struts2上传下载，下载非txt类型文档后台报错，但文件成功下载了 ?报错

下载非txt类型文档时后台报了个异常：（下载txt不报异常）
java.lang.IllegalStateException: Cannot call sendError() after the response has been committed
at org.apache.catalina.connector.ResponseFacade.sendError(ResponseFacade.java:451)
at org.apache.struts2.dispatcher.Dispatcher.sendError(Dispatcher.java:770)
请问怎么在下载其他非txt类型文件时不报错。谢谢。

我在downloadAction里是这样获取InputStream的：
public InputStream getDownLoadFile() throws Exception {
fileName = new String(fileName.getBytes("ISO8859-1"), "UTF-8");
return new FileInputStream(new File(path + fileName)); //path + fileName(绝对路径下的文件)
}