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How do I save an array list of serialized objects?

5 replies on 1 page. Most recent reply: Sep 14, 2003 7:55 PM by wdzwdz

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Flat View: This topic has 5 replies on 1 page
Laurence Bier

Posts: 8
Nickname: sandman99
Registered: Sep, 2003

How do I save an array list of serialized objects? Posted: Sep 11, 2003 7:48 PM
Reply to this message Reply
Advertisement
I currently trying this approach, because a more straightforward one keeps failing. A file is created, but no data is ever retrieved:

The save:

private void SaveCustomerData()
{

// customerDataList is the ArrayList
// used to save customer data to disk

try
{

ObjectOutputStream out=new ObjectOutputStream(new FileOutputStream(FILE_NAME));
for(int i=0;i<customerDataList.size();i++)
{
CustomerData customerDataItem=(CustomerData) customerDataList.get(i);
out.writeObject(customerDataItem);
}

out.close();

}

catch(Exception e)
{



}


}

The load:

private void GetCustomerDataFromDisk()
{

// used to retrieve customer data from disk

boolean errorTriggered=false;

try
{

ObjectInputStream in=new ObjectInputStream(new FileInputStream(FILE_NAME));
CustomerData[] customerDataItems=(CustomerData[]) in.readObject();
for(int i=0;i<customerDataItems.length;i++)
AddCustomerFromDisk(customerDataItems.getCustomerFirstName(),customerDataItems.getCustomerLastName(),customerDataItems.getCustomerID(),customerDataItems.ge tSavingsAccount(),customerDataItems.getCheckingAccount(),customerDataItems.get InvestmentAccount(),customerDataItems.getLineOfCreditAccount());

in.close();


}


...

etc.

}


Senthoorkumaran Punniamoorthy

Posts: 335
Nickname: senthoor
Registered: Mar, 2002

Re: How do I save an array list of serialized objects? Posted: Sep 11, 2003 10:27 PM
Reply to this message Reply
You are writing object by object to the file. Therefore when you are reading them back you have to read object by object. Therefore 
CustomerData[] customerDataItems=(CustomerData[]) in.readObject();

is not going to work. Since you are reading it trying to cast to a CustomerData[] array. It will fail at that point I guess.

One more thing when you said the straight approach failed what was your straight forward approach?

Laurence Bier

Posts: 8
Nickname: sandman99
Registered: Sep, 2003

Re: How do I save an array list of serialized objects? Posted: Sep 13, 2003 7:48 PM
Reply to this message Reply
My original try is below. I get an "incompatible types" error on the read.


// writing the data
// customerDataList is an arraylist

try
{

ObjectOutputStream out=new ObjectOutputStream(new FileOutputStream(FILE_NAME));

out.writeObject(customerDataList);

out.close();

}

catch(Exception e)
{



}

// reading the data


try
{

ObjectInputStream in=new ObjectInputStream(new FileInputStream(FILE_NAME));
customerDataList=in.readObject();
in.close();


}

Senthoorkumaran Punniamoorthy

Posts: 335
Nickname: senthoor
Registered: Mar, 2002

Re: How do I save an array list of serialized objects? Posted: Sep 13, 2003 9:18 PM
Reply to this message Reply 
customerDataList=(ArrayList)in.readObject();


Why don't you try this?

Laurence Bier

Posts: 8
Nickname: sandman99
Registered: Sep, 2003

Re: How do I save an array list of serialized objects? Posted: Sep 14, 2003 4:00 PM
Reply to this message Reply
Excellent! Very nice work - and so obvious!

wdzwdz

Posts: 3
Nickname: wdzwdz
Registered: Dec, 2002

Re: How do I save an array list of serialized objects? Posted: Sep 14, 2003 7:55 PM
Reply to this message Reply
//My example!
package objectserial.array;

import java.io.Serializable;

public class WDZObject implements Serializable {
public static void main(String[] args) {
}
public WDZObject(String sName,String sSex,int iAge){
this.name= sName;
this.age = iAge;
this.sex = sSex;
}
public int getAge() {
return age;
}
public String getName() {
return name;
}
public void setAge(int age) {
this.age = age;
}
public void setName(String name) {
this.name = name;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public String toString(){
return "name="+name+",sex="+sex+",age="+age;
}

private String name="wdz";
private int age=10;
private String sex;

}
////
package objectserial.array;

import java.io.*;
import java.util.*;

public class ArraySerial {
private String FILE_NAME = "e:/sss.txt";
private ArrayList array;

public ArraySerial() {
array = new ArrayList();
}

public void loadFromDisk() {
try {
ObjectInputStream in = new ObjectInputStream(new FileInputStream(
FILE_NAME));
array = (ArrayList)in.readObject();
}
catch (Exception e) {
}
}
public void printArrayList(){
for(int i =0;i<array.size();i++){
System.out.println("object "+i+"="+array.get(i));
}
}

private void SaveToDisk() {
WDZObject wdzObject = null;
for (int i = 0; i < 20; i++) {
wdzObject = new WDZObject("wdz"+i,"man", 80);
array.add(wdzObject);
}
try {
ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(
FILE_NAME));
/* out.writeObject(array);ºÍÏÂmainde ´úÂëµÈ¼Û
for (int i = 0; i < array.size(); i++) {
WDZObject customerDataItem = (WDZObject) array.get(i);
out.writeObject(customerDataItem);
}*/
out.writeObject(array);
out.close();
}

catch (Exception e) {
System.out.println("SaveToDisk error--"+e.getMessage());
}
}

public static void main(String[] args) {
ArraySerial a = new ArraySerial();
a.SaveToDisk();
a.loadFromDisk();
a.printArrayList();
}
}

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