QName.java

/*
    Priha - A JSR-170 implementation library.

    Copyright (C) 2007-2009 Janne Jalkanen (Janne.Jalkanen@iki.fi)

    Licensed 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 
    
      http://www.apache.org/licenses/LICENSE-2.0 
      
    Unless required by applicable law or agreed to in writing, software 
    distributed under the License is distributed on an "AS IS" BASIS, 
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
    See the License for the specific language governing permissions and 
    limitations under the License. 
 */
package org.priha.util;

import java.io.Serializable;

import javax.xml.XMLConstants;

/**
 *  Reimplements {@link javax.xml.namespace.QName}, because it prevents subclassing
 *  by declaring equals() as final.
 *  <p>
 *  QNames are immutable, i.e. once they are created, they cannot be changed.
 */
public class QName implements Serializable, Comparable<QName>
{
    private String m_uri;
    private String m_localName;
    private String m_prefix;
    
    private transient String m_cachedString;
    
    private static final long serialVersionUID = 1L;
    
    public QName( String uri, String name, String prefix )
    {
        m_uri = (uri != null) ? uri.intern() : XMLConstants.NULL_NS_URI;
        
        if( name.indexOf( '[' ) != -1 ) throw new IllegalArgumentException("Must not have '['");
        m_localName = name.intern();
        m_prefix = prefix;
    }

    public QName( String localName )
    {
        this( null, localName, XMLConstants.DEFAULT_NS_PREFIX );
    }

    public QName( String namespaceURI, String localpart )
    {
        this( namespaceURI, localpart, XMLConstants.DEFAULT_NS_PREFIX );
    }

    public String getNamespaceURI()
    {
        return m_uri;
    }

    public String getLocalPart()
    {
        return m_localName;
    }

    public String getPrefix()
    {
        return m_prefix;
    }

    public static QName valueOf( String val )
    {
        if( val == null ) throw new IllegalArgumentException("Null value given to QName.valueOf()");
        
        if( val.length() == 0 ) return new QName(val);
        
        if( val.charAt(0) == '{' )
        {
            int end = val.indexOf( '}' );
            if( end == -1 ) throw new IllegalArgumentException("Missing }: "+val);
            
            return new QName( val.substring( 1,end ), 
                              val.substring( end+1 ), 
                              XMLConstants.DEFAULT_NS_PREFIX );
        }
        
        return new QName(val);
    }
    
    public boolean equals( Object o )
    {
        if( o == this ) return true;
        
        if( o != null && o instanceof QName )
        {
            QName q = (QName) o;
            return q.m_localName.equals(m_localName) && q.m_uri.equals( m_uri );
        }
        
        return false;
    }
    
    public int hashCode()
    {
        return getLocalPart().hashCode() ^ getNamespaceURI().hashCode();
    }
    
    public String toString()
    {
        if( m_cachedString == null )
        {
            if( m_uri.equals( XMLConstants.NULL_NS_URI ) ) 
                m_cachedString = m_localName;
            else
                m_cachedString = "{"+m_uri+"}"+m_localName;
        }
        return m_cachedString;
    }
    
    public int compareTo( QName o )
    {
        int res = m_uri.compareTo( o.m_uri );
        
        if( res == 0 )
            res = m_localName.compareTo( o.m_localName );
        
        return res;
    }   
}