java多线程    Java入门    vsftp    ftp    linux配置    centos    FRP教程    HBase    Html5缓存    webp    zabbix    分布式    neo4j图数据库    

慢慢读，java断点续传多线程下载

发表于 2012-12-24 03:16:09 by 月小升

java下载断点续传简单而言就是记录上次下载的位置，下次直接跳到这个位置开始下载就好了。

断点继续下载算法

package com.javaer.examples.file;


import java.io.DataOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.math.BigDecimal;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.util.UUID;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * 
 * @author why
 *
 */
public class MutiGoOn {
	//文件目录、文件名
	public String fileDir = "E:/MyDownLoad";
	public String fileName;
	//超时重连时间
	public long reconnectTime = 5;
	//线程数
	private int poolSize = 5;
	//每个线程的缓冲区大小
	public int bufferSize = 1024;
	//url地址
	private String urlLocation = null;
	
	public MutiGoOn(){}
	public MutiGoOn(String url){
		this.urlLocation = url;
	}
	public void downLoad(){
		if(this.urlLocation == null || "".equals(this.urlLocation))return;
		downLoad(this.urlLocation);
	}
	public void downLoad(String urlLocation){
		File file = null;
		File tempFile = null;
		CountDownLatch latch;
		URL url = null;
		ExecutorService pool = Executors.newCachedThreadPool();
		long contentLength = 0;
		long threadLength = 0;
		try {
			//如果未指定名称，则从url中获得下载的文件格式与名字
			if(fileName == null || "".equals(fileName)){
				this.fileName = urlLocation.substring(urlLocation.lastIndexOf("/") + 1,
						urlLocation.lastIndexOf("?") > 0 ? urlLocation.lastIndexOf("?")
								: urlLocation.length());
				if ("".equalsIgnoreCase(this.fileName)) {
					this.fileName = UUID.randomUUID().toString();
				}
			}
			new File(fileDir).mkdirs();
			file = new File(fileDir + File.separator + fileName);
			tempFile = new File(fileDir + File.separator + fileName + "_temp");
			
			url = new URL(urlLocation);
			HttpURLConnection conn = (HttpURLConnection) url.openConnection();
			setHeader(conn);
			//得到content的长度
			contentLength = conn.getContentLength();
			
			System.out.println("total length=" + contentLength);
			
			//把context分为poolSize段，计算每段的长度。
//			threadLength = contentLength / this.poolSize;
			BigDecimal b1 = new BigDecimal(Double.toString(contentLength));
			BigDecimal b2 = new BigDecimal(Double.toString(this.poolSize));
			threadLength = b1.divide(b2, 0, BigDecimal.ROUND_HALF_UP).longValue();
			
			if(file.exists() && tempFile.exists()){
				//如果文件已存在，根据临时文件中记载的线程数量，继续上次的任务
				latch = new CountDownLatch((int)tempFile.length()/28);
				for(int i=0;i

下载算法


package com.javaer.examples.file;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.util.concurrent.Callable;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;

/**
 * 
 * @author why
 *
 */
public class MutiGoOnTask implements Callable{
	//超时重连时间
	private long reconnectTime = 5;
	//缓冲区大小
	private int bufferSize = 1024;
	
	private CountDownLatch latch;
	private RandomAccessFile file = null;
	private RandomAccessFile tempFile = null;
	private URL url = null;
	private int id;
	private long startPosition;
	private long endPosition;
	private long currentPosition ;
	
	public MutiGoOnTask(File file,File tempFile,URL url,int id,CountDownLatch latch,long reconnectTime,int bufferSize){
		try {
			this.file = new RandomAccessFile(file, "rw");
			this.tempFile = new RandomAccessFile(tempFile, "rw");
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		}
		this.url = url;
		this.id = id;
		this.latch = latch;
	}
	
	public String call(){
		
		try {
			tempFile.seek((id-1)*28);
			tempFile.readInt();
			this.startPosition = tempFile.readLong();
			this.endPosition = tempFile.readLong();
			this.currentPosition = tempFile.readLong();
		} catch (IOException e) {
			e.printStackTrace();
		}
		
		System.out.println("Thread " + id + " begin!");
		
		HttpURLConnection conn = null;
		InputStream inputStream = null;

		while(true){
			try {
				tempFile.seek(id*28 - 8);
				// 打开URLConnection
				conn = (HttpURLConnection) this.url.openConnection();
				setHeader(conn);
				// 设置连接超时时间为10000ms
				conn.setConnectTimeout(10000);
				// 设置读取数据超时时间为10000ms
				conn.setReadTimeout(10000);

				if (currentPosition < endPosition) {
					// 设置下载数据的起止区间
					conn.setRequestProperty("Range", "bytes=" + currentPosition + "-" + endPosition);
					
					System.out.println("Thread " + id + " startPosition=" + startPosition 
							+ ",endPosition=" + endPosition + ",currentPosition=" + currentPosition);

					file.seek(currentPosition);

					// 判断http status是否为HTTP/1.1 206 Partial Content或者200 OK
					// 如果不是以上两种状态，把status改为STATUS_HTTPSTATUS_ERROR
					if (conn.getResponseCode() != HttpURLConnection.HTTP_OK
							&& conn.getResponseCode() != HttpURLConnection.HTTP_PARTIAL) {
						System.out.println("Thread " + id + ": code = " + conn.getResponseCode() + ", status = " + conn.getResponseMessage());
						file.close();
						conn.disconnect();
						System.out.println("Thread " + id + " finished.");
						break;
					}

					inputStream = conn.getInputStream();
					int len = 0;
					byte[] b = new byte[bufferSize];
					while ((len = inputStream.read(b)) != -1) {
						file.write(b, 0, len);

						currentPosition += len;
						// set tempFile now position
						tempFile.seek(id*28 - 8);
						tempFile.writeLong(currentPosition);
					}

					file.close();
					tempFile.close();
					inputStream.close();
					conn.disconnect();
				}

				System.out.println("Thread " + id + " finished.");
				break;
			} catch (IOException e) {
				try {
					TimeUnit.SECONDS.sleep(getReconnectTime());
				} catch (InterruptedException e1) {
					e1.printStackTrace();
				}
				continue;
			}
		}
		latch.countDown();
		return "finish";
	}
	
	private void setHeader(URLConnection conn) {
		conn.setRequestProperty("User-Agent",
						"Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.0.3) Gecko/2008092510 Ubuntu/8.04 (hardy) Firefox/3.0.3");
		conn.setRequestProperty("Accept-Language", "en-us,en;q=0.7,zh-cn;q=0.3");
		conn.setRequestProperty("Accept-Encoding", "aa");
		conn.setRequestProperty("Accept-Charset","ISO-8859-1,utf-8;q=0.7,*;q=0.7");
		conn.setRequestProperty("Keep-Alive", "300");
		conn.setRequestProperty("Connection", "keep-alive");
		conn.setRequestProperty("If-Modified-Since", "Fri, 02 Jan 2009 17:00:05 GMT");
		conn.setRequestProperty("If-None-Match", "\"1261d8-4290-df64d224\"");
		conn.setRequestProperty("Cache-Control", "max-age=0");
		conn.setRequestProperty("Referer","http://www.skycn.com/soft/14857.html");
	}

	public long getReconnectTime() {
		return reconnectTime;
	}

	public void setReconnectTime(long reconnectTime) {
		this.reconnectTime = reconnectTime;
	}

	public int getBufferSize() {
		return bufferSize;
	}

	public void setBufferSize(int bufferSize) {
		this.bufferSize = bufferSize;
	}

	
}


















						This entry was posted in JAVA and tagged , , . Bookmark the permalink.											





月小升QQ 2651044202, 技术交流QQ群 178491360 



首发地址：月小升博客 – https://java-er.com/blog/java-d-dow/

 无特殊说明，文章均为月小升原创，欢迎转载，转载请注明本文地址，谢谢
您的评论是我写作的动力.

2 Responses to 慢慢读，java断点续传多线程下载

  1. 益**汤 says:
    2012 年 12 月 25 日 at am 12:24

    佩服，佩服，可以转载吗？

Leave a Reply

近期文章

  1. Centos安装mysql9
  2. certbot 申请Let’s Encrypt泛域名SSL证书
  3. php8 编译zip
  4. docker 快速操作笔记
  5. 软件概要设计和详细设计的区别
  6. Spring AOP理解
  7. Spring IOC的理解
  8. Java的双亲委派模型
  9. JVM中引用的分类
  10. 柔性事务是什么，分布式环境为何要放弃传统事务

标签

    Android Apache cookie frp FTP google HBase html5 iphone java java基础教程 java教程 jQuery linux Linux命令 mac mac软件 MongoDB mysql neo4j nginx nosql php php-fpm php函数 python redis shell SVN swift Ubuntu Windows wordpress wordpress插件 xcode zabbix 值得记忆 图片 多线程 密码 插件 数据库 日志 服务器 缓存

分类

  1. JAVA
  2. Linux
  3. MAC
  4. Perl
  5. PHP
  6. Python
  7. WEB前端
  8. Windows
  9. 互联网观察
  10. 吐槽
  11. 技术管理
  12. 数学与算法
  13. 数据库
  14. 日常随笔
  15. 月小升软件
  16. 电商运营
  17. 科技精品
  18. 程序视点
  19. 网络推广
  20. 运营
  21. 阅读笔记
  22. 高并发与大数据