让孩子使用Lucene的TaxonomyReader

Question

In Lucene , I am using the TaxonomyReader to read an index of a taxonomy stored in my disk. For a given category, I need to find all categories that are its children. However, in the Lucene's API I could find a method to retrieve the parent but not with the children. There is a method called getChildrenArrays() that returns a ChildrenArrays object. As you can see, this class only has two methods:

• getYoungestChildArray
• getOlderSiblingArray

I want to implement Enumerator using these two methods. Does someone know how to do it?

Answer 1

I got the following:

private class EnumChildren implements Enumeration<Integer> {
    int category, current;
    int[] next, first;

    public EnumChildren(int category) {
        ChildrenArrays childrenArrays = tr.getChildrenArrays();
        first = childrenArrays.getYoungestChildArray(); 
        next = childrenArrays.getOlderSiblingArray();
        current = first[category];
    }

    public boolean hasChildren() {
        return (current != TaxonomyReader.INVALID_ORDINAL);
    }

    @Override
    public boolean hasMoreElements() {  
        current = next[current];
        return (current != TaxonomyReader.INVALID_ORDINAL);
    }

    @Override
    public Integer nextElement() {
        return current;
    }
}

Ans is used as:

ordinal = tr.getOrdinal(new CategoryPath(nodeCategory.getPath(), '/')); 
        EnumChildren childrenEnumeration = new EnumChildren(ordinal);
        if (childrenEnumeration.hasChildren()) {
            do {
                int current = childrenEnumeration.nextElement();
                Category child = new Category(tr.getPath(current).toString());
                addChildren(child);
                nodeCategory.children.add(child);
            } while (childrenEnumeration.hasMoreElements());
        }