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 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 * Unless required by applicable law or agreed to in writing,
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 * under the License.
package org.apache.axiom.util.stax.dialect;

import java.util.Iterator;

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

 * Wrapper that fixes the behavior of {@link NamespaceContext#getNamespaceURI(String)}. The Javadoc
 * of that method clearly specifies that the return value of that method may never be
 * <code>null</code>. In particular, the expected result for an unbound prefix is
 * {@link XMLConstants#NULL_NS_URI}. However, many implementations incorrectly return
 * <code>null</code> in that case.
class NamespaceURICorrectingNamespaceContextWrapper implements NamespaceContext {
    private final NamespaceContext parent;
    public NamespaceURICorrectingNamespaceContextWrapper(NamespaceContext parent) {
        this.parent = parent;

    public String getNamespaceURI(String prefix) {
        String namespaceURI = parent.getNamespaceURI(prefix);
        return namespaceURI == null ? XMLConstants.NULL_NS_URI : namespaceURI;

    public String getPrefix(String namespaceURI) {
        return parent.getPrefix(namespaceURI);

    public Iterator getPrefixes(String namespaceURI) {
        return parent.getPrefixes(namespaceURI);