Java 使用ServiceLoader加载服务类

​

import java.util.Iterator;

​

import java.util.ServiceConfigurationError;

​

import java.util.ServiceLoader;//来自 N  o w  J a v a . c o m

​

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"));

​

    }

​

​

    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.";//来 自 nowjava.com - 时代Java

​

        } 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.

​

 *

/**代码未完, 请加载全部代码(NowJava.com).**/