Java ServiceLoader類代碼示例

import java.util.ServiceLoader; //導入依賴的package包/類
public static ObjectMapper createObjectMapper() {
    final YAMLFactory yamlFactory = new YAMLFactory()
        .configure(YAMLGenerator.Feature.USE_NATIVE_TYPE_ID, false)
        .configure(YAMLGenerator.Feature.MINIMIZE_QUOTES, true)
        .configure(YAMLGenerator.Feature.ALWAYS_QUOTE_NUMBERS_AS_STRINGS, true)
        .configure(YAMLGenerator.Feature.USE_NATIVE_TYPE_ID, false);

    ObjectMapper mapper = new ObjectMapper(yamlFactory)
        .registerModule(new Jdk8Module())
        .setSerializationInclusion(JsonInclude.Include.NON_EMPTY)
        .enable(SerializationFeature.INDENT_OUTPUT)
        .disable(SerializationFeature.WRITE_NULL_MAP_VALUES);

    for (Step step : ServiceLoader.load(Step.class, YamlHelpers.class.getClassLoader())) {
        mapper.registerSubtypes(new NamedType(step.getClass(), step.getKind()));
    }

    return mapper;
}
 

import java.util.ServiceLoader; //導入依賴的package包/類
private static <T> T findServiceProvider(final Class<T> type)
        throws DatatypeConfigurationException
{
    try {
        return AccessController.doPrivileged(new PrivilegedAction<T>() {
            public T run() {
                final ServiceLoader<T> serviceLoader = ServiceLoader.load(type);
                final Iterator<T> iterator = serviceLoader.iterator();
                if (iterator.hasNext()) {
                    return iterator.next();
                } else {
                    return null;
                }
            }
        });
    } catch(ServiceConfigurationError e) {
        final DatatypeConfigurationException error =
                new DatatypeConfigurationException(
                    "Provider for " + type + " cannot be found", e);
        throw error;
    }
}
 

import java.util.ServiceLoader; //導入依賴的package包/類
private static AsynchronousChannelProvider loadProviderAsService() {
    ServiceLoader<AsynchronousChannelProvider> sl =
        ServiceLoader.load(AsynchronousChannelProvider.class,
                           ClassLoader.getSystemClassLoader());
    Iterator<AsynchronousChannelProvider> i = sl.iterator();
    for (;;) {
        try {
            return (i.hasNext()) ? i.next() : null;
        } catch (ServiceConfigurationError sce) {
            if (sce.getCause() instanceof SecurityException) {
                // Ignore the security exception, try the next provider
                continue;
            }
            throw sce;
        }
    }
}
 

import java.util.ServiceLoader; //導入依賴的package包/類
private static Map<String, HandlerBuilder> loadBuilders(final ClassLoader classLoader) {
    ServiceLoader<HandlerBuilder> loader = ServiceLoader.load(HandlerBuilder.class, classLoader);
    final Map<String, HandlerBuilder> ret = new HashMap<>();
    for (HandlerBuilder builder : loader) {
        if (ret.containsKey(builder.name())) {
            if (ret.get(builder.name()).getClass() != builder.getClass()) {
                throw UndertowMessages.MESSAGES.moreThanOneHandlerWithName(builder.name(), builder.getClass(), ret.get(builder.name()).getClass());
            }
        } else {
            ret.put(builder.name(), builder);
        }
    }
    return ret;
}
 

import java.util.ServiceLoader; //導入依賴的package包/類
/**
 * Load {@link BeanPropertyPostProcessor}s from <code>META-INF/services</code> extensions.
 * @param classLoader ClassLoader to use
 * @return {@link BeanPropertyPostProcessor}s list, empty if none found
 */
private void init(final ClassLoader classLoader) {
	LOGGER.debug(() -> "Load BeanPropertyPostProcessors for classloader [" + classLoader
			+ "] using ServiceLoader with service name: " + BeanPropertyPostProcessor.class.getName());
	Iterable<BeanPropertyPostProcessor> postProcessors = AccessController
			.doPrivileged(new PrivilegedAction<Iterable<BeanPropertyPostProcessor>>() {
				@Override
				public Iterable<BeanPropertyPostProcessor> run() {
					return ServiceLoader.load(BeanPropertyPostProcessor.class, classLoader);
				}
			});
	postProcessors.forEach(pr -> {
		propertyPostProcessors.add(pr);
		LOGGER.debug(() -> "Loaded and registered BeanPropertyPostProcessor [" + pr + "] for classloader ["
				+ classLoader + "]");
	});
	// sort by priority
	Collections.sort(propertyPostProcessors, PRIORITY_COMPARATOR);
}
 

import java.util.ServiceLoader; //導入依賴的package包/類
@Test
public void validateServiceIsLocatableViaServiceLoader() {
    ServiceLoader<Processor> loader = ServiceLoader.<Processor> load(Processor.class);
    Iterator<Processor> iter = loader.iterator();
    boolean pubJmsPresent = false;
    boolean consumeJmsPresent = false;
    while (iter.hasNext()) {
        Processor p = iter.next();
        if (p.getClass().getSimpleName().equals(PublishJMS.class.getSimpleName())) {
            pubJmsPresent = true;
        } else if (p.getClass().getSimpleName().equals(ConsumeJMS.class.getSimpleName())) {
            consumeJmsPresent = true;
        }

    }
    assertTrue(pubJmsPresent);
    assertTrue(consumeJmsPresent);
}
 

import java.util.ServiceLoader; //導入依賴的package包/類
public static void main(String[] args) {
    ServiceLoader<Analysis> analyses = ServiceLoader.load(Analysis.class);
  //  analyses.stream().map(ServiceLoader.Provider::get).forEach(analyzer -> System.out.println(analyzer.getName()));
    Set<Analysis> collect = analyses.stream()
                                    .filter(p -> isAnno(p.type()))
                                    .map(ServiceLoader.Provider::get).collect(Collectors.toSet());

    Person nao = new Person(0, 0);
    Person miniperson = new Person(10, 0);
    Person minperson = new Person(1001, 0);
    Person minxperson = new Person(1001, 11);
    Person maxperson = new Person(100000, 11);
    Person maxxperson = new Person(100000, 26);
    Person poorperson = new Person(100000, 0);

    collect.forEach(p->System.out.println(p.analyze(maxxperson)));


}
 

import java.util.ServiceLoader; //導入依賴的package包/類
/**
 * コンストラクタ
 *
 * @param connectionSupplier コネクションサプライヤ
 * @param loadPath SQLファイルの読み込みルートパス
 */
private DefaultSqlConfig(final ConnectionSupplier connectionSupplier, final String loadPath) {
	super();
	this.connectionSupplier = connectionSupplier;

	this.sqlManager = new SqlManagerImpl(loadPath);
	this.sqlFilterManager = new SqlFilterManagerImpl();
	this.sqlContextFactory = new SqlContextFactoryImpl();
	this.entityHandler = new DefaultEntityHandler();

	this.dialect = StreamSupport.stream(ServiceLoader.load(Dialect.class).spliterator(), false).filter(d -> d.accept(connectionSupplier)).findFirst().orElseGet(DefaultDialect::new);

	this.sqlAgentFactory = new SqlAgentFactoryImpl(this);

	initialize();
}
 

import java.util.ServiceLoader; //導入依賴的package包/類
/**
 * Looks for all "META-INF/services/[className]" files and
 * create one instance for each class name found inside this file.
 */
private <T> List<T> findServices(Class<T> clazz) {
    final List<T> result = new ArrayList<>();
    final boolean debug = getDebugPropertyValue();
    try {
        // TCCL allows user plugins to be loaded even if xjc is in jdk
        // We have to use our SecureLoader to obtain it because we are trying to avoid SecurityException
        final ClassLoader tccl = SecureLoader.getContextClassLoader();
        final ServiceLoader<T> sl = ServiceLoader.load(clazz, tccl);
        for (T t : sl)
            result.add(t);
    } catch (Throwable e) {
        // ignore any error
        StringWriter w = new StringWriter();
        e.printStackTrace(new PrintWriter(w));
        pluginLoadFailure = w.toString();
        if (debug)
            System.out.println(pluginLoadFailure);
    }
    return result;
}
 

import java.util.ServiceLoader; //導入依賴的package包/類
@BeforeClass(alwaysRun=true)
public static void loadTokenParser() throws Exception {
    System.out.printf("TokenValidationTest.initClass\n");
    publicKey = TokenUtils.readPublicKey("/publicKey.pem");
    if(publicKey == null) {
        throw new IllegalStateException("Failed to load /publicKey.pem resource");
    }

    // Load the ITokenParser via the ServiceLoader
    ServiceLoader<ITokenParser> serviceLoader = ServiceLoader.load(ITokenParser.class);
    if(serviceLoader.iterator().hasNext() == false) {
        // Try to obtain ITokenParser via CDI
        tokenParser = CDI.current().select(ITokenParser.class).get();
        if(tokenParser == null) {
            throw new IllegalStateException(String.format("An %s service provider or producer is required", ITokenParser.class.getName()));
        }
    }
    else {
        tokenParser = serviceLoader.iterator().next();
        if (tokenParser == null) {
            throw new IllegalStateException(String.format("Service provider for %s  produced a null parser", ITokenParser.class.getName()));
        }
    }
    System.out.printf("Using ITokenParser: %s\n", tokenParser);
}
 

import java.util.ServiceLoader; //導入依賴的package包/類
/**
 * Basic test of ServiceLoader.load, using the class loader for
 * a module in a custom layer as the context.
 */
@Test
public void testWithCustomLayer1() {
    ModuleLayer layer = createCustomLayer("bananascript");

    ClassLoader loader = layer.findLoader("bananascript");
    List<ScriptEngineFactory> providers
        = collectAll(ServiceLoader.load(ScriptEngineFactory.class, loader));

    // should have at least 2 x bananascript + pearscript
    assertTrue(providers.size() >= 3);

    // first element should be the provider in the custom layer
    ScriptEngineFactory factory = providers.get(0);
    assertTrue(factory.getClass().getClassLoader() == loader);
    assertTrue(factory.getClass().getModule().getLayer() == layer);
    assertTrue(factory.getEngineName().equals("BananaScriptEngine"));

    // remainder should be the boot layer
    providers.remove(0);
    Set<String> names = providers.stream()
            .map(ScriptEngineFactory::getEngineName)
            .collect(Collectors.toSet());
    assertTrue(names.contains("BananaScriptEngine"));
    assertTrue(names.contains("PearScriptEngine"));
}
 

import java.util.ServiceLoader; //導入依賴的package包/類
@Override
public LoggingBackend run() {
    final Iterator<LoggerFinder> iterator =
        ServiceLoader.load(LoggerFinder.class, ClassLoader.getSystemClassLoader())
        .iterator();
    if (iterator.hasNext()) {
        return LoggingBackend.CUSTOM; // Custom Logger Provider is registered
    }
    // No custom logger provider: we will be using the default
    // backend.
    final Iterator<DefaultLoggerFinder> iterator2 =
        ServiceLoader.loadInstalled(DefaultLoggerFinder.class)
        .iterator();
    if (iterator2.hasNext()) {
        // LoggingProviderImpl is registered. The default
        // implementation is java.util.logging
        String cname = System.getProperty("java.util.logging.config.class");
        String fname = System.getProperty("java.util.logging.config.file");
        return (cname != null || fname != null)
            ? LoggingBackend.JUL_WITH_CONFIG
            : LoggingBackend.JUL_DEFAULT;
    } else {
        // SimpleConsoleLogger is used
        return LoggingBackend.NONE;
    }
}
 

import java.util.ServiceLoader; //導入依賴的package包/類
/**
 * The plugins accessible in the current context.
 *
 * @param pluginsLayer
 * @return The list of plugins.
 */
private static <T extends Plugin> List<T> getPlugins(Class<T> clazz, ModuleLayer pluginsLayer) {
    Objects.requireNonNull(pluginsLayer);
    List<T> factories = new ArrayList<>();
    try {
        Iterator<T> providers
                = ServiceLoader.load(pluginsLayer, clazz).iterator();
        while (providers.hasNext()) {
            factories.add(providers.next());
        }
        registeredPlugins.values().stream().forEach((fact) -> {
            if (clazz.isInstance(fact)) {
                @SuppressWarnings("unchecked")
                T trans = (T) fact;
                factories.add(trans);
            }
        });
        return factories;
    } catch (Exception ex) {
        throw new PluginException(ex);
    }
}
 

import java.util.ServiceLoader; //導入依賴的package包/類
private void registerInstalledProviders() {
    /*
      We need to load installed providers from the
      system classpath (typically the <code>lib/ext</code>
      directory in in the Java installation directory)
      in the privileged mode in order to
      be able read corresponding jar files even if
      file read capability is restricted (like the
      applet context case).
     */
    PrivilegedAction doRegistration =
        new PrivilegedAction() {
            public Object run() {
                Iterator categories = getCategories();
                while (categories.hasNext()) {
                    Class<IIOServiceProvider> c = (Class)categories.next();
                    for (IIOServiceProvider p : ServiceLoader.loadInstalled(c)) {
                        registerServiceProvider(p);
                    }
                }
                return this;
            }
        };

    AccessController.doPrivileged(doRegistration);
}
 

import java.util.ServiceLoader; //導入依賴的package包/類
/**
 * Basic test of stream() to ensure that elements for providers in named
 * modules come before elements for providers in unnamed modules.
 */
@Test
public void testStreamOrder() {
    List<Class<?>> types = ServiceLoader.load(ScriptEngineFactory.class)
            .stream()
            .map(Provider::type)
            .collect(Collectors.toList());

    boolean foundUnnamed = false;
    for (Class<?> factoryClass : types) {
        if (factoryClass.getModule().isNamed()) {
            if (foundUnnamed) {
                assertTrue(false, "Named module element after unnamed");
            }
        } else {
            foundUnnamed = true;
        }
    }
}