在java中恢复http文件下载

问题描述

URL url = new URL("http://download.thinkbroadband.com/20MB.zip");

URLConnection connection = url.openConnection();
File fileThatExists = new File(path);
OutputStream output = new FileOutputStream(path, true);
connection.setRequestProperty("Range", "bytes=" + fileThatExists.length() + "-");

connection.connect();

int lenghtOfFile = connection.getContentLength();

InputStream input = new BufferedInputStream(url.openStream());
byte data[] = new byte[1024];

long total = 0;

while ((count = input.read(data)) != -1) {
    total += count;

    output.write(data, 0 , count);
}

在这段代码中，我尝试恢复下载.目标文件为 20MB.但是当我停止下载 10MB 时，然后继续，我得到文件大小为 30MB 的文件.它似乎继续写入文件，但无法从服务器部分下载.Wget -c 可以很好地处理这个文件.如何恢复文件下载?

in this code I try to resume download. Target file is 20MB. But when I stop download on 10mb, then contunue, I get file with filesize 30MB. It seems that it continue writing to file, but cant partly download from server. Wget -c works great with this file. How can I resume file download?

推荐答案

 HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    if(ISSUE_DOWNLOAD_STATUS.intValue()==ECMConstant.ECM_DOWNLOADING){
        File file=new File(DESTINATION_PATH);
        if(file.exists()){
             downloaded = (int) file.length();
             connection.setRequestProperty("Range", "bytes="+(file.length())+"-");
        }
    }else{
        connection.setRequestProperty("Range", "bytes=" + downloaded + "-");
    }
    connection.setDoInput(true);
    connection.setDoOutput(true);
    progressBar.setMax(connection.getContentLength());
     in = new BufferedInputStream(connection.getInputStream());
     fos=(downloaded==0)? new FileOutputStream(DESTINATION_PATH): new FileOutputStream(DESTINATION_PATH,true);
     bout = new BufferedOutputStream(fos, 1024);
    byte[] data = new byte[1024];
    int x = 0;
    while ((x = in.read(data, 0, 1024)) >= 0) {
        bout.write(data, 0, x);
         downloaded += x;
         progressBar.setProgress(downloaded);
    }

这不是我的代码，但它有效.

This is not my code, but it works.

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