配置FileService映射:

dwr.xml

<create creator="new">
      <param name="class" value="com.demo.service.FileService"/>
    </create>


FileService: 

package com.demo.service;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;

import org.apache.commons.io.FileUtils;
import org.apache.commons.io.FilenameUtils;
import org.directwebremoting.WebContext;
import org.directwebremoting.WebContextFactory;

public class FileService {
	public String upload(InputStream inputStream,String fileName) throws IOException{
		String tempFileName=FilenameUtils.getName(fileName);
		String path=getRealPath("upload");
		File file=new File(path+File.separator+tempFileName);
		FileUtils.copyInputStreamToFile(inputStream, file);
		return file.getPath();
	}
	public String getRealPath(String dir){
		WebContext context=WebContextFactory.get();
		return context.getSession().getServletContext().getRealPath(dir);
	}
}


upload.jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>文件上传</title>
<script type="text/javascript" src="<%=request.getContextPath()%>/dwr/engine.js"></script>
<script type="text/javascript" src="<%=request.getContextPath()%>/dwr/util.js"></script>
<script type="text/javascript" src="<%=request.getContextPath()%>/dwr/interface/FileService.js"></script>
<script type="text/javascript">
	function upload(){
		var file=dwr.util.getValue("file");
		FileService.upload(file,file.value,function(result){
			alert(result);
		});
	}
</script>
</head>
<body>
附件:<input type="file" id="file" name="file"><br/>
<button onclick="upload();">上传</button>
</body>
</html>


结果:

附件已上传到upload目录中