HTTP多线程断点续传下载的尝试[Java编程]
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直接看代码吧,废话一点不多说.
功效介绍:
1 多线程HTTP下载
2 支持断点续传
3 暂时文件下载,成功后改名
4 供应防盗链的破解
Java代码
package net.java2000.tools;
import java.io.BufferedInputStream;
import java.io.BufferedWriter;
import java.io.File;
import java.io.OutputStreamWriter;
import java.io.RandomAccessFile;
import java.net.Socket;
import java.net.URL;
import java.net.URLConnection;
import java.util.HashMap;
import java.util.Map;
/**
* HTTP的多线程下载工具.
*
* @author 赵学庆 www.java2000.net
*/
public class HTTPDownloader extends Thread {
// 要下载的页面
private String page;
// 保存的途径
private String savePath;
// 线程数
private int threadNumber = 2;
// 根源地址
private String referer;
private String cookie;
int threadPointer = 0;
private Map<Integer, HTTPDownloaderThread> threadPool = new HashMap<Integer, HTTPDownloaderThread>(); // 线程迟
// 最小的块尺寸.假如文件尺寸除以线程数小于这个,则会削减线程数.
private int MIN_BLOCK = 10 * 1024;
public static void main(String[] args) throws Exception {
HTTPDownloader d = new HTTPDownloader ("http://www.xxxxx.com/a.rar", null, "d://a.rar", 10, null);
d.down();
}
public void run() {
try {
down();
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 下载操作
*
* @throws Exception
*/
public void down() throws Exception {
URL url = new URL(page); // 成立URL
URLConnection con = url.openConnection(); // 成立衔接
con.setRequestProperty("Referer", referer == null ? page : referer);
con.setRequestProperty("UserAgent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; flashget)");
int contentLen = con.getContentLength(); // 得到资源长度
if ((contentLen / MIN_BLOCK + 1) < threadNumber) {
threadNumber = contentLen / MIN_BLOCK + 1; // 调整 下载线程数
}
if (threadNumber > 10) {
threadNumber = 10;
}
int begin = 0;
int step = contentLen / threadNumber + 1;
int end = 0;
HTTPDownloaderThread thread;
for (threadPointer = 0; threadPointer < threadNumber; threadPointer++) {
end += step;
if (end > contentLen) {
end = contentLen;
}
thread = new HTTPDownloaderThread(this, threadPointer, begin, end);
threadPool.put(threadPointer, thread);
thread.start();
begin = end;
}
}
/**
* 一个线程完活了.
*
* @param id 完活的线程id
*/
public synchronized void finished(int id) {
threadNumber--;
threadPool.remove(id);
if (threadNumber <= 0) {
System.out.println("FINISHED:" + savePath);
File f1 = new File(savePath + ".tmp");
File f2 = new File(savePath);
// 假如目标文件已经存在,则尝试删除它
// 最多尝试3次,隔断1秒钟.
int times = 3;
while (f2.exists() && times > 0) {
if (f2.delete()) {
break;
}
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
times--;
}
if (!f2.exists()) {
if (!f1.renameTo(f2)) {
System.out.println("改名失利!");
}
} else {
System.out.println("目标文件存在,且无法删除,无法 改名");
}
} else {
int size = 0;
HTTPDownloaderThread o = null;
// 尝试查找一个可以分担的线程
for (HTTPDownloaderThread thread : threadPool.values ()) {
if (thread.endPos - thread.curPos > size) {
size = thread.endPos - thread.curPos;
o = thread;
}
}
if (size > MIN_BLOCK * 2) {
if (o.isAlive()) {
int endPos = o.endPos;
int beginPos = o.endPos - ((o.endPos - o.curPos) / 2);
o.endPos = beginPos;
threadNumber++;
threadPointer++;
HTTPDownloaderThread thread = new HTTPDownloaderThread(this, threadPointer, beginPos, endPos);
threadPool.put(threadPointer, thread);
System.out.println("A Help Thread for " + o.id + " is started with:" + threadPointer);
thread.start();
}
}
}
}
public HTTPDownloader() {
}
/**
* 下载
*
* @param page 被下载的页面
* @param savePath 保存的途径
*/
public HTTPDownloader(String page, String savePath) {
this(page, savePath, 10);
}
/**
* 下载
*
* @param page 被下载的页面
* @param savePath 保存的途径
* @param threadNumber 线程数
*/
public HTTPDownloader(String page, String savePath, int threadNumber) {
this(page, page, savePath, 10, null);
}
/**
* 下载
*
* @param page 被下载的页面
* @param savePath 保存的途径
* @param threadNumber 线程数
* @param referer 根源
*/
public HTTPDownloader(String page, String referer, String savePath, int threadNumber, String cookie) {
this.page = page;
this.savePath = savePath;
this.threadNumber = threadNumber;
this.referer = referer;
}
public String getPage() {
return page;
}
public void setPage(String page) {
this.page = page;
}
public String getSavePath() {
return savePath;
}
public void setSavePath(String savePath) {
this.savePath = savePath;
}
public int getThreadNumber() {
return threadNumber;
}
public void setThreadNumber(int threadNumber) {
this.threadNumber = threadNumber;
}
public String getReferer() {
return referer;
}
public void setReferer(String referer) {
this.referer = referer;
}
public String getCookie() {
return cookie;
}
public void setCookie(String cookie) {
this.cookie = cookie;
}
}
/**
* 下载线程
*
* @author 赵学庆 www.java2000.net
*/
class HTTPDownloaderThread extends Thread {
HTTPDownloader manager;
int startPos;
int endPos;
int id;
int curPos;
int BUFFER_SIZE = 40960;
int readByte = 0;
HTTPDownloaderThread(HTTPDownloader manager, int id, int startPos, int endPos) {
this.id = id;
this.manager = manager;
this.startPos = startPos;
this.endPos = endPos;
}
public void run() {
System.out.println("线程" + id + "启 动," + startPos + "-" + endPos);
// 成立一个buff
BufferedInputStream bis = null;
RandomAccessFile fos = null;
// 缓冲区大小
byte[] buf = new byte[BUFFER_SIZE];
boolean timeout = false;
Socket socket = null;
try {
curPos = startPos;
File file = new File(manager.getSavePath() + ".tmp");
// 成立RandomAccessFile
fos = new RandomAccessFile(file, "rw");
// 从startPos开始
fos.seek(startPos);
int index = manager.getPage().indexOf("/", 8);
String host = manager.getPage().substring(7, index);
// System.out.println(host);
socket = new Socket(host, 80);
socket.setSoTimeout(30000);
// 写入数据
BufferedWriter wr = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream(), "UTF-8"));
StringBuilder b = new StringBuilder();
b.append("GET " + manager.getPage ().substring(index) + " HTTP/1.1rn");
b.append("Host: " + host + "rn");
b.append("Referer: " + (manager.getReferer() == null ? manager.getPage() : manager.getReferer()) + "rn");
b.append("UserAgent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; flashget; rn");
b.append("Range: bytes=" + startPos + "-" + endPos + "rn");
b.append("rn");
// System.out.println(b.toString());
wr.write(b.toString());
wr.flush();
// 下面一段向按照文件写入数据,curPos为当前写入的未知,这里 会判断能否小于endPos,
// 假如超越endPos就代表该线程已经履行完毕
bis = new BufferedInputStream(socket.getInputStream ());
// 读取直到换行
int ch;
boolean foundBR = false;
while (true) {
ch = bis.read();
if (ch == 0xD) {
ch = bis.read();
if (ch == 0xA) {
if (foundBR) {
break;
}
foundBR = true;
} else {
foundBR = false;
}
} else {
foundBR = false;
}
}
int len = -1;
while (curPos < endPos) {
// System.out.println(id + "=" + (endPos - curPos));
len = bis.read(buf, 0, BUFFER_SIZE);
if (len == -1) {
break;
}
fos.write(buf, 0, len);
// System.out.println(id + "=Write OK! ");
curPos = curPos + len;
if (curPos > endPos) {
// 获得精确读取的字节数
readByte += len - (curPos - endPos) + 1;
} else {
readByte += len;
}
}
System.out.println("线程" + id + "已经 下载完毕:" + readByte);
} catch (Exception ex) {
timeout = true;
} finally {
if (bis != null) {
try {
bis.close();
} catch (Exception e) {
System.out.println("关闭文件失利(1)! ");
}
}
if (fos != null) {
try {
fos.close();
} catch (Exception e) {
System.out.println("关闭文件失利(2)! ");
}
}
if (socket != null) {
try {
socket.close();
} catch (Exception e) {
System.out.println("关闭链接失利!");
}
}
}
if (timeout) {
System.out.println(id + " timeout, restart...");
new HTTPDownloaderThread(manager, id, curPos, endPos).start();
} else {
manager.finished(id);
}
}
}
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