Android  Analysis of the principle and example explanation of the continuous transmission of breakpoints

url url = new url("/android/");  
httpurlconnection httpconnection = (httpurlconnection)();  
//Set user-agent("user-agent","netfox");  
//Set the start position of the breakpoint continuous transmission("range","bytes=2000070");  
//Get input streaminputstream input = (); 
    The byte stream taken from the input stream is the file2000070The beginning of the byte stream。

    Everyone see，In fact, breakpoints continue to be transmittedjavaIt's still very simple to implement。

    The next thing to do is how to save the obtained stream into the file。

    Methods of saving files：I'm usingioIn the packagerandaccessfilekind。

    Very easy to operate，Assume from2000070Start saving files，The code is as follows：

JavaCode
randomaccess osavedfile = new randomaccessfile("","rw");  
long npos = 2000070;  
//Locate the file pointer to npos location(npos);  
byte[] b = new byte[1024];  
int nread;  
//Read the byte stream from the input stream and write it to the filewhile((nread=(b,0,1024)) > 0)  
{  
  (b,0,nread);  
} 
    How about it，It's very simple, too。

    The next thing to do is to integrate it into a complete program。Including a series of thread controls, etc.。

    three、Implementation of breakpoint continuous transmission kernel

    Mainly used6个kind，包括一个测试kind。

    Responsible for the capture of the entire file，Control internal threads（filesplitterfetchkind）。

    Responsible for crawling some files。

    Responsible for the storage of files。

    Information about the file to be crawled，Directory of file saved，name，Crawling filesurlwait。

    工具kind，Put some simple methods。

    测试kind。

    Four、Instance source code

    Below is the source program：

JavaCode
/* 
** 
*/ 
package netfox;  
import .*;  
import .*;  
  
public class sitefilefetch extends thread {  
  
siteinfobean siteinfobean = null; //File information beanlong[] nstartpos; //Start positionlong[] nendpos; //End Locationfilesplitterfetch[] filesplitterfetch; //Child thread objectlong nfilelength; //File lengthboolean bfirst = true; //Is the first time the file is retrievedboolean bstop = false; //Stop signfile tmpfile; //Temporary information on file downloaddataoutputstream output; //Output stream to file 
public sitefilefetch(siteinfobean bean) throws ioexception  
{  
siteinfobean = bean;  
//tmpfile =  ("zhong","1111",new file(()));  
tmpfile = new file(()+ + ()+".info");  
if( ())  
{  
bfirst = false;  
read_npos();  
}  
else 
{  
nstartpos = new long[()];  
nendpos = new long[()];  
}   
}  
  
public void run()  
{  
//Get file length//Split the file//Instance filesplitterfetch//Start the filesplitterfetch thread//Waiting for the child thread to returntry{  
if(bfirst)  
{  
nfilelength = getfilesize();  
if(nfilelength == -1)  
{  
("file length is not known!");  
}  
else if(nfilelength == -2)  
{  
("file is not access!");  
}  
else 
{  
for(int i=0;i<;i++)  
{  
nstartpos = (long)(i*(nfilelength/));  
}  
for(int i=0;i<-1;i++)  
{  
nendpos = nstartpos[i+1];  
}  
nendpos[-1] = nfilelength;  
}  
}  
//Starting child threadfilesplitterfetch = new filesplitterfetch[];  
for(int i=0;i<;i++)  
{  
filesplitterfetch = new filesplitterfetch((),  
() +  + (),  
nstartpos,nendpos,i);  
("thread " + i + " , nstartpos = " + nstartpos + ", nendpos = " + nendpos);  
();  
}  
// filesplitterfetch[-1] = new filesplitterfetch((),  
() +  + (),npos[-1],nfilelength,-1);  
// ("thread " + (-1) + " , nstartpos = " + npos[-1] + ",  
nendpos = " + nfilelength);  
// filesplitterfetch[-1].start();  
 
//Waiting for the child thread to end//int count = 0;  
//Whether loop endsboolean breakwhile = false;  
  
while(!bstop)  
{  
write_npos();  
(500);  
breakwhile = true;  
  
for(int i=0;i<;i++)  
{  
if(!)  
{  
breakwhile = false;  
break;  
}  
}  
if(breakwhile)  
break;  
  
//count++;  
//if(count>4)  
// sitestop();  
}  
  
("File download ends!");  
}  
catch(exception e){ ();}  
}  
  
//Get file lengthpublic long getfilesize()  
{  
int nfilelength = -1;  
try{  
url url = new url(());  
httpurlconnection httpconnection = (httpurlconnection) ();  
("user-agent","netfox");  
 
int responsecode=();  
if(responsecode>=400)  
{  
processerrorcode(responsecode);  
return -2; //-2 represent access is error  
}  
  
string sheader;  
  
for(int i=1;;i++)  
{  
//datainputstream in = new datainputstream( ());  
//(());  
sheader=(i);  
if(sheader!=null)  
{  
if(("content-length"))  
{  
nfilelength = ((sheader));  
break;  
}  
}  
else 
break;  
}  
}  
catch(ioexception e){ ();}  
catch(exception e){ ();}  
  
(nfilelength);  
  
return nfilelength;  
}  
  
//Save download information (file pointer location)private void write_npos()  
{  
try{  
output = new dataoutputstream(new fileoutputstream(tmpfile));  
();  
for(int i=0;i<;i++)  
{  
// (npos);  
();  
();  
}  
();  
}  
catch(ioexception e){ ();}  
catch(exception e){ ();}  
}  
  
//Read the saved download information (file pointer location)private void read_npos()  
{  
try{  
datainputstream input = new datainputstream(new fileinputstream(tmpfile));  
int ncount = ();  
nstartpos = new long[ncount];  
nendpos = new long[ncount];  
for(int i=0;i<;i++)  
{  
nstartpos = ();  
nendpos = ();  
}  
();  
}  
catch(ioexception e){ ();}  
catch(exception e){ ();}  
}  
  
private void processerrorcode(int nerrorcode)  
{  
("error code : " + nerrorcode);  
}  
  
//Stop file downloadpublic void sitestop()  
{  
bstop = true;  
for(int i=0;i<;i++)  
();  
}  
}  
/* 
** 
*/ 
package netfox;  
  
import .*;  
import .*;  
  
public class filesplitterfetch extends thread {  
  
string surl; //file url  
long nstartpos; //file snippet start position  
long nendpos; //file snippet end position  
int nthreadid; //threads 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  
{  
 = surl;  
 = nstart;  
 = nend;  
nthreadid = id;  
fileaccessi = new fileaccessi(sname,nstartpos);  
}  
  
public void run()  
{  
while(nstartpos < nendpos && !bstop)  
{   
try{  
url url = new url(surl);  
httpurlconnection httpconnection = (httpurlconnection) ();  
("user-agent","netfox");  
string sproperty = "bytes="+nstartpos+"-";  
("range",sproperty);  
(sproperty);  
  
inputstream input = ();  
//logresponsehead(httpconnection);  
  
byte[] b = new byte[1024];  
int nread;  
while((nread=(b,0,1024)) > 0 && nstartpos < nendpos && !bstop)  
{  
nstartpos += (b,0,nread);  
//if(nthreadid == 1)  
// ("nstartpos = " + nstartpos + ", nendpos = " + nendpos);  
}  
  
("thread " + nthreadid + " is over!");  
bdownover = true;  
//npos =  (b,0,nread);  
}  
catch(exception e){ ();}  
}  
}  
  
//Print the header of the responsepublic void logresponsehead(httpurlconnection con)  
{  
for(int i=1;;i++)  
{  
string header=(i);  
if(header!=null)  
//(header,(header));  
(header+" : "+(header));  
else 
break;  
}  
}  
  
public void splitterstop()  
{  
bstop = true;  
}   
}  
  
/* 
** 
*/ 
package netfox;  
import .*;  
  
public class fileaccessi implements serializable{  
  
randomaccessfile osavedfile;  
long npos;  
  
public fileaccessi() throws ioexception  
{  
this("",0);  
}  
  
public fileaccessi(string sname,long npos) throws ioexception  
{  
osavedfile = new randomaccessfile(sname,"rw");  
 = npos;  
(npos);  
}  
  
public synchronized int write(byte[] b,int nstart,int nlen)  
{  
int n = -1;  
try{  
(b,nstart,nlen);  
n = nlen;  
}  
catch(ioexception e)  
{  
 ();  
}  
  
return n;  
}   
}  
  
/* 
** 
*/ 
package netfox;  
  
public class siteinfobean {  
  
private string ssiteurl; //sites url  
private string sfilepath; //saved files path  
private string sfilename; //saved files name  
private int nsplitter; //count of splited downloading file  
  
public siteinfobean()  
{  
//default value of nsplitter is 5  
this("","","",5);  
}  
  
public siteinfobean(string surl,string spath,string sname,int nspiltter)  
{  
ssiteurl= surl;  
sfilepath = spath;  
sfilename = sname;  
 = nspiltter;   
}  
  
public string getssiteurl()  
{  
return ssiteurl;  
}  
  
public void setssiteurl(string value)  
{  
ssiteurl = value;  
}  
  
public string getsfilepath()  
{  
return sfilepath;  
}  
  
public void setsfilepath(string value)  
{  
sfilepath = value;  
}  
  
public string getsfilename()  
{  
return sfilename;  
}  
  
public void setsfilename(string value)  
{  
sfilename = value;  
}  
  
public int getnsplitter()  
{  
return nsplitter;  
}  
 
public void setnsplitter(int ncount)  
{  
nsplitter = ncount;  
}  
}   
 
/* 
** 
*/ 
package netfox;  
  
public class utility {  
  
public utility()  
{  
}  
  
public static void sleep(int nsecond)  
{  
try{  
(nsecond);  
}  
catch(exception e)  
{  
 ();  
}  
}  
  
public static void log(string smsg)  
{  
(smsg);  
}  
  
public static void log(int smsg)  
{  
(smsg);  
}  
}  
  
/* 
** 
*/ 
package netfox;  
  
public class testmethod {  
  
public testmethod()  
{ ///xx/weblogic60b2_win.exe  
try{  
siteinfobean bean = new siteinfobean("http://localhost/xx/weblogic60b2_win.exe","l:\\temp","weblogic60b2_win.exe",5);  
//siteinfobean bean = new siteinfobean("http://localhost:8080/","l:\\temp","weblogic60b2_win.exe",5);  
sitefilefetch filefetch = new sitefilefetch(bean);  
();  
}  
catch(exception e){ ();}   
}  
  
public static void main(string[] args)  
{  
new testmethod();  
}  
}