http协议文件与数据上传、及上传图片io流错误

package com.smartdoer.utils;
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.SocketTimeoutException;
import java.net.URL;
import java.net.URLEncoder;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.springframework.web.multipart.MultipartFile;


public class HttpPostUtil {  
    URL url;  
    HttpURLConnection conn;  
    String boundary = "--------";  
    Map<String, String> textParams = new HashMap<String, String>();  
    List<MultipartFile> fileparams = new ArrayList<MultipartFile>();  
    List<File> fileList = new ArrayList<File>();
    List<String> urlList = new ArrayList<String>();
    DataOutputStream ds;  

    public HttpPostUtil(String url) throws Exception {  
        this.url = new URL(url);  
    }  
    //重新设置要请求的服务器地址，即上传文件的地址。  
    public void setUrl(String url) throws Exception {  
        this.url = new URL(url);  
    }  
    //增加一个普通字符串数据到form表单数据中  
    public void addTextParameter(String name, String value) {  
        textParams.put(name, value);  
    }  
    //增加一个文件到form表单数据中  
    public void addFileParameter(MultipartFile value) {  
        fileparams.add(value);  
    }
    //增加一个file类型的文件到form表单中
    public void addFileList(File value){
        fileList.add(value);
    }
    public void addUrlList(String str){
        urlList.add(str);
    }
    // 清空所有已添加的form表单数据  
    public void clearAllParameters() {  
        textParams.clear();  
        fileparams.clear();  
    }  
    // 发送数据到服务器，返回一个字节包含服务器的返回结果的数组  
    public String send() throws Exception {
        StringBuffer result = new StringBuffer();
        initConnection();  
        try {  
            conn.connect();  
        } catch (SocketTimeoutException e) {  
            // something  
            throw new RuntimeException();  
        }  
        ds = new DataOutputStream(conn.getOutputStream());  
        writeFileParams();  
        writeStringParams(); 
        writeFileList();
        writeUrlList();
        paramsEnd();  
        BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream(),
        "utf-8"));
        String line = "";
        while ((line = in.readLine()) != null) {
            result.append(line).append("
");
        }
        conn.disconnect();  
        return result.toString();  
    }  
    //文件上传的connection的一些必须设置  
    private void initConnection() throws Exception {  
        conn = (HttpURLConnection) this.url.openConnection();  
        conn.setDoOutput(true);  
        conn.setUseCaches(false);  
        conn.setConnectTimeout(10000); //连接超时为10秒  
        conn.setRequestMethod("POST"); 
        conn.setRequestProperty("Charsert", "UTF-8"); 
        conn.setRequestProperty("Accept-Charset", "utf-8");  
        conn.setRequestProperty("contentType", "utf-8");  
        conn.setRequestProperty("Content-Type", "text/plain; charset=utf-8");
        conn.setRequestProperty("Content-Type",  
                "multipart/form-data; boundary=" + boundary);  
    }  
    //普通字符串数据  
    private void writeStringParams() throws Exception {  
        Set<String> keySet = textParams.keySet();  
        for (Iterator<String> it = keySet.iterator(); it.hasNext();) {  
            String name = it.next();  
            String value = textParams.get(name);  
            ds.writeBytes("--" + boundary + "
");  
            ds.writeBytes("Content-Disposition: form-data; name="" + name + ""
");  
            ds.writeBytes("
");  
            ds.writeBytes(encode(value) + "
");   
        }
    }  
    //文件数据  
    private void writeFileParams() throws Exception {
        String name = "upload";
        for (MultipartFile file : fileparams) {  
            MultipartFile value = file;  
            ds.writeBytes("--" + boundary + "
");  
            ds.writeBytes("Content-Disposition: form-data; name="" + name  
                    + ""; filename="" + encode(value.getOriginalFilename()) + ""
");  
            ds.writeBytes("Content-Type: " + getContentType(value) + "
");  
            ds.writeBytes("
");  
            ds.write(getBytes(value));  
            ds.writeBytes("
");  
        }  
    } 
  //文件数据 (file) 
    private void writeFileList() throws Exception {
        String name = "upload";
        for (File file : fileList) {  
            File value = file;  
            ds.writeBytes("--" + boundary + "
");  
            ds.writeBytes("Content-Disposition: form-data; name="" + name  
                    + ""; filename="" + encode(value.getName()) + ""
");  
            ds.writeBytes("Content-Type:  image 
");  
            ds.writeBytes("
");  
            ds.write(getBytes(value));  
            ds.writeBytes("
");  
        }  
    }
  //文件数据 (url) 
    private void writeUrlList() throws Exception {
        String name = "upload";
        for (String strUrl : urlList) {  
            URL url = new URL(strUrl); 
            HttpURLConnection conn = (HttpURLConnection) url.openConnection(); 
            DataInputStream input = new DataInputStream(conn.getInputStream()); 
            DataOutputStream output = new DataOutputStream(new FileOutputStream(strUrl.substring(strUrl.lastIndexOf("/") + 1).toUpperCase())); 
            byte[] buffer = new byte[1024 * 8 * 1000]; 
            int count = 0; 
            count = input.read(buffer);
//            while ((count = input.read(buffer)) > 0) { 
//              output.write(buffer, 0, count); 
//            } 


            ds.writeBytes("--" + boundary + "
");  
            ds.writeBytes("Content-Disposition: form-data; name="" + name  
                    + ""; filename="" + encode(strUrl) + ""
");  
            ds.writeBytes("Content-Type:  image 
");  
            ds.writeBytes("
");  
            ds.write(buffer);  
            ds.writeBytes("
"); 
            output.close(); 
            input.close();
        }  
    }
    //获取文件的上传类型，图片格式为image/png,image/jpg等。非图片为application/octet-stream  
    private String getContentType(MultipartFile f) throws Exception {  

//      return "application/octet-stream";  // 此行不再细分是否为图片，全部作为application/octet-stream 类型  
//        ImageInputStream imagein = ImageIO.createImageInputStream(f);  
//        if (imagein == null) {  
//            return "application/octet-stream";  
//        }  
//        Iterator<ImageReader> it = ImageIO.getImageReaders(imagein);  
//        if (!it.hasNext()) {  
//            imagein.close();  
//            return "application/octet-stream";  
//        }  
//        imagein.close();  
//        return "image/" + it.next().getFormatName().toLowerCase();//将FormatName返回的值转换成小写，默认为大写  
        return "image";

    }  
    //把文件转换成字节数组  
    private byte[] getBytes(MultipartFile f) throws Exception { 
        InputStream is = f.getInputStream();
//        FileInputStream in = (FileInputStream)f.getInputStream();  修改，因图片太小，上传报错，直接使用inputstream即可。
        ByteArrayOutputStream out = new ByteArrayOutputStream();  
        byte[] b = new byte[1024];  
        int n;  
        while ((n = is.read(b)) != -1) {  
            out.write(b, 0, n);  
        }  
        is.close(); 
//        in.close();
        return out.toByteArray();  
    } 
  //把文件转换成字节数组  
    private byte[] getBytes(File f) throws Exception {  
        FileInputStream in = new FileInputStream(f);  
        ByteArrayOutputStream out = new ByteArrayOutputStream();  
        byte[] b = new byte[1024];  
        int n;  
        while ((n = in.read(b)) != -1) {  
            out.write(b, 0, n);  
        }  
        in.close();  
        return out.toByteArray();  
    } 
    //添加结尾数据  
    private void paramsEnd() throws Exception {  
        ds.writeBytes("--" + boundary + "--" + "
"); 
        ds.writeBytes("
");  
    }  
    // 对包含中文的字符串进行转码，此为UTF-8。服务器那边要进行一次解码  
    private String encode(String value) throws Exception{  
        return URLEncoder.encode(value, "UTF-8");  
    } 
    public static void main(String[] args) throws Exception {
        String postData = "{"id":"212","title":"测试1","content":"测试1","author":"测试1","createtime":"2016-3-4 15:25:16"}";
        String postUrl="http://localhost:81/qmcg/admin/interData/webSiteCase/outSideDataImp";
        HttpPostUtil u = new HttpPostUtil(postUrl);  
//        u.addFileParameter(new MultipartFile("d:/pvm.jpg"));
//        u.addFileParameter(new MultipartFile("d:/cb6c15f6-a187-3026-8911-03eec0a95cc2.png"));  
//        u.addTextParameter("gson", postData);   
        u.addUrlList("http://127.0.0.1:81/pirImg/upload/Image/201608/20160826152343638.png");
        String result = u.send();   

        System.out.println("result:"+result);  
    }   

}  

开始时，上传图片正常，后来无意间发现有一些图片上传失败，报的错误为ByteArrayInputStream不能转化成FileInputStream，
后来发现，是因为图片太小的事，大图片没有问题，经过修改后是这样

图片中红框内注释的为以前的代码。