使用AjaxFileUpload组件结合Struts2异步上传需要添加如下文件：

ajaxfileupload.js

jquery-x.x.x-min.js

struts2相关jar包

AjaxFileUpload组件下载连接：http://download.csdn.net/detail/yangfuqian/4337967

具体实现代码：

服务端：

package com.tenghu.action.upload;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import javax.servlet.http.HttpServletRequest;

import org.apache.struts2.ServletActionContext;
import com.opensymphony.xwork2.ActionSupport;
/**
 * 文件上传Action
 * @author xiaohu
 *
 */
public class FileUpload extends ActionSupport{
	private String name;
	//封装上传文件域的属性
	private File file;
	//封装上传文件类型的属性
	private String fileContentType;
	//封装上传文件名的属性
	private String fileFileName;
	//提示信息
	private String json_message;
	
	private String JSON_MESSAGE="json_message";
	
	@Override
	public String execute() throws Exception {
		try {
			//设置文件保存目录
			String saveDir=getRootPath()+"/images";
			File saveFile=new File(saveDir);
			//判断
			if(!saveFile.exists()){
				saveFile.mkdirs();
			}
			//时间戳
			String timeStr="zycs"+System.currentTimeMillis();
			//获取文件后缀
			String fileSuffix=fileFileName.substring(fileFileName.indexOf("."));
			//拼接文件名
			String fileName=timeStr+fileSuffix;
			//创建文件输出流对象
			OutputStream fos=new FileOutputStream(saveDir+"/"+fileName);
			//创建文件输入流对象
			InputStream fis=new FileInputStream(file);
			//创建缓冲数组
			byte[] buffer=new byte[1024];
			int len=0;
			//从输入流中将数据写入到输出流中
			while((len=fis.read(buffer))!=-1){
				//写入
				fos.write(buffer,0,len);
			}
			//关闭资源
			fis.close();
			fos.close();
			//上传成功地址
			String successPath=getUrl()+"/images/"+fileName;
			json_message="{\"result\":1,\"message\":\""+successPath+"\"}";
		} catch (Exception e) {
			e.printStackTrace();
			json_message="{\"result\":0}";
		}
		return JSON_MESSAGE;
	}
	/**
	 * 返回服务器http地址
	 * @return
	 */
	private String getUrl(){
		HttpServletRequest request=ServletActionContext.getRequest();
		return "http://"+request.getRemoteHost()+request.getContextPath();
	}
	
	/**
	 * 获取项目根目录
	 * @return
	 */
	private String getRootPath(){
		String filePath = Thread.currentThread().getContextClassLoader()
				.getResource("").toString();
		if (filePath.toLowerCase().indexOf("file:") > -1) {
			filePath = filePath.substring(6, filePath.length());
		}
		if (filePath.toLowerCase().indexOf("classes") > -1) {
			filePath = filePath.replaceAll("/classes", "");
		}
		if (filePath.toLowerCase().indexOf("web-inf") > -1) {
			filePath = filePath.substring(0, filePath.length() - 9);
		}
		if (System.getProperty("os.name").toLowerCase().indexOf("window") < 0) {
			filePath = "/" + filePath;
		}

		if (filePath.endsWith("/"))
			filePath = filePath.substring(0, filePath.length() - 1);

		return filePath;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public File getFile() {
		return file;
	}

	public void setFile(File file) {
		this.file = file;
	}

	public String getFileContentType() {
		return fileContentType;
	}

	public String getJson_message() {
		return json_message;
	}
	public void setJson_message(String jsonMessage) {
		json_message = jsonMessage;
	}
	public void setFileContentType(String fileContentType) {
		this.fileContentType = fileContentType;
	}

	public String getFileFileName() {
		return fileFileName;
	}

	public void setFileFileName(String fileFileName) {
		this.fileFileName = fileFileName;
	}
}