NIO and object serialization

I try to use the new IO API to implement a non-blocking multi-threaded server that communicates with client applications by exchanging serialized objects. I started from the code in the JavaWorld article at http://www.javaworld.com/javaworld/jw-09-2001/jw-0907-merlin.html .
With the new features of J2SDK 1.4.0, you don't have to create a separate thread per connected client. That is a big improvement.
But when I read an object with ObjectInputStream, I get a java.nio.channels.IllegalBlockingModeException.
Has anybody successfully implemented such a server since the release of the new io API?
Thanks.
Jean-Robert

Hi,
I tried to decode it and reconstruct the object as follows:
buffer.flip();
// Decode buffer
decoder.decode(buffer, charBuffer, false);
// Display
charBuffer.flip();
String str = charBuffer.toString();
try
     ByteArrayInputStream bis = new ByteArrayInputStream(str.getBytes());
     ObjectInputStream ois = new ObjectInputStream(bis);
     Object obj = ois.readObject();
     if (obj != null)
     System.out.println(obj.getClass().getName());
     System.out.println("Construction successful");
catch (Exception e)
     e.printStackTrace();
I think it is constructing the object. But it gave me the following exception:
java.io.InvalidClassException: MessageValueObject; local class incompatible: stream classdesc serialVersionUID = -1062950779601993928, local class serialVersionUID = -1038743931604855240
     at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:454)
     at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1511)
     at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1425)
     at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1616)
     at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1264)
     at java.io.ObjectInputStream.readObject(ObjectInputStream.java:322)
     at com.csxwt.zodiac.client.common.NIOPushletClient.run(NIOPushletClient.java:254)
     at java.lang.Thread.run(Thread.java:536)
Whe I compared the bytes of returned object with the actual object I noticed that two bytes were different from the orignal. They were replaced with '?' (byte code 063) in the reconstructed byte stream.
If anybody have a clue please help me too

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Servlet and Object Serialization

Hi,
I am developing a routing server in Java
2 Instances of the same server will be running in 2 different data centers.
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Server 1 will use a GET method to talk to the Server 2 -> Servlet which will write the state of an object back which will read by Server 1 and reconstruct the object back.
Do you find any issues in Object Serialization/DeSerialization in the Servlet.
What are the factors that I need to consider in this case?
Regards,
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Make sure that your servlet handles the transaction in the same thread that doPost() or doGet() is called in.
I ended up porting some old ServerSocket based code to a servlet, and was handing off the request and response objects to a handler thread on the server side. I ended up with a ton of intermittent errors like this.
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EOFException and Object Serialization

Hello, I am trying to build a distributed file storing system by using Multicast Sockets and I experience a problem the past 2 days.
I have to use multicast sockets because it is not my decision.
The problem appears when i have to transfer a file between 2 machines via UDP Datagrams.
I know that the size of the byte array that is contained in a datagram is quite small so I built a function that breaks the file in to small byte arrays that have the size of 9500 bytes each.
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You can get negative bytes in an object stream.
Try ensuring you have sent the length of the data and the data has been received in the correct order. Note Datagrams don't guarentee the order that packets were sent is the order they will be received.
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JMS and object serialization

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public class PMLCommandDTO implements Serializable {
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Cross post, already being responded in
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Servlets and Object Serialization

Say, you have a Servlet which sends Objects across an ObjectOutputStream which is obtained from its corresponding HttpServletResponse.
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From what I observe it is impossible to obtain an ObjectInputStream from the URLConnection of the calling servlet until it is finished processing.
Does anyone know if there is a way to do this?
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hi , I made a similar query some time ago and came up with the following solution.
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The servlet would read this in as follows:
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               if(test_ instanceof String){
                    System.out.println("String value is: "+test_);
               } else {
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this should give you the basic idea how to pass objects through http.
Hope it helps
rob

Error publishing plsql webservice (xml schema mapping and/or serializer)

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Duplicate of https://forums.oracle.com/thread/2610823
Timo

2D objects Serialization problem

Welcome!
I'm making a net game using RMI and I have this problem.
When I'm trying to join my client with the server an error occures:
Error: error marshalling arguments; nested exception is:
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My client contains an Object extending a JPanel class. There are 2D object used to make the map, and that's why this error occures.
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please help me... I have little time to finish my project, and this thing is blocking my work.
Big thanks to anybodey who will help.
regards floW

I'll tel u the whole story then, my problem is as follows:
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class BounceFrame extends JFrame{
public BounceFrame()
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private mgClient client;
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Regards floW

Byte [] to Object and Object to byte[]

Hi,
I am quite new to java and need some help. My question is how can I convert an Object to byte [] and convert back from byte [] to Object.
I was thinking of something like:
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byte [] object_byte=object.toString().getBytes();
When I try to do:
String obj_string=object_byte.toString();
But obj_string is not even equal to object.toString().
Any suggestions?
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well nnneil, if you try to convert and Object into a byte[] in that way you only convert the string representation of the object in bytes.
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Or if your problem if pass something like {0x01,0x02,0x0f,...} in an object you can use a simple casting over your variable.
try with this:
public class Main
public static void main(String[] args)
try
byte[] bs = {0x00,0x00,0x00};
Object o = (Object)bs;
System.out.print("Object:[" + o.toString() + "]");
System.out.print("<- That does not equals to ->");
int i = 0;
while(i < bs.length)
System.out.print("[" + bs[i++] + "]");
catch(Exception e){
e.printStackTrace();
output is: Object:[[B@df6ccd]<- That does not equals to ->[0][0][0]
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Customizing Forte object serialization

Forte supports serialization of arbitrary object graphs into streams.
However, there do not seem to be any well documented ways to customize
this serialization, e.g. by using a different encoding scheme. It would
seem there must be some support in there somewhere. I suppose at the
very least, one could parse a serialized object (once one decoded the
Forte encoding scheme) and do the conversion from that. That seems
suboptimal, though.
Has anyone done this? Any thoughts on how it might be done?
Regards,
Coty
To unsubscribe, email '[email protected]' with
'unsubscribe forte-users' as the body of the message.
Searchable thread archive <URL:http://pinehurst.sageit.com/listarchive/forte>

JavaFunda wrote:
Object serialization is the process of saving an object's state to a sequence of bytes. Does it saves only the instance variable or also the object methods(like getter and setter methods) ? Only the state--the instance variables. It doesn't save the class definition. That has to be available separately (via classloader) at deserilaization time. In other words, you cannot deserialize an instance of a class that is not on your classpath.
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Does we write the java object to text file only duuring serialization?We write the objects to wherever the other end of the ObjectOutputStream is connected to. Just like any other I/O.

Runtime Object serialization

Hi,
Could someone explain the concept of Runtime Object Serialization with a simple example?
Thanks

import java.io.*;
/* you NEED to make the class implement Serializable */
class Client implements Serializable {
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    private String address;
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Dumping the binary file you get this:
0000    AC ED 00 05 73 72 00 06 43 6C 69 65 6E 74 F1 D7   ....sr..Client..
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0020    65 73 73 74 00 12 4C 6A 61 76 61 2F 6C 61 6E 67   esst..Ljava/lang
0030    2F 53 74 72 69 6E 67 3B 4C 00 04 6E 61 6D 65 71   /String;L..nameq
0040    00 7E 00 01 78 70 74 00 24 31 20 49 6E 66 69 6E   .~..xpt.$1 Infin
0050    69 74 65 20 4C 6F 6F 70 3B 20 43 75 70 65 72 74   ite Loop; Cupert
0060    69 6E 6F 2C 20 43 41 20 39 35 30 31 34 74 00 0A   ino, CA 95014t..
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Object serializable?

Hi,
When writing a vector of my own objects out to a file, do the objects need to be serializable even though it is actually the vector I am outputting?
Also, each of my objects in this vector have a field that is a vector of other objects...do I need to declare those objects serializable also?

I think you still need to implement serializable on objects contained in the vector. I tried serializing a hashmap and my hashmap contained objects which needed to be serialized before the hashmap could be stored in a file.

Object serialization failure during OutOfMemory error (EOFException)

Hello all,
We are seeing a very strange situation when writing a serializable object to a flat file, specifically during an OutOfMemory condition. Our application saves the state of an object if an error occurs, and retries at a later point by reviving the object from its serialized form. We recently encountered a series of EOFExcetions when trying to reload the serialized object. Looking at the serialized data, we see that the file is indeed incomplete, and that it appears to be the serialized representation of the data contained within the object that is missing (the structure of the object appears to be stored in the serialized file, but not the runtime data).
The code that produces and consumes these serialized objects is used in a variety of locations, and even in the case where these EOF errors occurred usually works as expected. The difference appears to be that the error condition which lead to the object serialization was in-fact an OutOfMemory error. That is, we had an OOM error elsewhere in our application, which caused our objects to be serialized to disk. During this serialization process we end up with corrupt (incomplete) serialization data.
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jasonpolites wrote:
So.. the question is: Is it possible that the OutOfMemory situation causes the JVM to incorrectly serialize an object (without an error), and specifically to omit runtime data (variables) from the serialized form of the object?you're sure that the serialization process completed without an error? how do you know the the OOME did not cause the serialization to fail (because the serialization process itself will require more memory, hence if it is happening while the system is near the memory peak, it is likely to fail as well)? generally, when a jvm starts throwing OOME's all bets are off. failures in random places can easily cause the whole internal state of a system to become invalid.

Object serialization EOFException

Essentially what I want to do is write to an object to a file. The program can terminate and then when I start the program again, it will read the object from the file and restore the program's original state before it was terminated.
I get an EOFException with this code
//insert code that gets input which will be stored in a hashtable
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Sorry, I led you to believe that the actual class itself was going to be written to a file. I meant to say that the Hashtable in the class should be written to a file and then later on when I start the program again, it will restore the Hashtable to it's original state.
My writing coding is something like this:
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Communication between javascript and Objective-c in iOS.

We wanted to have a communication between javascript and objective c code. We have already tried the below approach.
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https://developer.apple.com/library/mac/documentation/AppleApplications/Conceptu al/SafariJSProgTopics/Tasks/ObjCFromJavaScript.html

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TCG

Sorry. should have elaborated more.
In SQLPLUS, (logged in while logged into my Linux OS), I am working to try and get sqlplus to display the results of my query so it is easy to read. Right now, it just displays using the first 1/4 or 1/3 of the monitor screen to the left. Make sense? So it does not stretch the results out to utilize the full screen. it is hard to break down and read the results because they are "stacked" on top of each other.
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Jason

NIO and object serialization

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