Java HttpURLConnection | HttpsURLConnection > Implement Pause / Resume in File Downloading > How to Extract Chunked Data When Using HttpURLConnection > Download File as Chunk

It's very important (as well as beneficial) if we can pause / resume our download specially when downloading big file.

Below is a code snippet to download data chunk by chunk. So you can now pause / resume your download whenever you want.

package com.pkm; import java.io.*; import java.net.HttpURLConnection; import java.net.URL; import java.util.List; import java.util.Map; public class JavaChunkDataDownload { public static enum Method { GET, POST, PUT, PATCH, DELETE } public static enum Type { XML, JSON, URL_ENCODED; }; private static String fileName = "file2.zip"; public static void main(String[] args) throws Exception { String URI = "http://ipv4.download.thinkbroadband.com/100MB.zip?t=" + System.currentTimeMillis(); //URI = "http://localhost/ForDownload.zip?t=" + System.currentTimeMillis(); Response response = execute(URI, Method.GET, "", Type.URL_ENCODED); println("Get_Result:\n" + lengthString(response.toString().replace("\n", ""), 400) + "..."); } public static Response execute(String url, Method method, String data, Type type) { return execute(url, method, data, type, null, null); } private static Response execute(String requestURL, Method requestMethod, String requestData, Type dataType, Map headers, Integer timeOutMilli) { Long started = System.currentTimeMillis(); String httpResponse = "", responseMessage = ""; Integer httpCode = 0; timeOutMilli = timeOutMilli == null ? 1000 * 30 : timeOutMilli; /* Default read & write timeout */ HttpURLConnection connection = null; try { String contentType = "", accept = "", contentLength = "" + requestData.length(); switch (dataType) { case XML: contentType = "text/xml; charset=utf-8"; accept = "text/xml"; break; case JSON: contentType = "application/json"; break; case URL_ENCODED: contentType = "application/x-www-form-urlencoded"; break; } connection = (HttpURLConnection) new URL(requestURL).openConnection(); connection.setRequestMethod(requestMethod.name()); connection.setConnectTimeout(timeOutMilli); connection.setReadTimeout(timeOutMilli); connection.setRequestProperty("Pragma", "no-cache"); connection.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36"); File outputFileCache = new File(fileName); if (outputFileCache.exists()) { connection.setAllowUserInteraction(true); connection.setRequestProperty("Range", "bytes=" + outputFileCache.length() + "-"); } if (headers != null && headers.size() > 0) { for (Object name : headers.keySet().toArray()) { connection.setRequestProperty(name.toString(), headers.get(name.toString()).toString()); } } if (requestData.length() > 0) { connection.setDoInput(true); connection.setDoOutput(true); if (accept.length() > 0) { connection.setRequestProperty("Accept", accept); } if (contentType.length() > 0) { connection.setRequestProperty("Content-Type", contentType); } connection.setRequestProperty("Content_length", contentLength); OutputStreamWriter writer = new OutputStreamWriter(connection.getOutputStream(), "UTF-8"); writer.write(requestData); writer.flush(); writer.close(); } httpCode = connection.getResponseCode(); Boolean validResponse = httpCode >= 200 && httpCode <= 299; responseMessage = connection.getResponseMessage(); String responseContentType = connection.getContentType(); if (responseContentType == null || responseContentType.length() == 0) { responseContentType = "txt"; } else { if (responseContentType.contains(";")) { responseContentType = responseContentType.substring(0, responseContentType.indexOf(";")); } if (responseContentType.contains("text/html")) { responseContentType = "html"; } else if (responseContentType.contains("image/")) { responseContentType = "image"; } else if (responseContentType.contains("/")) { String[] parts = responseContentType.split("/"); responseContentType = parts[parts.length - 1]; } } Map<String, List<String>> map = connection.getHeaderFields(); for (Map.Entry<String, List<String>> entry : map.entrySet()) { System.out.println("Key : " + entry.getKey() + " ,Value : " + entry.getValue()); } if (validResponse) { Long downloadedSize = 0L; String connectionField = connection.getHeaderField("content-range"); if (connectionField != null) { String[] connectionRanges = connectionField.substring("bytes=".length()).split("-"); downloadedSize = Long.valueOf(connectionRanges[0]); } if (connectionField == null && outputFileCache.exists()) { outputFileCache.delete(); } outputFileCache = new File(fileName); if (!outputFileCache.exists()) { outputFileCache.createNewFile(); outputFileCache.setExecutable(true); } Long fileLength = connection.getContentLength() + downloadedSize; RandomAccessFile output = new RandomAccessFile(outputFileCache, "rw"); output.seek(downloadedSize); InputStream is = connection.getInputStream(); BufferedInputStream input = new BufferedInputStream(is); int readSize = 1024; byte data[] = new byte[readSize]; int count = 0; int progress = 0; Integer pauseAt = 180; Long timeNeeded = System.currentTimeMillis(); while ((count = input.read(data, 0, readSize)) >= 0 && progress != 100) { downloadedSize += count; output.write(data, 0, count); progress = (int) ((downloadedSize * 100) / fileLength); Long mb = output.length() / (1024 * 1024); System.out.println("PROGRESS = " + (progress) + "%, DOWNLOADED=" + mb + " MB, TYPE=" + responseContentType); if (progress >= pauseAt) { break; } } output.close(); input.close(); timeNeeded = (System.currentTimeMillis() - timeNeeded) / 1000; System.out.println("TIME REQUIRED=" + timeNeeded); } } catch (Exception ex) { httpResponse = ""; responseMessage = ex.getMessage(); } finally { try { connection.disconnect(); } catch (Exception ex10) { } } return new Response(requestURL, httpCode, responseMessage, httpResponse, (System.currentTimeMillis() - started)); } public static class Response { private String url; private Integer code; private String message; private String body; private Long time; public Response(String url, Integer code, String message, String body, Long time) { this.url = url; this.code = code; this.message = message; this.body = body; this.time = time; } @Override public String toString() { return "{URL=" + this.url + ",Code=" + this.code + ", Message=" + this.message + ", Time=" + this.time + " Millis, Body=" + this.body + "}"; } public Integer getCode() { return this.code; } public String getMessage() { return this.message; } public String getBody() { return this.body; } public Long getTime() { return this.time; } } public static void println(Object o) { System.out.println("" + o); } public static String lengthString(String s, Integer m) { return s.length() > m ? s.substring(0, m) : s; } }