How to serialize/deserialize with DataOutputStream and DataInputStream?

Question

I'm trying to serialize/deserialize things with DataOutputSteam and DataInputSteam instead of ObjectInputStream/ObjectOutputStream.

The serialization fails. The txt file remains empty. Of course, the test2 strings are all empty in the end (can't deserialized an empty file).

Here is my object :

public class Test implements Serializable {
    public String[] nom;


    public Test() {

        nom = new String[5];
        nom[0] = "Coucou";
        nom[1] = "Je suis un tab de String";
        nom[2] = "Je vais me faire serialiser";
        nom[3] = "Et deserialiser aussi !";
        nom[4] = "Je suis le roi du monde !";
    } 
}

Here is my try :

    Test test = new Test();
    Test test2 = new Test();


    test2.nom[0] = "";
    test2.nom[1] = "";
    test2.nom[2] = "";
    test2.nom[3] = "";
    test2.nom[4] = "";

     DataInputStream dis;
     DataOutputStream dos;

   // serialisation manuelle
    try {
      dos = new DataOutputStream(
              new BufferedOutputStream(
                new FileOutputStream(
                  new File("nom2.txt"))));

      for(int i = 0; i < 5; i++)
      {  
             dos.writeUTF(test.nom[i]);
      } 
        } catch (FileNotFoundException e) {
    } catch (IOException e) {}      




    // deserialisation manuelle
       dis = new DataInputStream(
              new BufferedInputStream(
                new FileInputStream(
                  new File("nom2.txt"))));

    try { 
        test.nom[0] = dis.readUTF();
        test.nom[1] = dis.readUTF();
        test.nom[2] = dis.readUTF();
        test.nom[3] = dis.readUTF();
        test.nom[4] = dis.readUTF();
            } catch (FileNotFoundException e) {
    } catch (IOException e) {}

Try calling `dos.flush()` to write out the contents to the file before you start trying to read them back in. That's probably your problem. — childofsoong, May 18 '15 at 23:00
Serialized data is not text. The .txt filename extension is not appropriate. — user207421, May 26 '15 at 03:27

score 2 · Accepted Answer · edited May 23 '17 at 11:43

2

For a short explanation, calling dos.flush() will force the system to take anything buffered and actually write it to disk. For this reason, you need to call it before you try reading from the same file. For more details on flush(), I recommend looking at What is the purpose of flush() in Java streams? as this has been answered before.

edited May 23 '17 at 11:43

Community

1
1

answered May 18 '15 at 23:12

childofsoong

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23

score 0 · Answer 2 · answered May 19 '15 at 01:10

0

Try closing the output file before you open it for reading. On some systems e.g. Windows you won't succeed in the second open.

Closing it will flush the BufferedOutputStream.

answered May 19 '15 at 01:10

user207421

305,947
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How to serialize/deserialize with DataOutputStream and DataInputStream?

2 Answers2