serializing arrayList ? Help please

[tones1986]

Hey all -

I have created an ArrayList as follows:

ArrayList<Object> arList = new ArrayList<Object>();

The arraylist contains the following - every time it will have the same data ... either filled or considered "";

String - transaction type
String - name
String - ssn
String - address
int - code

How can i take this arrayList and seriliaze it, and pass it from a 'client' through sockets, to a 'server'?

I have read about this online all over the place - but as for now i have come up with something like:

ObjectOutputStream oos = new ObjectOutputStream();

But i get a precompile error here saying: "The constructor ObjectOutputStream() is not visible"

And i have no clue what that means...

I assume i create an output object, then do outObj.writeOut(arList):

Then on the server side use an input object and use:

io.readObject();

But i am still pretty clueless, if someone could open my eyes as to how this would be plausible - i would be very very appreciative!

[tones1986]

Current code looks like this now:
Client Side

System.out.println("All things filled - will call server with info");
			
sendInfoAr.add("ADD");
sendInfoAr.add(nameVal);
sendInfoAr.add(ssnVal);
sendInfoAr.add(addressVal);
sendInfoAr.add(codeVal);
		    
try{
System.out.println("Should now create and send serialized thing");
FileOutputStream fileOut = new FileOutputStream("something.ser");
ObjectOutputStream out = new ObjectOutputStream(fileOut);
out.writeObject(sendInfoAr);
out.close();
fileOut.close();
		        
} catch(FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}

Server Side:

ArrayList<Object> inputDataAr = new ArrayList<Object>();
userInfo readInUser = new userInfo();
 try {
System.out.println("Creating File/Object input stream...");
          
FileInputStream fileIn = new FileInputStream("something.ser");
ObjectInputStream in = new ObjectInputStream(fileIn);

System.out.println("Loading Hashtable Object...");
inputDataAr = (ArrayList)in.readObject();

System.out.println("Closing all input streams...\n");
 in.close();
fileIn.close();
          
} catch (ClassNotFoundException e) {
          e.printStackTrace();
      } catch(FileNotFoundException e) {
          e.printStackTrace();
      } catch (IOException e) {
          e.printStackTrace();
      }

System.out.println("Should print name: " + readInUser.name);

When i run my client, and enter values and store them into my arrayList, that part seems to work, but the server gives me this error:

Server listening on port 9704
Creating File/Object input stream...
java.io.FileNotFoundException: something.ser (No such file or directory)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.<init>(FileInputStream.java:106)
at java.io.FileInputStream.<init>(FileInputStream.java:66)
at Conversation.run(server.java:166)
Should print name:

Line 166 in server.java is this line of code:

FileInputStream fileIn = new FileInputStream("something.ser");

Anyone have any idea why the something.ser couldn't be found? Im confused by this - as im 99% sure my client does send this to the server!

Thanks for any help

[giri.pankaj]

Is this file "something.ser" already created before you try to read that using fileInputStream at the server's side?

[tones1986]

Alright - i have changed this thing up some. Instead of using an ArrayList ... i have implemented my own class to store the data, and i will attempt to serialize an object of that class - sending that to the server instead. This should give me better access etc to my values.

Here is what i have done:
server and client both have:

public class UserInfo implements Serializable {
String name, ssn, address, type, response, code;
public UserInfo() {
 name = ssn = address = type = code = response = "";
}
}

On the client side i create an instance of this class, then similar to previous attempts, i get the information from my GUI and store in the objects values. Here:

UserInfo addUser = new UserInfo();
...
...
addUser.name = nameVal;
addUser.address = addressVal;
addUser.ssn = ssnVal;
addUser.code = codeVal;

I then try to send this to the server as a serialized object:

System.out.println("Should now create and send serialized thing");
oos = new ObjectOutputStream(sock.getOutputStream());	    	
oos.writeObject(addUser); 		
oos.flush();   
oos.reset();
 }
catch(FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} // end try

I get the following error on the oos.WriteObject() line:
java.io.NotSerializableException:

Why would this be - initially i thought it was because i had 'code' as an int, and i read somewhere that ints donesn't implement serializable?

Any ideas/tips etc would be appreciated, thank you

[tones1986]

Okay - moving on - hopefully i can get another reply with this more simple question:

I have this code:

public void run()
  {  
// try connect to mysql database
//System.out.println("" + addUser.name + " " + addUser.ssn); 
try {
			
	ObjectInputStream ois = new ObjectInputStream(client.getInputStream());
	UserInfo addUser = null;// = new UserInfo();
	addUser = (UserInfo) ois.readObject();	
	System.out.println(addUser);
	ois.close();
			
if (addUser.type.equals("ADD"))
	{
	System.out.println("in here");
	addUser = addCustomer(addUser);
	}
	} catch (ClassNotFoundException e) {
	e.printStackTrace();
	} catch (IOException e2) {
	e2.printStackTrace();
	}
		
//oos.writeObject(addUser); //send updated info back to server
System.out.println("Closing all input streams...\n");
} 
// end run

This is in my server.java

In my client i have this:

try 
{
Socket sock = new Socket("turing.cs.niu.edu", 9704);
ObjectOutputStream oos = new ObjectOutputStream(sock.getOutputStream()); 

nameVal = tfName.getText();
ssnVal = tfSSN.getText();
addressVal = tfAddress.getText();
codeVal = tfCode.getText();
if (nameVal.equals(""))
{
tfName.setText("error - empty");
nameError.setText("EMPTY FIELD");
    System.out.println("empty name field");
}
if (ssnVal.equals(""))
tfSSN.setText("error - empty");
if (addressVal.equals(""))
tfAddress.setText("error - empty");
if (codeVal.equals(""))
tfCode.setText("error - empty");
else if (!nameVal.equals("") && !ssnVal.equals("") && addressVal.equals("") && !codeVal.equals("")) {
   System.out.println("All things filled - will call server with info");
   addUser.name = nameVal;
   addUser.address = addressVal;
   addUser.ssn = ssnVal;
   addUser.code = Integer.parseInt  (codeVal);
   addUser.type = "ADD";
   oos.writeObject(addUser); 
   oos.flush();
   oos.close();
   } // end else if
   } // end try
   catch (UnknownHostException uhe)
   {
    System.out.println("Unknown Host");
    }
    catch (IOException ioe)
    {
     System.out.println("IO error: " + ioe.getMessage());
     }
}

I get the following error:
java.io.StreamCorruptedException: invalid stream header: 7372000F

On this line of the server code:

ObjectInputStream ois = new ObjectInputStream(client.getInputStream());

Anyone have any ideas as to why this would happen?

thanks in advance

[JamesCherrill]

You often get "stream corrupted" during debugging when a previous test crashes part way thru and the socket/stream is left open and part-written or part-read. It's worth checking that there are no instances of the JVM still running from failed tests before starting the next test.
ps: You shouldn't have to write your own serialisation code for a class that just has serialisable members - I would go back to that version and find out why it didn't work.