Java实现断点下载服务端与客户端的示例代码

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 

/** * 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; }> 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(); } } 

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

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); } }

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"); } });