用java实现断点续传(http)（2）

(三)断点续传内核的实现
主要用了6个类，包括一个测试类。
sitefilefetch.java负责整个文件的抓取，控制内部线程(filesplitterfetch类)。
filesplitterfetch.java负责部分文件的抓取。
fileaccess.java负责文件的存储。
siteinfobean.java要抓取的文件的信息，如文件保存的目录，名字，抓取文件的url等。
utility.java工具类，放一些简单的方法。
testmethod.java测试类。

下面是源程序：

/*
**sitefilefetch.java
*/
package netfox;
import java.io.*;
import java.net.*;


public class sitefilefetch extends thread {


siteinfobean siteinfobean = null; //文件信息bean
long[] nstartpos; //开始位置
long[] nendpos; //结束位置
filesplitterfetch[] filesplitterfetch; //子线程对象
long nfilelength; //文件长度
boolean bfirst = true; //是否第一次取文件
boolean bstop = false; //停止标志
file tmpfile; //文件下载的临时信息
dataoutputstream output; //输出到文件的输出流

public sitefilefetch(siteinfobean bean) throws ioexception
{
siteinfobean = bean;
//tmpfile = file.createtempfile ("zhong","1111",new file(bean.getsfilepath()));
tmpfile = new file(bean.getsfilepath()+file.separator + bean.getsfilename()+".info");
if(tmpfile.exists ())
{
bfirst = false;
read_npos();
}
else
{
nstartpos = new long[bean.getnsplitter()];
nendpos = new long[bean.getnsplitter()];
}

}

public void run()
{
//获得文件长度
//分割文件
//实例filesplitterfetch
//启动filesplitterfetch线程
//等待子线程返回
try{
if(bfirst)
{
nfilelength = getfilesize();
if(nfilelength == -1)
{
system.err.println("file length is not known!");
}
else if(nfilelength == -2)
{
system.err.println("file is not access!");
}
else
{
for(int i=0;i<nstartpos.length;i++)
{
nstartpos[i] = (long)(i*(nfilelength/nstartpos.length));
}
for(int i=0;i<nendpos.length-1;i++)
{
nendpos[i] = nstartpos[i+1];
}
nendpos[nendpos.length-1] = nfilelength;
}
}

//启动子线程
filesplitterfetch = new filesplitterfetch[nstartpos.length];
for(int i=0;i<nstartpos.length;i++)
{
filesplitterfetch[i] = new filesplitterfetch(siteinfobean.getssiteurl(),
siteinfobean.getsfilepath() + file.separator + siteinfobean.getsfilename(),
nstartpos[i],nendpos[i],i);
utility.log("thread " + i + " , nstartpos = " + nstartpos[i] + ", nendpos = " + nendpos[i]);
filesplitterfetch[i].start();
}
// filesplitterfetch[npos.length-1] = new filesplitterfetch(siteinfobean.getssiteurl(),
siteinfobean.getsfilepath() + file.separator + siteinfobean.getsfilename(),npos[npos.length-1],nfilelength,npos.length-1);
// utility.log("thread " + (npos.length-1) + " , nstartpos = " + npos[npos.length-1] + ",
nendpos = " + nfilelength);
// filesplitterfetch[npos.length-1].start();


//等待子线程结束
//int count = 0;
//是否结束while循环
boolean breakwhile = false;

while(!bstop)
{
write_npos();
utility.sleep(500);
breakwhile = true;

for(int i=0;i<nstartpos.length;i++)
{
if(!filesplitterfetch[i].bdownover)
{
breakwhile = false;
break;
}
}
if(breakwhile)
break;


//count++;
//if(count>4)
// sitestop();
}


system.err.println("文件下载结束！");
}
catch(exception e){e.printstacktrace ();}
}


//获得文件长度
public long getfilesize()
{
int nfilelength = -1;
try{
url url = new url(siteinfobean.getssiteurl());
httpurlconnection httpconnection = (httpurlconnection)url.openconnection ();
httpconnection.setrequestproperty("user-agent","netfox");


int responsecode=httpconnection.getresponsecode();
if(responsecode>=400)
{
processerrorcode(responsecode);
return -2; //-2 represent access is error
}

string sheader;

for(int i=1;;i++)
{
//datainputstream in = new datainputstream(httpconnection.getinputstream ());
//utility.log(in.readline());
sheader=httpconnection.getheaderfieldkey(i);
if(sheader!=null)
{
if(sheader.equals("content-length"))
{
nfilelength = integer.parseint(httpconnection.getheaderfield(sheader));
break;
}
}
else
break;
}
}
catch(ioexception e){e.printstacktrace ();}
catch(exception e){e.printstacktrace ();}

utility.log(nfilelength);

return nfilelength;
}

//保存下载信息（文件指针位置）
private void write_npos()
{
try{
output = new dataoutputstream(new fileoutputstream(tmpfile));
output.writeint(nstartpos.length);
for(int i=0;i<nstartpos.length;i++)
{
// output.writelong(npos[i]);
output.writelong(filesplitterfetch[i].nstartpos);
output.writelong(filesplitterfetch[i].nendpos);
}
output.close();
}
catch(ioexception e){e.printstacktrace ();}
catch(exception e){e.printstacktrace ();}
}

//读取保存的下载信息（文件指针位置）
private void read_npos()
{
try{
datainputstream input = new datainputstream(new fileinputstream(tmpfile));
int ncount = input.readint();
nstartpos = new long[ncount];
nendpos = new long[ncount];
for(int i=0;i<nstartpos.length;i++)
{
nstartpos[i] = input.readlong();
nendpos[i] = input.readlong();
}
input.close();
}
catch(ioexception e){e.printstacktrace ();}
catch(exception e){e.printstacktrace ();}
}

private void processerrorcode(int nerrorcode)
{
system.err.println("error code : " + nerrorcode);
}

//停止文件下载
public void sitestop()
{
bstop = true;
for(int i=0;i<nstartpos.length;i++)
filesplitterfetch[i].splitterstop();

}
}
/*
**filesplitterfetch.java
*/
package netfox;

import java.io.*;
import java.net.*;

public class filesplitterfetch extends thread {

string surl; //file url
long nstartpos; //file snippet start position
long nendpos; //file snippet end position
int nthreadid; //thread´s id
boolean bdownover = false; //downing is over
boolean bstop = false; //stop identical
fileaccessi fileaccessi = null; //file access interface

public filesplitterfetch(string surl,string sname,long nstart,long nend,int id) throws ioexception
{
this.surl = surl;
this.nstartpos = nstart;
this.nendpos = nend;
nthreadid = id;
fileaccessi = new fileaccessi(sname,nstartpos);
}

public void run()
{
while(nstartpos < nendpos && !bstop)
{

try{
url url = new url(surl);
httpurlconnection httpconnection = (httpurlconnection)url.openconnection ();
ht