XPathNamespaceContext.java

/**************************************************************************************
 * Copyright (C) 2008 EsperTech, Inc. All rights reserved.                            *
 * http://esper.codehaus.org                                                          *
 * http://www.espertech.com                                                           *
 * ---------------------------------------------------------------------------------- *
 * The software in this package is published under the terms of the GPL license       *
 * a copy of which has been included with this distribution in the license.txt file.  *
 **************************************************************************************/
package com.espertech.esper.event.xml;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

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

/**
 * Provides the namespace context information for compiling XPath expressions.
 */
public class XPathNamespaceContext implements NamespaceContext {

	//namespace to prefix
	private Map<String,String> namespaces;

	//prefix to namespace
	private Map<String,String> prefix;

	private String defaultNamespace;

    /**
     * Ctor.
     */
    public XPathNamespaceContext() {
		super();
		namespaces = new HashMap<String,String>();
		prefix = new HashMap<String,String>();
	}

	public String getNamespaceURI(String prefix) {
		if (prefix == null) {
			throw new IllegalArgumentException("prefix can't be null");
        }
        if (prefix.equals(XMLConstants.DEFAULT_NS_PREFIX)) {
			return defaultNamespace;
        }
        if (prefix.equals(XMLConstants.XML_NS_PREFIX)) {
			return XMLConstants.XML_NS_URI;
        }
        if (prefix.equals(XMLConstants.XMLNS_ATTRIBUTE)) {
			return XMLConstants.XMLNS_ATTRIBUTE_NS_URI;
        }

        String namespace = namespaces.get(prefix);
		if (namespace == null)
			return XMLConstants.NULL_NS_URI;

		return namespace;
	}

	public String getPrefix(String namespaceURI) {
        if (namespaceURI == null)
        {
            return null;
        }
        if (defaultNamespace != null) {
            if (namespaceURI.equals(defaultNamespace)) {
                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;
        }
		return prefix.get(namespaceURI);
	}

	public Iterator getPrefixes(String namespaceURI) {
		throw new RuntimeException("Not Implemented");
	}

    /**
     * Sets the default namespace.
     * @param defaultNamespace is the default namespace
     */
    public void setDefaultNamespace(String defaultNamespace) {
		this.defaultNamespace = defaultNamespace;
	}

    /**
     * Add a namespace prefix and namespace name to context.
     * @param prefix  - namespace prefix
     * @param uri - namespace name to add
     */
    public void addPrefix(String prefix,String uri) {
		namespaces.put(prefix,uri);
		this.prefix.put(uri,prefix);
	}

    public String toString()
    {
        StringBuilder builder = new StringBuilder("XPathNamespaceContext default namespace '" + defaultNamespace + "' maps {");
        String delimiter = "";
        for (Map.Entry<String, String> entry : prefix.entrySet())
        {
            builder.append(delimiter);
            builder.append(entry.getKey());
            builder.append("=");
            builder.append(entry.getValue());
            delimiter = ",";
        }
        builder.append("}");
        return builder.toString();
    }
}