How to serialize ArrayList of objects?

Question

I want to serialize an arraylist of Item but it doesn't work....

my Item class extends Stuff class and has some subclasses.

all of my classes implement Serilalizable.

i have this part :

try{
// Serialize data object to a file
ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("MyData.ser"));
out.writeObject(myData);
out.close();

// Serialize data object to a byte array
ByteArrayOutputStream bos = new ByteArrayOutputStream() ;
out = new ObjectOutputStream(bos) ;
out.writeObject(myData);
out.close();

// Get the bytes of the serialized object
byte[] buf = bos.toByteArray();
} catch (IOException e) {
}

my classes :

public class Stuff implements Serializeable{
....
some protected fields
.
.
}

public class Item extends Stuff implements Serializable{
...
..
.
} and some subclasses of Item:

public class FirstItem extends Item implements Serializable{
...
}

public class SecondItem extends Item implements Serializable{
...
} ... I want to serialize an object contains ArrayList of <Item> that has objects of Item's subclasses (FirstItem,SecondItem,...)

i think informations are sufficient...

it's just a little mistake and now works correctly... I'm sorry for my stupid question.

Thank you for your answers.

Could you please post the code you tried but didn't work, so we will be able to answer your question more specifically. — slaadvak, May 21 '14 at 21:14
How do you serialize it (what libraries do you use)? And what your classes are looking like? What do you need to serialize in them? And what does "doesn't work" means? — Dmitry Ginzburg, May 21 '14 at 21:14
Duplicate of http://stackoverflow.com/questions/8785955/serialization-arraylist-java — Anubian Noob, May 21 '14 at 21:14
Please #define "doesn't work". Does it throw an exception? Deserialize to nonsense? Set fire to your pants? — thkala, May 21 '14 at 21:15
Code added. i use java.io.Serializable class and without that ArrayList i can serialize my object. — armin.mohammadi, May 22 '14 at 06:02

Sardor I. · Accepted Answer · 2014-05-21T21:31:32.733

You can serialize class of ArrayList like this

public class MyData implements Serializable {

    private long id;
    private String title;
    private ArrayList<String> tags;
    ...

    public String getTitle() {
    }
}

And to create serializable

    ArrayList<MyData> myData = new ArrayList<MyData>();

try{
    // Serialize data object to a file
    ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("MyData.ser"));
    out.writeObject(myData);
    out.close();

    // Serialize data object to a byte array
    ByteArrayOutputStream bos = new ByteArrayOutputStream() ;
    out = new ObjectOutputStream(bos) ;
    out.writeObject(myData);
    out.close();

    // Get the bytes of the serialized object
    byte[] buf = bos.toByteArray();
} catch (IOException e) {
}

Why don't you need to set the ID of each list? – Jürgen K. Dec 14 '15 at 10:49 — Jürgen K., Dec 14 '15 at 10:49

score 1 · Answer 2 · answered May 21 '14 at 21:22

I'm taking a leap here that you are trying to serialize to something like json?

if so, you can use jackson (http://jackson.codehaus.org/)

final ObjectMapper mapper = new ObjectMapper();
try
{
    final String jsonString = mapper.writeValueAsString( _integrationSettings );
    // do something with the string...
}
catch( IOException e )
{
    // use a logger to output error
}

You can also deserialize with jackson as well...

A more detailed example here: http://blog.inflinx.com/2012/05/10/using-jackson-for-javajson-conversion/

Note: you can do similar for XML.

How to serialize ArrayList of objects?

2 Answers2

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