How to marshall ArrayList

Question

I have a variable (list) of type ArrayList[] and I want to save it in XML. I tried JAXB, but it saves only the "" String (the repetition of " is equal to list.length) and no items in ArrayLists. If I tried the 2d array it works fine. If I tried ArrayList, it works also fine. How can I solve this problem?

My code is similar to:

@XmlRootElement
public class SomeClass {

    @XmlElement(name="part")
    private final ArrayList<Object>[] list;

    ... constructor, which fills the list variable

}

Can someone tell me how to do this? Please.

This answer might be relevant: http://stackoverflow.com/q/1603404/850326 — djhaskin987, Aug 16 '11 at 20:02

MByD · Answer 1 · 2011-08-17T08:14:55.190

2

You should not mix generic types with arrays - Look at Item 25 in Effective Java. Use 2D array or list of lists.

edited Aug 17 '11 at 08:14

answered Aug 16 '11 at 20:01

MByD

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I used this type (ArrayList – Matěj Polák Aug 16 '11 at 20:21
Thank you for explain me why I should not mix generic types and arrays. But if I used ArrayList> (list of lists) it is not still working. So I probably have to use XmlAdapter, but I dont now how to do this. – Matěj Polák Aug 17 '11 at 09:18

score 2 · Answer 2 · answered Aug 17 '11 at 15:13

Thank yout for your effort, but I finally found a solution :). I covered one list by another class and it's working fine.:

@XmlElement(name="part)
MyClass[] list;

@XmlRootElement
class MyClass {
    @XmlElement(name="item")
    ArrayList<Object> list;    
}

score 0 · Answer 3 · answered Aug 16 '11 at 20:21

0

Do you really need an array of list objects? If not you could also use two lists:

Private LinkedList<LinkedList<Object>> parts;

This works well with jaxb.

answered Aug 16 '11 at 20:21

rit

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Ok, I will use it, I just thought is not necessery to use list of lists :), because the length of the array is final (constant). – Matěj Polák Aug 16 '11 at 20:24
I think if you initialize the array list instead of the linked list, there should be no difference. – rit Aug 16 '11 at 20:34
I think so too. But I think it is not necessery to use ArrayList> if I can use ArrayList – Matěj Polák Aug 16 '11 at 20:39
So, I tried ArrayList>, but it is still not working. Can someone help me how to make it work? I just need a list of lists and save it with JAXB to XML. – Matěj Polák Aug 16 '11 at 21:05

3 Answers3