多线程下载 断点续传

package wml.dl;
import java.io.BufferedInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.util.Properties;
import wml.dl.io.BufferedRandomOutputStream;
* 下载线程，负责下载DLBlock
* @author wml
public class DLThread implements Runnable {
private static final int INPUT_BUFFER_SIZE = 1024;
private static final int OUTPUT_BUFFER_SIZE = 8192;
private DLTask task;
private DLBlock block;
private boolean isDone;
private boolean isStop;
public DLBlock getBlock() {
return block;
public DLThread(DLTask task, DLBlock block) {
this.task = task;
this.block = block;
@Override
public void run() {
block.setStatus(DLBlock.STATUS_RUNNING);
BufferedRandomOutputStream randomOutputStream = null;
try {
randomOutputStream = new BufferedRandomOutputStream(task.openRandomAccessFile(), OUTPUT_BUFFER_SIZE);
} catch (FileNotFoundException e) {
block.setThrowable(e);
e.printStackTrace();
isDone = true;
return;
HttpURLConnection conn = null;
long downloadPosition = 0;
try { http://www.huiyi8.com/gundongdaima/ 滚动代码
if(task.isSupportedContentRange()) {//断点续传
block.setDownloaded(Math.max(block.getDownloaded() - OUTPUT_BUFFER_SIZE, 0));// -8kb保证下载结果(有可能之前写入失败)
downloadPosition = block.getBegin() + block.getDownloaded();
randomOutputStream.seek(downloadPosition);
Properties reqProps = new Properties();
if(task.isSupportedContentRange()) {//设置下载范围
reqProps.setProperty("Range", "bytes=" + downloadPosition + "-" + block.getEnd());
conn = DLUtils.getChromeURLConnection(task.getUri(), false, reqProps);
InputStream in = new BufferedInputStream(DLUtils.getInputStream(conn.getInputStream(), conn.getContentEncoding()), INPUT_BUFFER_SIZE);
byte[] buf = new byte[INPUT_BUFFER_SIZE];
int len;
while((len = in.read(buf)) != -1) {
randomOutputStream.write(buf, 0, len);
block.updateDownloaded(len);

downloadPosition += len;

if(task.isSupportedContentRange() && downloadPosition >= block.getEnd()
|| isStop
|| !task.isRunning()) {
//也许将任务部分分配给了其他线程（增加了线程），在后面做详细处理
break;
} catch (IOException e) {

block.setThrowable(e);
e.printStackTrace();

} finally {

DLUtils.close(conn);
DLUtils.close(randomOutputStream);

isDone = true;

if(downloadPosition >= block.getEnd()) {

//块下载完成
block.setStatus(DLBlock.STATUS_DONE);

} else {

//停止下载
block.setStatus(DLBlock.STATUS_PAUSE);
try {//检查并设置任务状态
task.checkDone();
} catch (FileNotFoundException e) {

block.setThrowable(e);
e.printStackTrace();
public boolean isDone() {
return isDone;
}

public void stop() {
isStop = true;
}