上传文件到阿里云，项目架构限制，用servlet方法上传，但是现在的文件不对，处理代码如下：

package com.twsz.creative.lucy.controller;

import java.io.DataInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.net.HttpRetryException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;

import org.springframework.stereotype.Controller;

import com.howie.transitionService.UploadService;

@Controller
public class UploadServlet extends HttpServlet {

private UploadService uploadService;

public void service(HttpServletRequest request,HttpServletResponse response) throws HttpRetryException,IOException, ServletException{
    uploadService = new UploadService();
    byte[] body = readBody(request);
    String textBody = new String(body,"UTF-8");
    String fileName = getFileName(textBody);    //获取到文件名
    int[] position = getFilePosition(request,textBody);
    int length = position[1] - position[0];
    byte[] bytes = new byte[length+1];
    for(int i=0;i < length;i++){
        bytes[i] = body[position[0]];
        position[0] +=1;
    }
    //System.arraycopy(body, position[0], bytes, 0, position[1]-position[0]+1); 
    /* 截取的时候老是出现数组越界的情况
     * byte[] bytes = subBytes(body,getFilePosition(request,textBody)[0],
            getFilePosition(request,textBody)[1]);*/
    System.out.println(fileName);
    System.out.println("原byte流："+body);
    System.out.println("文件byte流：");
    System.out.println(bytes);
    String url = uploadService.uploadFile(bytes, fileName);
    System.out.println(url);
}

/*private byte[] requestToByte(HttpServletRequest request) throws IOException, ServletException{
    Part part = request.getPart("myfile");
    String disposition = part.getHeader("content-dispositon");
    String fileName = disposition.substring(disposition.lastIndexOf("=")+2,disposition.length()-1);
    InputStream is = part.getInputStream();
    String path = getServletContext().getRealPath("/upload");
    FileOutputStream out = new FileOutputStream(path+fileName);
    byte[] buf = new byte[10*1024*1024];
    int len = 0;
    while((len=is.read(buf)) != -1){
        out.write(buf, 0, len);
    }
    out.close();
    return buf;
}*/

//将request转化成byte[]格式
private byte[] readBody(HttpServletRequest request) throws IOException{
    int formDataLength = request.getContentLength();
    DataInputStream dataStream = new DataInputStream(request.getInputStream());
    byte body[] = new byte[formDataLength];
    int totalBytes = 0;
    while(totalBytes < formDataLength){
        int bytes = dataStream.read(body, totalBytes, formDataLength);
        totalBytes += bytes;
    }
    return body;
}

//返回文件名
private String getFileName(String repBody){
    String fileName = repBody.substring(repBody.indexOf("filename=\"")+10);
    fileName = fileName.substring(0,fileName.indexOf("\n"));
    fileName = fileName.substring(fileName.lastIndexOf("\\")+1,
            fileName.indexOf("\""));
    return fileName;
} 

//从byte[]流中去除http头部，截取文件的部分
private byte[] subBytes(byte[] src,int begin,int end){
    int length  = end-begin + 1;
    byte[] bytes = new byte[length];
    System.arraycopy(src, begin, bytes, 0, length-1);
    return bytes;
}

private int[] getFilePosition(HttpServletRequest request,String textBody) throws UnsupportedEncodingException{
    String contentType = request.getContentType();
    String boundaryText = contentType.substring(
            contentType.lastIndexOf("=")+1,contentType.length());
    int pos = textBody.indexOf("filename=\"");
    System.out.println(textBody.charAt(pos));
    pos = textBody.indexOf("\n", pos) + 1;
    System.out.println(textBody.charAt(pos));
    pos = textBody.indexOf("\n", pos) + 1;
    System.out.println(textBody.charAt(pos));
    pos = textBody.indexOf("\n", pos) + 1;
    System.out.println(textBody.charAt(pos));
    int boundaryLoc = textBody.indexOf(boundaryText, pos) - 4;
    System.out.println(textBody.charAt(boundaryLoc));
    int begin = ((textBody.substring(0,pos)).getBytes("utf-8")).length;
    int end = ((textBody.substring(0,boundaryLoc)).getBytes("utf-8")).length;
    int[] position = new int[2];        //将文件的位置存放在position里
    position[0] = begin;
    position[1] = end;
    return position;
}

}

https://yq.aliyun.com/articles/45248

谢谢楼上回答，链接里的方法看过，大部分也是用的这个！现在问题是在request里面截取的文件部分不太对，图片上传成功之后拿到链接是一片黑色