下载也是老生常谈的话题 有时候我们下载的比如pdf 直接打开，或者下载的ofd 是一个压缩包。今天正对这个问题 有一种情况会导致这种情况。

• 直接打开的伪代码

  StringBuilder fileName = new StringBuilder();//模拟文件名称
  fileName.append(queryByInvoiceId.getInvoiceCode()).append("_").append(queryByInvoiceId.getInvoiceNum()).append(suf);
  OSSClient ossClient = null;
  InputStream  inputStream = null;
  String key = null;
  ServletOutputStream outputStream = null;
  ossClient = AliyunOSSClientUtil.getOSSClient();
  String key = "aliyunkey";
  inputStream = GetInputStream(ossClient, key);
  try {
    
    
   outputStream = response.getOutputStream();
   int len = 0;
   byte[] buffer = new byte[4096];
   while ((len = inputStream.read(buffer)) != -1) {
    
    
    outputStream.write(buffer, 0, len);
    outputStream.flush();
   }
   response.setCharacterEncoding("UTF-8");
   response.setContentType("application/x-msdownload");//设置下载类型
   response.addHeader("Content-Disposition",
     "attachment;filename=" + fileName);
  } catch (Exception e) {
    
    
   // TODO Auto-generated catch block
   logger.error(e.getMessage(),e);
   
  }finally {
    
    
   try {
    
    
    if(inputStream != null) {
    
    
     inputStream.close();
    }
    if(outputStream != null) {
    
    
     outputStream.close();
    }
   } catch (IOException e) {
    
    
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
  }

• 问题所在

问题所在：其实不难发现代码看似是没有问题，但是在设置response 属性的时候 在 outputStream = response.getOutputStream();获取输出流的时候 还没有设置，导致属性作用不会再输出流体现。知道问题所在 我们就知道我们设置应该是在获取输出流之前设置。

• 最终伪代码

  StringBuilder fileName = new StringBuilder();
  OSSClient ossClient = null;
  InputStream  inputStream = null;
  String key = null;
  ServletOutputStream outputStream = null;
  ossClient = AliyunOSSClientUtil.getOSSClient();
  String key = "aliyunKey";
  inputStream = GetInputStream(ossClient, key);
  try {
    
    
   response.setCharacterEncoding("UTF-8");
   response.setContentType("application/x-msdownload");
   response.addHeader("Content-Disposition",
     "attachment;filename=" + fileName);
   outputStream = response.getOutputStream();
   int len = 0;
   byte[] buffer = new byte[4096];
   while ((len = inputStream.read(buffer)) != -1) {
    
    
    outputStream.write(buffer, 0, len);
    outputStream.flush();
   }
  } catch (Exception e) {
    
    
   // TODO Auto-generated catch block
   logger.error(e.getMessage(),e);
  }finally {
    
    
   try {
    
    
    if(inputStream != null) {
    
    
     inputStream.close();
    }
    if(outputStream != null) {
    
    
     outputStream.close();
    }
   } catch (IOException e) {
    
    
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
  }