.apache.velocity.exception.ResourceNotFoundException: Unable to find resource ""/WebRoot/velocity/login.vm""
	at org.apache.velocity.runtime.resource.ResourceManagerImpl.loadResource(ResourceManagerImpl.java:458)
	at org.apache.velocity.runtime.resource.ResourceManagerImpl.getResource(ResourceManagerImpl.java:341)
	at org.apache.velocity.runtime.RuntimeInstance.getTemplate(RuntimeInstance.java:831)
	at org.apache.velocity.runtime.RuntimeInstance.getTemplate(RuntimeInstance.java:813)
	at org.apache.velocity.app.VelocityEngine.getTemplate(VelocityEngine.java:470)
	at velocity.action.LoginAction.service(LoginAction.java:49)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:261)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:581)
	at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
	at java.lang.Thread.run(Thread.java:724)

该类假如运行main方法，没有问题
配置路径

请高手们帮忙解决一下。
谢谢