Why cant i append objects to a file

i'm amazed that i cannot append objects to a file
as i did earlier in c++
it gives StreamCorrupt error

Ashutosh.options4u wrote:
i'm amazed that i cannot append objects to a file
as i did earlier in c++Whatever you did in C++ didn't involve ObjectOutputStream or Java Serialization. You can append anything but objects to a file in Java. The reasons are two:
(a) ObjectOutputStream writes a header which ObjectInputStream expects to find at the beginning of the stream and nowhere else
(b) closing an ObjectOutputStream and starting a new one to append to the same file breaks the specified semantics for preservation of object graphs under Serialization, which can only be implemented within a single instance of ObjectOutputStream.
it gives StreamCorrupt errorI agree.

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How to append Objects in a file.

i have the following sample code ,
its not read data properly and throws Stream Corrupted Exception in the appended record. ( at Last statement of try block ).
Thanks,
import java.io.*;
public class IOError {
public static void main(String[] args) {
try {
ObjectOutputStream oos = new ObjectOutputStream(
new FileOutputStream("data.dat"));
oos.writeObject(new String("string 1"));
oos.writeObject(new String("string 2"));
oos.flush();
oos.close();
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("data.dat"));
System.out.println("----- Round 1 Starts ---------");
System.out.println((String) ois.readObject());
System.out.println((String) ois.readObject());
ois.close();
ObjectOutputStream oos2 = new ObjectOutputStream(
new FileOutputStream("data.dat",true)); // Appending Data
oos2.writeObject(new String("string 3"));
oos2.flush();
oos2.close();
ObjectInputStream ois2 = new ObjectInputStream(new FileInputStream("data.dat"));
System.out.println("----- Round 2 Starts ---------");
System.out.println((String) ois2.readObject());
System.out.println((String) ois2.readObject());
System.out.println((String) ois2.readObject()); // Stream Corrupted Exception
catch(Exception e) {
System.out.println(e);

Nasty. When you open an ObjectOutputStream, it will write a few initializing bytes, so if you really want to append objects to a file, then after you read the first two strings, you need to create a new ObjectInputStream that will read those bytes.
You could write an object indicating that now you are done with this ObjectOutputStream, so when you read the file and read this object, you know you have to create a new ObjectInputStream.
oos.writeObject(new String("string 1"));
oos.writeObject(new String("string 2"));
oos.writeObject(null); // null could be used if you know you won't write any other null's in your code.
//... append
oos.writeObject(new String("string 3"));
oos.writeObject(null);
// read:
FileInputStream fis = new FileInputStream("data.dat");
ObjectInputStream ois2 = new ObjectInputStream(fis);
String s;
while ((s = (String)ois2.readObject()) != null) {
System.out.println(s);
ois2 = new ObjectInputStream(fis);
while ((s = (String)ois2.readObject()) != null) {
System.out.println(s);

Appending objects in text file and searching.......

I have been trieng to implement simple search operation on the class objects stored in the text file. but when i try to append new objects in the same file and search for the same; java.io.StreamCorruptedException is thrown. wat the problem is, that wen i append to the text file; it stores some header information before the actual object is stored and on the deserialization, this header information is causing the exception. the same header information is stored every time, i append to the file. anybody knws hw to get past it??? my code is as given below:
package coding;
import java.io.BufferedReader;
import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.PrintWriter;
import java.io.Serializable;
     class Employee implements Serializable{
          private static final long serialVersionUID = 1L;
          String name;
          int id;
          public int getId() {
               return id;
          public void setId(int id) {
               this.id = id;
          public String getName() {
               return name;
          public void setName(String name) {
               this.name = name;
          public Employee(String name, int id) {
               this.name = name;
               this.id = id;
     public class FileSearch{
     public static void main(String[] args) throws IOException
          /*Entering the records into the file*/
          Employee ob = null;
          File file=new File("c:\\abc.txt");
          InputStreamReader isr=new InputStreamReader(System.in);
          BufferedReader stdin=new BufferedReader(isr);
          char fileExist='y';
          if(file.exists())
               System.out.println("File already exists!!!");
               System.out.println("Append New Records(press y) Or Search Existing File(press any other button)?:");
               String strTemp=stdin.readLine();
               fileExist=strTemp.charAt(0);
          else
               System.out.println("File doesnt exist; creating new file......");
          if(fileExist=='y')
               FileOutputStream fos=new FileOutputStream(file,true);
               ObjectOutputStream oos=new ObjectOutputStream(fos);
               char choice='y';
               System.out.println("Enter records:");
               while(choice=='y')
                    System.out.println("enter id:");
                    String id_s=stdin.readLine();
                    int id=Integer.parseInt(id_s);
                    System.out.println("enter name:");
                    String name=stdin.readLine();
                    ob=new Employee(name,id);
                    try
                         oos.writeObject(ob);
                         //count++;
                         oos.flush();
                    catch(Exception e)
                         e.printStackTrace();
                    System.out.println("Enter more records?(y/n)");
                    String str1=stdin.readLine();
                    choice=str1.charAt(0);
               oos.close();
          /*Searching for the record*/
          System.out.println("Enter Record id to be searched:");
          String idSearchStr=stdin.readLine();
          int idSearch=Integer.parseInt(idSearchStr);
          try
               FileInputStream fis=new FileInputStream(
                         file);
               ObjectInputStream ois=new ObjectInputStream(fis);
               int flag=1;
               FileReader fr=new FileReader(file);
               int c=fr.read();
               for(int i=0;i<c;i++)
                    Object ff=ois.readObject();
                    Employee filesearch=(Employee)ff;
                    if(filesearch.id==idSearch)
                         flag=0;
                         break;
               ois.close();
               if(flag==1)
                    System.out.println("Search Unsuccessful");
               else
                    System.out.println("Search Successful");
          catch(Exception e)
               e.printStackTrace();
}

966676 wrote:
All what I need to elect by who this word repeated. But I don't know really how to make It, maybe LinkedListYou should choose the simplest type fullfilling your needs. In this case I'd go for <tt>HashSet</tt> or <tt>ArrayList</tt>.
or I dont know, someone could help me?You need to introduce a variable to store the actual name which must be resetted if an empty line is found and then gets assigned the verry next word in the file.
bye
TPD

Appending Objects to a File using serialization

hi,
I was wondering if I can append objects in a single file. For example, suppose there are 2 .java files. 1st file creates the Serialized file caleed sl.dat, opens it, writes the object, close it down.
The 2nd file nw open that same file, sl.dat, in append mode, writes one more object and close it down.
next I want to read each object of the file. Will it work in this fashion?
I found a quite interesting discussion here. but it says that it is not possible.. is that true?
Any clue? Is there any other mean to achieve this?

arin wrote:
kajbj wrote:
I've done it by subclassing ObjectOutputStream. I could then add a constructor that took an argument that indicated if a header should be written or not.Can you explain what I need to done here... I have a class which extends ObjectOutputStream but what to do after that? What do u mean by header in the constructor?? Please help meYou do know that you have the source code for the class if you have a JDK? The source for ObjectOutputStream is in the src.zip.
The normal constructor calls writeStreamHeader, and that is the problem if you are going to append data since you don't want to get the stream header more than once. Create a constructor that takes a boolean as argument, and only calls writeStreamHeader if the boolean is true.
Kaj

Why doesn't "include/object/text from file" work?

I want to include (link) text from other Word documents to a main Word document and I use "include/object/text from file" (Word function)
It works fine when I do so in "H:", but doing exactly the same in the Sharepoint environement result in "nothing" (nothing happens)
It DOES work if I link from a document saved in Sharepoint to a "H:" - document, but that is of no use since I need all the documents to be stored in Sharepoint.
Guess it has to do with the set up och Sharepoint.
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Hi,
Did you mean insert a object in the documents?
Did you open the file with the local application or office web application?
In the office web application, it doesn’t have the function to insert a object in the browser.
I had tested with some word files in the library, open the word files with the local application, then insert file using the insert object function.
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What’s more, I had tested with Office 2010 and Office 2013, they all worked.
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Append Objects to a ObjectOutput Stream

i have opened a FileOutputStream(fis)(name,true) for appending and created a ObjectOutputStream with above fis. eventhough i am writing objects into file while reading i am only getting first object then i am getting StreamCorruptedException. why i am getting that exception and how to overcome my problem so that i can able to append object to existing file which holds objects?

In the append mode, the file header is writted twice (it seems to be a bug...)...
You must override the ObjectInputStream and the ObjectOutputStream to avoid the problem.
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public MyObjectOutputStream(OutputStream out) throws IOException {
super(out);
protected void writeStreamHeader() throws IOException {
// Nothing in header
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i couldnt think about any other title,as i am getting more and more confused.
this is what i know :
an object is "something" which has got some functionality && exists in memory (thats why real-world).
why cant we create objects of "only" methods ?
to be exact,i cant understand why java needs to put everything in the class?
eg.
public static void main(String args[])
int i;
i=i+5;
this method should be able to form an object, it has got both data members, and it can call another function to modify the data.
why do we NECESSARILY need to put this in a class ?

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dpux wrote:
i know its a design specification...but what advantage does it give ??
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It's also much easier to find functions that belong together grouped in a class.True, but if "global functions" had been allowed in Java, I bet you a doughnut they would have used package names as a name space, in exactly the same way this is done with classes and interfaces.
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Why cant I open a PDF file from a cd-r that I burned into this cd myself at work on my personal laptop? I have the same version of Adobe.

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Hi,
Tried to get some information around where ftp adapter stores the timestamp but couldnt find anything useful.
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Edited by: veejai24 on 11-Apr-2012 03:43

How to read appended objects from file with ObjectInputStream?

Hi to everyone. I'm new to Java so my question may look really stupid to most of you but I couldn't fined a solution by myself... I wanted to make an application, something like address book that is storing information about different people. So I decided to make a class that will hold the information for each person (for example: nickname, name, e-mail, web address and so on), then using the ObjectOutputStream the information will be save to a file. If I want to add a new record for a new person I'll simply append it to the already existing file. So far so good but soon I discovered that I can not read the appended objects using ObjectInputStream.
What I mean is that if I create new file and then in one session save several objects to it using ObjectOutputStream they all will be read with no problem by ObjectInputStream. But after that if in a new session I append new objects they won't be read. The ObjectInputStream will read the objects from the first session after that IOException will be generated and the reading will stop just before the appended objects from the second session.
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I am sorry for making this that long but I couldn't explain it more simple. If someone can give me a solution I'll be happy to hear it! ^.^ I'll also be glad if someone propose different approach of the problem! Here is the code:
import java.io.*;
class Fio
     public static void main(String[] args)
          try
               if (args[0].equals("w"))
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                    ObjectOutputStream oos = new ObjectOutputStream(fos);
                    for (int i = 2; i < args.length ; i++)
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               else if (args[0].equals("r"))
                    FileInputStream fis = new FileInputStream(args[1]);
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          catch (ClassNotFoundException exc)
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How to read appended objects from file with ObjectInputStream? The short answer is you can't.
The long answer is you can if you put some work into it. The general outline would be to create a file with a format that will allow the storage of multiple streams within it. If you use a RandomAccessFile, you can create a header containing the length. If you use streams, you'll have to use a block protocol. The reason for this is that I don't think ObjectInputStream is guaranteed to read the same number of bytes ObjectOutputStream writes to it (e.g., it could skip ending padding or such).
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Not trivial, but that's how you'd do it.

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It's easier to read your code (and help) when you use the code tags in you message...
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third it's best to show a StackTrace in case of an Exception, like thatcatch(Exception e)
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Why cant i append objects to a file

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