SpellCheckServiceImpl.java

/*
 *   Copyright 2006 The Apache Software Foundation
 *
 *   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.apache.felix.examples.spellcheckbinder;


import java.util.ArrayList;
import java.util.StringTokenizer;

import org.apache.felix.examples.dictionaryservice.DictionaryService;
import org.apache.felix.examples.spellcheckservice.SpellCheckService;


/**
 * This class re-implements the spell check service of Example 5. This service
 * implementation behaves exactly like the one in Example 5, specifically, it
 * aggregates all available dictionary services, monitors their dynamic
 * availability, and only offers the spell check service if there are dictionary
 * services available. The service implementation is greatly simplified, though,
 * by using the Service Binder. Notice that there is no OSGi references in the
 * application code; intead, the metadata.xml file describes the service
 * dependencies to the Service Binder, which automatically manages them and it
 * also automatically registers the spell check services as appropriate.
 * 
 * @author <a href="mailto:dev@felix.apache.org">Felix Project Team</a>
 */
public class SpellCheckServiceImpl implements SpellCheckService
{
    // List of service objects.
    private ArrayList m_svcObjList = new ArrayList();


    /**
     * This method is used by the Service Binder to add new dictionaries to the
     * spell check service.
     * 
     * @param dictionary
     *            the dictionary to add to the spell check service.
     */
    public void addDictionary( DictionaryService dictionary )
    {
        // Lock list and add service object.
        synchronized ( m_svcObjList )
        {
            m_svcObjList.add( dictionary );
        }
    }


    /**
     * This method is used by the Service Binder to remove dictionaries from the
     * spell check service.
     * 
     * @param dictionary
     *            the dictionary to remove from the spell check service.
     */
    public void removeDictionary( DictionaryService dictionary )
    {
        // Lock list and remove service object.
        synchronized ( m_svcObjList )
        {
            m_svcObjList.remove( dictionary );
        }
    }


    /**
     * Checks a given passage for spelling errors. A passage is any number of
     * words separated by a space and any of the following punctuation marks:
     * comma (,), period (.), exclamation mark (!), question mark (?),
     * semi-colon (;), and colon(:).
     * 
     * @param passage
     *            the passage to spell check.
     * @return An array of misspelled words or null if no words are misspelled.
     */
    public String[] check( String passage )
    {
        // No misspelled words for an empty string.
        if ( ( passage == null ) || ( passage.length() == 0 ) )
        {
            return null;
        }

        ArrayList errorList = new ArrayList();

        // Tokenize the passage using spaces and punctionation.
        StringTokenizer st = new StringTokenizer( passage, " ,.!?;:" );

        // Lock the service list.
        synchronized ( m_svcObjList )
        {
            // Loop through each word in the passage.
            while ( st.hasMoreTokens() )
            {
                String word = st.nextToken();
                boolean correct = false;

                // Check each available dictionary for the current word.
                for ( int i = 0; ( !correct ) && ( i < m_svcObjList.size() ); i++ )
                {
                    DictionaryService dictionary = ( DictionaryService ) m_svcObjList.get( i );

                    if ( dictionary.checkWord( word ) )
                    {
                        correct = true;
                    }
                }

                // If the word is not correct, then add it
                // to the incorrect word list.
                if ( !correct )
                {
                    errorList.add( word );
                }
            }
        }

        // Return null if no words are incorrect.
        if ( errorList.size() == 0 )
        {
            return null;
        }

        // Return the array of incorrect words.
        return ( String[] ) errorList.toArray( new String[errorList.size()] );
    }
}