用Action下载文件

package com.eaoa.uc.attachment.action;

import java.io.InputStream;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.lang.StringUtils;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;

import com.eaoa.base.EABaseAction;
import com.eaoa.query.PubAttachmentQuery;
import com.eaoa.vo.PubAttachment;
import com.stony.core.util.CoreUtils;

/**
* Find a attachment from table "EAPT_ATTACHMENT" by attachmentno, and show it on page. 
* @author zhenglun.zhou
*
*/
public class AttachmentViewAction extends EABaseAction {

    protected ActionForward doWork(ActionMapping mapping, ActionForm form,
            HttpServletRequest request, HttpServletResponse response) {
   
    String attachmentnostr = request.getParameter("attachmentno");
    if(StringUtils.isBlank(attachmentnostr))
    return null;
   
    Long attachmentno = CoreUtils.parseLong(attachmentnostr);  
    PubAttachment attachment = PubAttachmentQuery.loadByNo(attachmentno);

//扩展名和文件名
String extname = attachment.getExtendname().toLowerCase();
String filename = attachment.getAttachmentname();

//设置response
setIsStream(response);
response.reset(); //清除response的buffer
if (extname.indexOf("bmp,jpeg,gif") != -1) {
response.setContentType("image/"+extname);
} else if ("jpg".equals(extname)) {
response.setContentType("image/jpeg");
} else if ("xls".equals(extname)) {
response.setContentType("application/vnd.ms-excel");
response.setHeader("Content-disposition", "attachment; filename="+filename);
} else if ("doc".equals(extname)) {
response.setContentType("application/msword; charset=gb2312");
response.setHeader("Content-disposition", "attachment; filename="+filename);
} else if ("ppt".equals(extname)) {
response.setContentType("application/vnd.ms-powerpoint; charset=gb2312");
response.setHeader("Content-disposition", "attachment; filename="+filename);
}else{
response.setHeader("Content-disposition", "attachment; filename="+filename);
}

//输出流
InputStream ins = null;
try {
ins = attachment.getContent().getBinaryStream();
ServletOutputStream outs = response.getOutputStream();
int blobsize = (int) attachment.getContent().length();
byte[] blobbytes = new byte[blobsize];
int bytesRead = 0;
while ((bytesRead = ins.read(blobbytes)) != -1) {
outs.write(blobbytes, 0, bytesRead);
}
ins.close();
outs.flush();
outs.close();
} catch (Exception e) {
}
return null;     
    }
}