Writting an object in a file. Best way

Question

I have a problem with time.

I currently develop an app in Java where I have to make a network analyzer.

For that I use JPCAP to capture all the packets, and write them in a file, and from there I will put them bulk in DB.

The problem is when I am writting in file the entire object, like this,

UDPPacket udpPacket = (UDPPacket)packet
wtf.writeToFile("packets.txt",udpPacket +"\n");

everything is working nice and smooth, but when I try to write like this

    String str=""+udpPacket.src_ip+" "+udpPacket.dst_ip+""
+udpPacket.src_port+" "+udpPacket.dst_port+" "+udpPacket.protocol +
" Wi-fi "+udpPacket.dst_ip.getCanonicalHostName()+"\n";
     wtf.writeToFile("packets.txt",str +"\n");

writting in file is during lot more time.

the function to write in file is this

public void writeToFile(String name, String str){
        try{
            PrintWriter writer = new PrintWriter(new FileOutputStream(new File(name),this.restart));
            if(!str.equalsIgnoreCase("0")){
                writer.append(str);
                this.restart=true;
            }
            else {
                this.restart=false;
                writer.print("");
            }
            writer.close();
        } catch (IOException e) {
          System.out.println(e);
        }
    }

Can anyone give me a hit, whats the best way to do this?

Thanks a lot

EDIT:

7354.120266 ns - packet print

241471.110451 ns - with StringBuilder

A couple of notes. First, doesn't the `getCanonicalHostName()` have to do a DNS resolve? Second, use a `StringBuilder` rather than all of the String concatinations. — KevinO, May 01 '17 at 21:35
With the function getCanonicalHostName() its not a problem, its almost working, the method extract some info from header, but isnt a big problem. using StringBuilder doesn't make any good. Time difference is also big, 7354.120266 ns - for packet print 241471.110451 ns - with StringBuilder — Paul F., May 01 '17 at 21:57
And the output contents when using the `udpPacket` write are the same as when you build the String? I don't have a working example at the moment to check. Side consideration: it may be more efficient to not open/close the file on every call to `writeToFile()`. — KevinO, May 01 '17 at 22:21
OK, I found the source code for UDPPacket. Its `.toString()` has `getSourceAddress()/getSourcePort()` and `getDestinationAddress()/getDestinationPort()` and some length information. I would suspect that something, such as `getCanonicalHostName()` is slow. I might suggest trying subsets of the output to verify the timing. — KevinO, May 01 '17 at 22:27
Well, even if I write only 2 attributes, such as destination ip and source ip, it also goes slow... so I dont think that's the problem — Paul F., May 01 '17 at 23:08

score 0 · Answer 1 · answered May 01 '17 at 23:43

0

Keep the PrintWriter open. Don't open and close it for every line you want to write to the file. And don't flush it either: just close it when you exit. Basically you should remove your writeToFile() method and just call PrintWriter.write() or whatever directly when necessary.

NB You are writing text, not objects.

answered May 01 '17 at 23:43

user207421

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Even if I make System.out.println(str) its working slowly. So I dont think this is the problem. But it's an improvement. Thanks – Paul F. May 02 '17 at 07:09
If it isn't the problem how can it possibly be an improvement? It is working as slowly as `System.out.println()`, which is going to be *very* slow in most cases, much slower than writing to an already-open file via a `Writer` that does application-side buffering. Your testing methodology is flawed. Try it my way. If there's still a problem you're entitled to assert this isn't the problem. Not before. – user207421 May 02 '17 at 09:43

score 0 · Answer 2 · answered May 02 '17 at 08:31

0

I found the problem

as @KevinO said, getCanonicalHostName() was the problem.

Thanks a lot.

answered May 02 '17 at 08:31

Paul F.

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Writting an object in a file. Best way

2 Answers2