Serialized objects into Strings

poeta_boy · 07-14-2005, 08:20 PM

Hello:

I have read that I can write a Java object and transform it into an Stream, so to write it into a file. I have:

Code:

public class Guy implements Serializable
{
     private String name;

      public Guy()
     {
            super();
            name = "me";
      }

      public String toString(){ return "Hey it's " + name; }
}

and then I can do this:

Code:

// put it into the file
FileOutputStream out = new FileOutputStream("serial.txt");
ObjectOutputStream s = new ObjectOutputStream(out);
s.writeObject(new Guy() );

// read it from the file

FileInputStream in = new FileInputStream("serial.txt");
ObjectInputStream reader = new ObjectInputStream(in);

Guy me = (Guy)reader.readObject();

System.out.println(me);

So in the file I basically have an String.... I was wondering, can I get that String without reading it from a file, so I can store it in a Database, and I can read and write the object like TEXT, keeping its state? how to get the String that the method writeObject() will write in the file?

Thanks in advance

Poeta

http://www.novacreations.net

nadroj · 07-14-2005, 11:11 PM

am i getting what you want... you want to write actually text to a file rather than objects?
if so, you would use BufferedReader for input and PrintWriter for output.

when you create a bufferedreader you must put it in a try/catch statement. the bufferedreader takes in 1 parameter, which is a File object, which that takes in a parameter of a string to the filename.

also for the printwriter, it must be in a try/catch statement. it takes one parameter, which is a bufferedwriter which takes in 1 parameter which must be a filewriter which takes in 1 parameter for a file object which again takes a parameter for a string of the filename.

heres an example of the printwriter (bufferedwriter is shorter):

Code:

...
outFile = new PrintWriter(new BufferedWriter(new FileWriter(new File("/path/to/file"))));
...

from there, both are pretty easy to use. to read from the input file simply inFile.readLine() and to write to the output file use outFile.println()
check sun's site for the documentation for each so you know all the other methods that are available (i think theres stuff like .print() or .readInt() or something, i havent used it in months).

edit: also be sure that you close your IO files appropriately

poeta_boy · 07-14-2005, 11:19 PM

Hello:

thanks for your answer, but I believe I didn't quite explain myself ..... the:

FileOutputStream out = new FileOutputStream("serial.txt");
ObjectOutputStream s = new ObjectOutputStream(out);
s.writeObject(new Guy() );

gives me a file with a String in it, representing the serialization for that object right?, but my question is, how can I get that String, not in a file, but in a String datatype, maybe something like:

String serializedObject = something.Serialize(myObject);

I hope I did write well............ I kinda want a workaround in object persistence in databases.......... so if I have a group of objects, I could set them into Strings and save them in databases, and then retrieve them...

Thanks!

so I could save that String somewhere else, and then "deserialize" it

nadroj · 07-14-2005, 11:24 PM

are you just storing strings? if so then my above method will work

oh wait, no.. u said you were writting 'Guy's to the file, right?

your code:

Code:

FileOutputStream out = new FileOutputStream("serial.txt");
ObjectOutputStream s = new ObjectOutputStream(out);
s.writeObject(new Guy() );

DOESNT write a string to the file.. it writes an object of type Guy and stores it as binary data into the file. you cant then go read the file and extract just a string from it, because you dont know where it would be in the file or how long, etc.
you have to, as you did, read in the object and cast it to the type (Guy) then get whatever info you saved in the file, back by accessing the objects methods

edit: king crimson is great

poeta_boy · 07-14-2005, 11:28 PM

hey

so basicaly, I do need first the file, and then read it? hehehe mmmmmm while writting the serialized representation, will reading it as a file actually give me a valid String?

PS Yes!!! Matte Kudasai!

nadroj · 07-14-2005, 11:37 PM

i didnt understand that..
your first sentence, yes.. the next one, i dont get.

are you asking if you can just open the file, read its raw contents and extract from that what you are looking for? (which is a string or whatever, as you made it seem).
if so, the answer would be no.
try it yourself, open up a text editor and view the contents of your output file (serial.txt).. can you see the string in there? probably not. its binary data representing an object.
again, youll need to read this object first from the file, then using that object youll have to access whatever your looking for (string?) using it's methods (ie, myGuy.toString(), myGuy.getName().. whatever)

poeta_boy · 07-14-2005, 11:54 PM

hehehehe I did see the file and I do see a String.......... some readable, and some chars like squares...... mmmmmmmmm I was thinking I could override the object persistence so I could transform any given object and then save it in mySql in a Text variable.............. but I believe it can't be done =(

thanks!

nadroj · 07-15-2005, 12:00 AM

you wanted to store a java object in a SQL text variable?
and yes.. when you read the file, you will of course notice afew characters here and there that you know what they represent or would say, but thats because you _know_ what theyre supposed to say.. either way, its not the string.