Load service class with ServiceLoader - Java Object Oriented Design

Java examples for Object Oriented Design:interface

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Description

Load service class with ServiceLoader

Demo Code

import java.util.Iterator;
import java.util.ServiceConfigurationError;
import java.util.ServiceLoader;
import java.util.SortedMap;
import java.util.TreeMap;

public class DictionaryDemo {

    public static void main(String[] args) {

        DictionaryService dictionary = DictionaryService.getInstance();
        System.out.println(DictionaryDemo.lookup(dictionary, "book"));
        System.out.println(DictionaryDemo.lookup(dictionary, "editor"));
        System.out.println(DictionaryDemo.lookup(dictionary, "xml"));
        System.out.println(DictionaryDemo.lookup(dictionary, "REST"));
    }/*  w  ww.  j a  v  a 2  s  . c o m*/

    public static String lookup(DictionaryService dictionary, String word) {
        String outputString = word + ": ";
        String definition = dictionary.getDefinition(word);
        if (definition == null) {
            return outputString + "Cannot find definition for this word.";
        } else {
            return outputString + definition;
        }
    }
}


class DictionaryService {

    private static DictionaryService service;
    private ServiceLoader<Dictionary> loader;

    private DictionaryService() {
        loader = ServiceLoader.load(Dictionary.class);
    }

    public static synchronized DictionaryService getInstance() {
        if (service == null) {
            service = new DictionaryService();
        }
        return service;
    }

    public String getDefinition(String word) {
        String definition = null;

        try {
            Iterator<Dictionary> dictionaries = loader.iterator();
            while (definition == null && dictionaries.hasNext()) {
                Dictionary d = dictionaries.next();
                definition = d.getDefinition(word);
            }
        } catch (ServiceConfigurationError serviceError) {
            definition = null;
            serviceError.printStackTrace();

        }
        return definition;
    }
}

interface Dictionary {
    public String getDefinition(String word);
}

/**
 *
 * @author John O'Conner
 */
class ExtendedDictionary implements Dictionary {

    private SortedMap<String, String> map;

    /**
     * Creates a new instance of ExtendedDictionary
     */
    public ExtendedDictionary() {
        map = new TreeMap<String, String>();
        map.put("xml",
                "a document standard often used in web services, among other "
                        + "things");
        map.put("REST",
                "an architecture style for creating, reading, updating, "
                        + "and deleting data that attempts to use the common "
                        + "vocabulary of the HTTP protocol; Representational State "
                        + "Transfer");
    }

    @Override
    public String getDefinition(String word) {
        return map.get(word);
    }

}


/**
 *
 * @author John O'Conner
 */
 class GeneralDictionary implements Dictionary {

    private SortedMap<String, String> map;

    /** Creates a new instance of GeneralDictionary */
    public GeneralDictionary() {
        map = new TreeMap<String, String>();
        map.put("book",
                "a set of written or printed pages, usually bound with "
                        + "a protective cover");
        map.put("editor", "a person who edits");
    }

    @Override
    public String getDefinition(String word) {
        return map.get(word);
    }

}

/*
 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Oracle or the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

Result


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