NamespaceContextImpl.java

/*
 * aitools utilities
 * Copyright (C) 2006 Noel Bush
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.

 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

package org.aitools.util.xml;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import javax.xml.XMLConstants;
import javax.xml.namespace.NamespaceContext;

/**
 * A minimal, basic implementation of this interface.
 * 
 * @author <a href="mailto:noel@aitools.org">Noel Bush</a>
 */
public class NamespaceContextImpl implements NamespaceContext {

  private Map<String, List<String>> uriToPrefix = new HashMap<String, List<String>>();

  private Map<String, String> prefixToURI = new HashMap<String, String>();

  /**
   * Associates the given namespace URI with the given prefix. If the prefix is already associated with another
   * namespace URI, an exception is thrown.
   * 
   * @param namespaceURI
   * @param prefix
   * @throws IllegalArgumentException if the prefix is already associated with another namespace URI
   */
  public void add(String namespaceURI, String prefix) {
    if (this.prefixToURI.containsKey(prefix)) {
      throw new IllegalArgumentException(String.format(
          "Prefix \"%s\" is already associated with namespace URI \"%s\".", prefix, this.prefixToURI.get(prefix)));
    }
    List<String> prefixes;
    if (this.uriToPrefix.containsKey(namespaceURI)) {
      prefixes = this.uriToPrefix.get(namespaceURI);
    }
    else {
      prefixes = new ArrayList<String>();
      this.uriToPrefix.put(namespaceURI, prefixes);
    }
    prefixes.add(prefix);
    this.prefixToURI.put(prefix, namespaceURI);
  }

  /**
   * @see javax.xml.namespace.NamespaceContext#getNamespaceURI(java.lang.String)
   */
  @Override
  public String getNamespaceURI(String prefix) {
    if (prefix == null) {
      throw new IllegalArgumentException("Prefix cannot be null.");
    }
    if (prefix.equals(XMLConstants.DEFAULT_NS_PREFIX)) {
      return XMLConstants.NULL_NS_URI;
    }
    if (!this.prefixToURI.containsKey(prefix)) {
      return XMLConstants.NULL_NS_URI;
    }
    if (prefix.equals(XMLConstants.XML_NS_PREFIX)) {
      return XMLConstants.XML_NS_URI;
    }
    if (prefix.equals(XMLConstants.XMLNS_ATTRIBUTE)) {
      return XMLConstants.XMLNS_ATTRIBUTE_NS_URI;
    }
    return this.prefixToURI.get(prefix);
  }

  /**
   * @see javax.xml.namespace.NamespaceContext#getPrefix(java.lang.String)
   */
  @Override
  public String getPrefix(String namespaceURI) {
    if (namespaceURI == null) {
      throw new IllegalArgumentException("Namespace URI cannot be null.");
    }
    if (namespaceURI.equals(XMLConstants.NULL_NS_URI)) {
      return XMLConstants.DEFAULT_NS_PREFIX;
    }
    if (namespaceURI.equals(XMLConstants.XML_NS_URI)) {
      return XMLConstants.XML_NS_PREFIX;
    }
    if (namespaceURI.equals(XMLConstants.XMLNS_ATTRIBUTE_NS_URI)) {
      return XMLConstants.XMLNS_ATTRIBUTE;
    }
    if (!this.uriToPrefix.containsKey(namespaceURI)) {
      return null;
    }
    return this.uriToPrefix.get(namespaceURI).get(0);
  }

  /**
   * @see javax.xml.namespace.NamespaceContext#getPrefixes(java.lang.String)
   */
  @Override
  public Iterator<String> getPrefixes(String namespaceURI) {
    if (namespaceURI == null) {
      throw new IllegalArgumentException("Namespace URI cannot be null.");
    }
    if (namespaceURI.equals(XMLConstants.NULL_NS_URI)) {
      List<String> result = new ArrayList<String>(1);
      result.add(XMLConstants.DEFAULT_NS_PREFIX);
      return Collections.unmodifiableList(result).iterator();
    }
    if (namespaceURI.equals(XMLConstants.XML_NS_URI)) {
      List<String> result = new ArrayList<String>(1);
      result.add(XMLConstants.XML_NS_PREFIX);
      return Collections.unmodifiableList(result).iterator();
    }
    if (namespaceURI.equals(XMLConstants.XMLNS_ATTRIBUTE_NS_URI)) {
      List<String> result = new ArrayList<String>(1);
      result.add(XMLConstants.XMLNS_ATTRIBUTE);
      return Collections.unmodifiableList(result).iterator();
    }
    if (!this.uriToPrefix.containsKey(namespaceURI)) {
      List<String> result = new ArrayList<String>(0);
      return Collections.unmodifiableList(result).iterator();
    }
    return Collections.unmodifiableList(this.uriToPrefix.get(namespaceURI)).iterator();
  }
}