浅谈图片上传利用request.getInputStream()获取文件流时遇到的问题

int length = request.getContentLength();//获取请求参数长度。
byte[] bytes = new byte[length];//定义数组，长度为请求参数的长度
DataInputStream dis = new DataInputStream(request.getInputStream);//获取请求内容，转成数据输入流
int readcount = 0;//定义输入流读取数
while(readcount < length){
 int aa= dis.read(bytes,readcount,length); //读取输入流，放入bytes数组，返回每次读取的数量
 readcount = aa + readcount; //下一次的读取开始从readcount开始
}
//读完之后bytes就是输入流的字节数组，将其转为字符串就能看到
String bb = new String(bytes,"UTF-8");

DataInputStream dis = new DataInputStream(request.getInputStream());
ByteArrayOutputStream baot = new ByteArrayOutputStream();
byte[] bytes = new byte[1024]; //定义一个数组 用来读取
int n = 0;//每次读取输入流的量
while((n=dis.read(bytes))!=-1){
 baot.write(bytes); //将读取的字节流写入字节输出流 
}
byte[] outbyte = boat.toByteArray();//将字节输出流转为自己数组。
String bb = new String(outbyte,"UTF-8");

/**
  * 取得图片数据
  *
  * @param requestData
  * @param contentType
  * @return
  * @throws IOException
  */
 private byte[] getImgData(byte[] requestData, String contentType)
   throws IOException {
  String txtBody = new String(requestData, "GBK");
  if (!txtBody.contains("image/jpg") && !txtBody.contains("image/jpeg")&& !txtBody.contains("jpg")) {
   return null;
  }
  String boundarytext = contentType.substring(
    contentType.lastIndexOf("=") + 1, contentType.length());
  // 取得实际上传文件的起始与结束位置
  int pos = txtBody.indexOf("filename=\"");
  pos = txtBody.indexOf("\n", pos) + 1;
  pos = txtBody.indexOf("\n", pos) + 1;
  pos = txtBody.indexOf("\n", pos) + 1;
  // 文件描述信息后就文件内容，直到为文件边界为止，从pos开始找边界
  int boundaryLoc = txtBody.indexOf(boundarytext, pos) - 4;
  ByteArrayOutputStream realdatas = null;
  try {
   int begin = ((txtBody.substring(0, pos)).getBytes("GBK")).length;
   int end = ((txtBody.substring(begin, boundaryLoc)).getBytes("GBK")).length;
   realdatas = new ByteArrayOutputStream();
   realdatas.write(requestData, begin, end); 
   return realdatas.toByteArray();
  } finally {
   if (null != realdatas) {
    try {
     realdatas.close();
    } catch (IOException e) {
     logger.error("处理上传图片数据错误：", e);
    }
   }
  }
 }

OutputStream os = response.getOutputStream();
os.write(bytes);