DataOutputStream writing too much
What I currently have
I'm currently trying to create a little download manager in Java and I have a problem with writing the loaded bytes in a file. I'm using a DataOutputStream
to write the byte-array which I read from a DataInputStream
. Here is the class I created to do that:
public class DownloadThread extends Thread{
private String url_s;
private File datei;
public DownloadThread(String url_s, File datei){
this.url_s = url_s;
this.datei = datei;
}
public void run(){
// Connect:
int size = 0;
URLConnection con = null;
try {
URL url = new URL(url_s);
con = url.openConnection();
size = con.getContentLength();
// Set Min and Max of the JProgressBar
prog.setMinimum(0);
prog.setMaximum(size);
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
// Download:
if (con != null || size != 0){
byte[] buffer = new byte[4096];
DataInputStream down_reader = null;
// Output:
DataOutputStream out = null;
try {
out = new DataOutputStream(new FileOutputStream(datei));
} catch (FileNotFoundException e1) {
e1.printStackTrace();
}
// Load:
try {
down_reader = new DataInputStream(con.getInputStream());
int byte_counter = 0;
int tmp = 0;
int progress = 0;
// Read:
while (true){
tmp = down_reader.read(buffer);
// Check for EOF
if (tmp == -1){
break;
}
out.write(buffer);
out.flush();
// Set Progress:
byte_counter += tmp;
progress = (byte_counter * 100) / size;
prog.setValue( byte_counter );
prog.setString(progress+"% - "+byte_counter+"/"+size+" Bytes");
}
// Check Filesize:
prog.setString("Checking Integrity...");
开发者_开发技巧 if (size == out.size()){
prog.setString("Integrity Check passed!");
} else {
prog.setString("Integrity Check failed!");
System.out.println("Size: "+size+"\n"+
"Read: "+byte_counter+"\n"+
"Written: "+out.size() );
}
// ENDE
} catch (IOException e) {
e.printStackTrace();
} finally{
try {
out.close();
down_reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
// Clean Up...
load.setEnabled(true);
try {
this.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
This is currently an inner-class and the prog
-Object is a JProgressBar
from it's mother-class, so it can be accessed directly.
Example
I'm trying to download the Windows .exe Version of the TinyCC, which should be 281KB size. The file i downloaded with my download manager is 376KB big.
The Output from the Script looks like this:
Size: 287181
Read: 287181
Written: 385024
So it seems that the read bytes match the file-size but there are more bytes written. What am I missing here?
This is wrong:
out.write(buffer);
It should be
out.write(buffer, 0, tmp);
You need to specify how many bytes to write, a read doesn't always read a full buffer.
Memorize this. It is the canonical way to copy a stream in Java.
int count;
while ((count = in.read(buffer)) > 0)
{
out.write(buffer, 0, count);
}
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