Sitemap interface and classes for DD4T 2 Java

Sitemap.java

public interface Sitemap {
    //Always one root Folder
    Folder getFolder();
    void setFolder(Folder folder);
    
    //Example
    List<BaseItem> getTopNavigation();
}

@JsonIgnoreProperties(ignoreUnknown = true)
public abstract class BaseSitemap implements Sitemap {
    private Folder folder;

    @Override
    public Folder getFolder() {
        return folder;
    }

    @Override
    public void setFolder(Folder folder) {
        this.folder = folder;
    }
}

public class SitemapImpl extends BaseSitemap {

    @Override
    public List<BaseItem> getTopNavigation()
    {
        List<BaseItem> topNavigationItems = getTopItemsRecursive(this.getFolder(), new ArrayList<>());
        return topNavigationItems;
    }

    //TODO: Method to be refined
    private <T extends BaseItem> List<BaseItem> getTopItemsRecursive(T currentItem, List<BaseItem> allItems)
    {
        if(null == allItems)
            allItems = new ArrayList<>();

        if(currentItem.isTopnav())
            allItems.add(currentItem);

        if(currentItem.getClass().equals(Folder.class))
        {
            Folder folder = (Folder) currentItem;

            for(Folder subFolder : folder.getFolders()) {
                getTopItemsRecursive(subFolder, allItems);
            }

            for(Page page : folder.getPages()) {
                getTopItemsRecursive(page, allItems);
            }
        }
        return allItems;
    }
}

public abstract class BaseItem {

    private String id;
    private String title;
    private boolean topnav;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public boolean isTopnav() {
        return topnav;
    }

    public void setTopnav(boolean topnav) {
        this.topnav = topnav;
    }
}

public class Folder extends BaseItem {
    private int level;
    private ArrayList<Folder> folders;
    private ArrayList<Page> pages;

    public int getLevel() {
        return level;
    }

    public void setLevel(int level) {
        this.level = level;
    }

    public ArrayList<Page> getPages() {
        if (null==pages) {
            return new ArrayList<>();
        }
        return pages;
    }

    public void setPages(ArrayList<Page> pages) {
        this.pages = pages;
    }

    public ArrayList<Folder> getFolders() {
        if (null==folders) {
            return new ArrayList<>();
        }
        return folders;
    }

    public void setFolders(ArrayList<Folder> folders) {
        this.folders = folders;
    }
}

public class Page extends BaseItem {
    @JsonProperty("default")
    private boolean isDefault;

    public boolean isDefault() {
        return isDefault;
    }

    public void setDefault(boolean aDefault) {
        isDefault = aDefault;
    }
}