java.net.HttpURLConnection:large file to upload

hello,
I want to upload large file to my sever,idea:set a maxmalChunkSize ,split file in chunks ,e.g. 5M file split in 2M,2M,1M and write into outputstream, server side received the chunks of a file,and write into a empty file in order to merge all of the chunks.
but I met some problem. during the uploding, the server respons only the last chunk of the file,that is: only the last chunk of the file is uploaded,the rest chunks are not.i dont know why. Is anybody could help me,that would be nice.thanks a lot!

code:

Code :

public boolean openConnection(String numberOfFiles,String type) {
 
 
       try{
            this.numberOfFiles = numberOfFiles;
            //this.connect = new URL("http://127.0.0.1/bdb/bdb_create.php");
            this.connection=(HttpURLConnection)(this.connect.openConnection());
 
            this.connection.setDoInput(true);
            this.connection.setDoOutput(true);
            this.connection.setUseCaches(false);
 
            this.connection.setRequestMethod("POST");
            this.connection.setRequestProperty("Connection", "Keep-Alive");
 
            System.out.println("#########################OPEN CONNECTION...connected...################################");  
            System.out.println(type+"; boundary=******");
 
            this.connection.setRequestProperty("Content-Type",type+";boundary=******");
 
            this.fileOut = new DataOutputStream(this.connection.getOutputStream());
 
        }
        catch(MalformedURLException ie){
            return false;
        }//ie.printStackTrace();}
 
        catch (ProtocolException ex) {
            System.out.println(ex);
        }
 
        catch (IOException ioex) {
            System.out.println(ioex);
        }
 
        return true;
    }
 
private final static int BUFLEN = 4096;
 
 
    private final byte readBuffer[] = new byte[BUFLEN];
 
    public boolean submitChunks(File fileName){
        try{
            this.uploadRemainingLength = this.getUploadLength(fileName);
            this.fileSize = this.getUploadLength(fileName);
 
            System.out.println("=>Original filesize= "+this.fileSize);
 
            boolean bLastChunk = false;
            int chunkPart = 0;
            long contentLength = 0;
            long thisChunkSize = 0;
            //int chunkCount = 0;
 
            //bChunkEnabled=1
            this.fileOut.writeBytes("--" + "******" + "\r\n");
            this.fileOut.writeBytes("Content-Disposition: form-data;name=\"bChunkEnabled\""+"\r\n");
            this.fileOut.writeBytes("\r\n");
            this.fileOut.writeBytes("1");
            this.fileOut.writeBytes("\r\n");
 
            System.out.println("--" + "******" + "\r\n");
            System.out.println("Content-Disposition: form-data;name=\"bChunkEnabled\""+"\r\n");
            System.out.println("\r\n");
            System.out.println("1");
            System.out.println("\r\n");
 
            while(!bLastChunk){
                chunkPart = chunkPart +1;
                bLastChunk = (contentLength > this.getRemainingLength(fileName));
                if(bLastChunk){
                    thisChunkSize = this.getRemainingLength(fileName);
 
                    System.out.println("@=>this is the last chunk part "+chunkPart+", " +
                            "chunkpart size= "+thisChunkSize+" uploading...");
                    System.out.println("insgesamt "+chunkPart+" chunks");
 
                }else{
                    thisChunkSize = this.maxChunkSize;
 
                    System.out.println("@=>this is the chunkpart "+chunkPart+", chunkpart size= "+maxChunkSize+" uploading...");
                }
                contentLength = thisChunkSize;
 
                //chunkPart
                this.fileOut.writeBytes("--" + "******" + "\r\n");
                this.fileOut.writeBytes("Content-Disposition: form-data;name=\"chunkPart\"" + "\r\n");
                this.fileOut.writeBytes("\r\n");
                this.fileOut.writeBytes(Integer.toString(chunkPart));
                this.fileOut.writeBytes("\r\n");
 
                System.out.println("--" + "******" + "\r\n");
                System.out.println("Content-Disposition: form-data;name=\"chunkPart\"" + "\r\n");
                System.out.println("\r\n");
                System.out.println(Integer.toString(chunkPart));
                System.out.println("\r\n");
 
                //bLastChunk
                this.fileOut.writeBytes("--" + "******" + "\r\n");
                this.fileOut.writeBytes("Content-Disposition: form-data;name=\"bLastChunk\"" + "\r\n");
                this.fileOut.writeBytes("\r\n");
                this.fileOut.writeBytes(String.valueOf(bLastChunk));
                this.fileOut.writeBytes("\r\n");
 
                System.out.println("--" + "******" + "\r\n");
                System.out.println("Content-Disposition: form-data;name=\"bLastChunk\"" + "\r\n");
                System.out.println("\r\n");
                System.out.println(String.valueOf(bLastChunk));
                System.out.println("\r\n");
 
                //file data
                this.fileOut.writeBytes("--" + "******" + "\r\n");
                this.fileOut.writeBytes("Content-Disposition: form-data;name=\""+this.numberOfFiles+"\";"
                  + " filename=\"" + fileName.toString() +"\"" + "\r\n");
                this.fileOut.writeBytes("\r\n");
 
                System.out.println("--" + "******" + "\r\n");
                System.out.println("Content-Disposition: form-data;name=\""+this.numberOfFiles+"\";"
                          + " filename=\"" + fileName.toString() +"\"" + "\r\n");
                System.out.println("\r\n");
 
 
                this.fileIn = new FileInputStream(fileName);
 
                int amount = (int)(thisChunkSize);
 
 
                while(amount > 0){
                    int toread = (amount > BUFLEN) ? BUFLEN : (int) amount;
                    int towrite = 0;
 
                    try{
                        towrite = this.fileIn.read(this.readBuffer,0,toread);
                    }catch (IOException e) {
                        e.printStackTrace();
                     }
 
                    if(towrite > 0){
                        try{
                            fileOut.write(this.readBuffer,0,towrite);
                            amount = amount - towrite;
                            this.uploadRemainingLength = this.uploadRemainingLength - towrite;
 
                            System.out.println("->write into outputstream: "+towrite
                                        +" || the left to be uploading: "+amount);
                        }catch (IOException ioe) {
                                ioe.printStackTrace();
                         }
 
 
                    }
 
                }
 
                this.fileOut.writeBytes("\r\n");
                this.fileOut.writeBytes("--" + "******" +"--"+"\r\n");
 
                System.out.println("\r\n");
                System.out.println("--" + "******" +"--"+"\r\n");
 
                this.fileOut.flush();
                this.fileIn.close();
 
 
 
            }//end while
 
 
        } catch (IOException ex) {ex.getStackTrace();}
 
        BufferedReader input;
        //DataInputStream input;
        try {
            input = new BufferedReader(new InputStreamReader(this.connection.getInputStream()));
            //input = new DataInputStream(this.connection.getInputStream());
            String out="";
 
            while(out!=null) {
 
                out = input.readLine();
                System.out.println("response:"+out);
            }
 
            input.close();
        } catch (IOException e) {e.printStackTrace();}
 
 
        return true;
    }

debug output:

Code :

#########################OPEN CONNECTION...connected...################################
multipart/form-data; boundary=******
A.filesize bigger than maxchunksize,we use chunk upload
=>Original filesize= 36192
--******
 
Content-Disposition: form-data;name="bChunkEnabled"
 
 
 
1
 
 
@=>this is the chunkpart 1, chunkpart size= 20000 uploading...
--******
 
Content-Disposition: form-data;name="chunkPart"
 
 
 
1
 
 
--******
 
Content-Disposition: form-data;name="bLastChunk"
 
 
 
false
 
 
--******
 
Content-Disposition: form-data;name="10"; filename="/home/i6stud/sijitang/Desktop/demo/export_bilder_10/export_bilder/5.jpg"
 
 
 
->write into outputstream: 4096 || the left to be uploading: 15904
->write into outputstream: 4096 || the left to be uploading: 11808
->write into outputstream: 4096 || the left to be uploading: 7712
->write into outputstream: 4096 || the left to be uploading: 3616
->write into outputstream: 3616 || the left to be uploading: 0
 
 
--******--
 
@=>this is the last chunk part 2, chunkpart size= 16192 uploading...
insgesamt 2 chunks
--******
 
Content-Disposition: form-data;name="chunkPart"
 
 
 
2
 
 
--******
 
Content-Disposition: form-data;name="bLastChunk"
 
 
 
true
 
 
--******
 
Content-Disposition: form-data;name="10"; filename="/home/i6stud/sijitang/Desktop/demo/export_bilder_10/export_bilder/5.jpg"
 
 
 
->write into outputstream: 4096 || the left to be uploading: 12096
->write into outputstream: 4096 || the left to be uploading: 8000
->write into outputstream: 4096 || the left to be uploading: 3904
->write into outputstream: 3904 || the left to be uploading: 0
 
 
--******--
 
response:<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
response:    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
response:<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="de" lang="de">
response:  <head>
response:    <title>FAU-Bilddatenbank::FAU-Bilddatenbank</title>
response:	<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
response:	<meta name="Language" content="Deutsch" />
response:...
...
response:</html>
response:null
#############################DISCONNECTED##################################### 0