Serializing a named list unintuitive

My use case is very simple, I have to create an XML document that has, among others, a list of “item” nodes with a parent “items” node. It could look like this:

<channel>
  <items>
    <item>...</item>
    <item>...</item>
  </items>
</chanell>

However, the naive approach of using a list/array cannot seem to produce this with any amount of configuration via annotations:

public class Channel
{
  public final List<Item> items = new ArrayList<>();
}

public class Item
{
}

// Produces: <channel><items><items></items>...</items></channel>

Ultimately, the only way I was able to create the output conforming to the schema from above was to create a useless wrapper class, turn off wrapping, and name my list nonsensically:

public class Channel
{
  public final Items items = new Items();
}

public class Items
{
  @JacksonXmlElementWrapper(useWrapping=false)
  public final List<Item> item = new ArrayList<>();
}

public class Item
{
}

// Produces: <channel><items><item></item>...</items></channel>

This does result in the correct output schema, but now I am forced to access my objects in a non-intuitive way. For instance, if I want to add an item to my list of items, I must call the following:

channel.items.item.add(new Item());

which looks like I am adding an Item to another Item, rather than the list of items.

What I expected to work but did not was the following:

public class Channel
{
  // with wrapping enabled, the parent node should be "<items>"
  public final List<Item> items = new ArrayList<>();
}

// Each Item instance should be rendered as "<item>"
@JacksonXmlRootElement(localName="item")
public class Item
{
}

This would allow me to access my data in a sane manner:

channel.items.add(new Item());

TL;DR - It seems to me that @JacksonXmlRootElement(localName="item") does not work on any object in a collection/array, and instead the localName of the collection is used for the parent node (correct) AND each object in the collection/array (incorrect).

[jacobharris919]

Have you tried this?

   public class Channel
   {
      @JacksonXmlElementWrapper(localName = "items")
      @JacksonXmlProperty(localName = "item")
      public final List<Item> items = new ArrayList<Item>();
    }

[jackygurui]

OK, I think I have found a solution:

public class Channel
{
  @JacksonXmlElementWrapper(useWrapping = false)
  @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.WRAPPER_OBJECT)
  public final List<Item> items = new ArrayList<Item>();
}

Which gives me exactly what I wanted:

<channel>
  <items>
    <pen>...</pen>
    <pencil>...</pencil>
    <paper>...</paper>
  </items>
</channel>

However I am not entirely sure if it is a bug that if I didn’t specify @JacksonXmlElementWrapper(useWrapping = false) I would end up with an output like this:

<channel>
  <items>
      <items>
        <pen>...</pen>
        <pencil>...</pencil>
        <paper>...</paper>
      </items>
  </items>
</channel>