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Java 使用ServiceLoader加载服务类

欢马劈雪

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使用ServiceLoader加载服务类

实例源码：

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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);

}

* 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.

*
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编辑于 2020-03-26 09:23:272020-03-26 09:23:27

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