AttFilter.java

package org.jdom2.contrib.dtdaware;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import org.jdom2.Attribute;
import org.jdom2.Element;
import org.jdom2.filter.AbstractFilter;


/**
 * This AttFilter can be programmed to ignore specific attributes.
 * The ignore criteria is based on the Attribute name, value, and the
 * Element it is attached to.
 * 
 * @author Rolf Lear
 *
 */
public class AttFilter extends AbstractFilter<Attribute> {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	/**
	 * Yeah, this is complicated, but it is basically a search tree index.
	 * This is a nested index of attribute details:
	 * <p>
	 * <ol>
	 * <li> at the top is the attribute name
	 * <li> then the Attribute value.
	 * <li> next is the Element name. We only check this level if the attribute
	 *      name and value matches to something that is ignored.
	 * <li> next we check to make sure that we are in the correct Attribute Namespace
	 * <li> then finally the Element namespace.
	 * </ol>
	 * <p>
	 * If we search this index tree and all the details match existing entries,
	 * then it is an ignored attribute. The order is set up in such a way that
	 * there should not need to be many checks in HashMaps for non-ignored
	 * content... essentiually we have to have the same attname and attvalue
	 * before the system even checks the Attribute's parent details.
	 */
	//            attname    attval     emtname    attns      emtns
	private final Map<String,Map<String,Map<String,Map<String,Set<String>>>>>
		ignores = new HashMap<String,Map<String,Map<String,Map<String,Set<String>>>>>();

	/**
	 * Ignore an attribute (where the attribute and element are both in the 
	 * no-uri namespace).
	 * @param elementname The name of the Attribute's parent element.
	 * @param attname The name of the attribute.
	 * @param attvalue The attribute value to ignore.
	 */
	public void ignore(String elementname, String attname, String attvalue) {
		ignore("", elementname, "", attname, attvalue);
	}
	
	/**
	 * Ignore an attribute.
	 * @param elementuri The NamespaceURI of the Attribute's parent Element
	 * @param elementname The name of the Attribute's parent Element.
	 * @param atturi The Attribute's namespace URI.
	 * @param attname The name of the attribute.
	 * @param attvalue The attribute value.
	 */
	public void ignore(String elementuri, String elementname, 
			String atturi, String attname, String attvalue) {
		Map<String, Map<String, Map<String, Set<String>>>> av = 
				ignores.get(attname);
		if (av == null) {
			av = new HashMap<String, Map<String,Map<String,Set<String>>>>();
			ignores.put(attname, av);
		}
		Map<String, Map<String,Set<String>>> en = av.get(attvalue);
		if (en == null) {
			en = new HashMap<String, Map<String,Set<String>>>();
			av.put(attvalue, en);
		}
		Map<String, Set<String>> ans = en.get(elementname);
		if (ans == null) {
			ans = new HashMap<String, Set<String>>();
			en.put(elementname, ans);
		}
		Set<String> ens = ans.get(atturi);
		if (ens == null) {
			ens = new HashSet<String>();
			ans.put(atturi, ens);
		}
		ens.add(elementuri);
	}
	
	
	
	
	@Override
	public Attribute filter(Object content) {
		if (!(content instanceof Attribute)) {
			return null;
		}
		Attribute attribute = (Attribute)content;
		if (!ignores.isEmpty()) {
			// yes, there are ignores.
			final Map<String, Map<String, Map<String, Set<String>>>> av =
					ignores.get(attribute.getName());
			if (av != null) {
				// we are ignoring at least one attribute with this name.
				final Map<String, Map<String, Set<String>>> en = 
						av.get(attribute.getValue());
				if (en != null) {
					// we ignore something with the attribute name and value
					final Element e = attribute.getParent();
					final Map<String, Set<String>> ans = 
							en.get(e.getName());
					if (ans != null) {
						// and the same Element name
						final Set<String> ens = ans.get(attribute.getNamespaceURI());
						if (ens != null && ens.contains(e.getNamespaceURI())) {
							// and the same Attribute and Element namespace....
							// we match the ignored content...
							// skip this attribute.
							return null;
						}
					}
				}
			}
		}
		return attribute;
	}
	
	

}