struts2文件下载

<action name="test" class="com.TestAction" method="importToFile">
<result name="success" type="stream">
<param name="contentType">unknown</param>
<param name="inputName">downloadFile</param> <!--下载文件的文件流名称，在action中需要给它一个get方法返回下载文件的流-->
<param name="contentDisposition">attachment;filename="${downloadFileName}"</param>
<param name="bufferSize">4096</param>
</result>
</action>

public InputStream getDownloadFile() throws InvalidResultSetAccessException, IOException, SQLException {
String path = request.getSession().getServletContext().getRealPath("/temp");
File dir = new File(path);
if (!dir.exists())
dir.mkdir();
parent_code = request.getParameter("parent_code");
String fileName = "shopbarcode_"+parent_code+".txt";
File file = new File(dir,fileName);
FileWriter writer = new FileWriter(file);
DB db = new DB();
writeToFile(db, writer, parent_code);
writer.close();
return ServletActionContext.getServletContext().getResourceAsStream("/temp/"+fileName);
}

public String importToFile() {
setDownloadFileName("test.txt");
return SUCCESS;
}