Java 断点下载(下载续传)服务端及客户端（Android）代码 - ToB企服应用市场:ToB评测及商务社交产业平台

Range:bytes=300-800
//客户端需要文件300-800字节范围的数据（即500B数据）
Range:bytes=300-
//客户端需要文件300字节之后的数据

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/**
* 断点下载文件
*
* @return
*/
@GetMapping("download")
public void download( HttpServletRequest request, HttpServletResponse response) throws IOException {
//todo 这里文件按照你的需求调整
File file = new File("D:\\temp\\测试文件.zip");
if (!file.exists()) {
response.setStatus(HttpStatus.NOT_FOUND.value());
return;
}
long fromPos = 0;
long downloadSize = file.length();
if (request.getHeader("Range") != null) {
response.setStatus(HttpServletResponse.SC_PARTIAL_CONTENT);
String[] ary = request.getHeader("Range").replaceAll("bytes=", "").split("-");
fromPos = Long.parseLong(ary[0]);
downloadSize = (ary.length < 2 ? downloadSize : Long.parseLong(ary[1])) - fromPos;
}
//注意下面设置的相关请求头
response.setContentType(MediaType.APPLICATION_OCTET_STREAM_VALUE);
//相当于设置请求头content-length
response.setContentLengthLong(downloadSize);
//使用URLEncoder处理中文名(否则会出现乱码)
response.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(file.getName(), "UTF-8"));
response.setHeader("Accept-Ranges", "bytes");
response.setHeader("Content-Range", String.format("bytes %s-%s/%s", fromPos, (fromPos + downloadSize), downloadSize));
RandomAccessFile randomAccessFile = new RandomAccessFile(file, "rw");
randomAccessFile.seek(fromPos);
FileChannel inChannel = randomAccessFile.getChannel();
WritableByteChannel outChannel = Channels.newChannel(response.getOutputStream());
try {
while (downloadSize > 0) {
long count = inChannel.transferTo(fromPos, downloadSize, outChannel);
if (count > 0) {
fromPos += count;
downloadSize -= count;
}
}
inChannel.close();
outChannel.close();
randomAccessFile.close();
} catch (IOException e) {
e.printStackTrace();
}
}

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implementation 'com.squareup.okhttp3:okhttp:3.9.0'

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package com.tyky.update.utils;
import com.blankj.utilcode.util.ThreadUtils;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.math.BigDecimal;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.FileChannel;
import java.nio.channels.ReadableByteChannel;
import okhttp3.Call;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
public class FileDownloadUtil {
public static void download(String url, File file, OnDownloadListener listener) {
//http://10.232.107.44:9060/swan-business/file/download
// 利用通道完成文件的复制(非直接缓冲区)
ThreadUtils.getIoPool().submit(new Runnable() {
@Override
public void run() {
try {
//续传开始的进度
long startSize = 0;
if (file.exists()) {
startSize = file.length();
}
OkHttpClient okHttpClient = new OkHttpClient.Builder().build();
Request request = new Request.Builder().url(url)
.addHeader("Range", "bytes=" + startSize)
.get().build();
Call call = okHttpClient.newCall(request);
Response resp = call.execute();
double length = Long.parseLong(resp.header("Content-Length")) * 1.0;
InputStream fis = resp.body().byteStream();
ReadableByteChannel fisChannel = Channels.newChannel(fis);
RandomAccessFile randomAccessFile = new RandomAccessFile(file, "rw");
//从上次未完成的位置开始下载
randomAccessFile.seek(startSize);
FileChannel foschannel = randomAccessFile.getChannel();
// 通道没有办法传输数据，必须依赖缓冲区
// 分配指定大小的缓冲区
ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
// 将通道中的数据存入缓冲区中
while (fisChannel.read(byteBuffer) != -1) { // fisChannel 中的数据读到 byteBuffer 缓冲区中
byteBuffer.flip(); // 切换成读数据模式
// 将缓冲区中的数据写入通道
foschannel.write(byteBuffer);
final double progress = (foschannel.size() / length);
BigDecimal two = new BigDecimal(progress);
double result = two.setScale(2,BigDecimal.ROUND_HALF_UP).doubleValue();
//计算进度，回调
if (listener != null) {
listener.onProgress(result);
}
byteBuffer.clear(); // 清空缓冲区
}
foschannel.close();
fisChannel.close();
randomAccessFile.close();
if (listener != null) {
listener.onSuccess(file);
}
} catch (IOException e) {
if (listener != null) {
listener.onError(e);
}
}
}
});
}
public interface OnDownloadListener {
void onProgress(double progress);
void onError(Exception e);
void onSuccess(File outputFile);
}
}

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FileDownloadUtil.download(downloadUrl, file, new FileDownloadUtil.OnDownloadListener() {
@Override
public void onProgress(double progress) {
KLog.d("下载进度: " + progress);
}
@Override
public void onError(Exception e) {
KLog.e("下载错误: " + e.getMessage());
}
@Override
public void onSuccess(File outputFile) {
KLog.d("下载成功");
}
});

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