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/* |
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* Copyright (C) 2016 AriaLyy(https://github.com/AriaLyy/Aria)
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* |
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* Licensed under the Apache License, Version 2.0 (the "License"); |
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* you may not use this file except in compliance with the License. |
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* You may obtain a copy of the License at |
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* |
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* http://www.apache.org/licenses/LICENSE-2.0
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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*/ |
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package com.arialyy.aria.util; |
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import java.io.BufferedReader; |
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import java.io.IOException; |
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import java.io.InputStream; |
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import java.io.InputStreamReader; |
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import java.net.URL; |
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import java.util.ArrayList; |
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import java.util.Enumeration; |
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import java.util.Iterator; |
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import java.util.List; |
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import java.util.ServiceConfigurationError; |
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import java.util.ServiceLoader; |
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/** |
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* aria 服务加载器 |
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* 参考{@link ServiceLoader} |
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*/ |
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public class AriaServiceLoader<S> { |
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private static final String PREFIX = "META-INF/services/"; |
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// The class or interface representing the service being loaded
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private final Class<S> service; |
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// The class loader used to locate, load, and instantiate providers
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private final ClassLoader loader; |
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// The access control context taken when the ServiceLoader is created
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// Android-changed: do not use legacy security code.
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// private final AccessControlContext acc;
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private LazyLoader lazyLoader; |
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public void reload() { |
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lazyLoader = new LazyLoader(service, loader); |
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} |
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private AriaServiceLoader(Class<S> svc, ClassLoader cl) { |
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service = svc; |
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loader = (cl == null) ? ClassLoader.getSystemClassLoader() : cl; |
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// Android-changed: Do not use legacy security code.
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// On Android, System.getSecurityManager() is always null.
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// acc = (System.getSecurityManager() != null) ? AccessController.getContext() : null;
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reload(); |
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} |
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public static <S> AriaServiceLoader<S> load(Class<S> service, ClassLoader loader) { |
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return new AriaServiceLoader<>(service, loader); |
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} |
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public static <S> AriaServiceLoader<S> load(Class<S> service) { |
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Thread.currentThread().setContextClassLoader(AriaServiceLoader.class.getClassLoader()); |
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ClassLoader cl = Thread.currentThread().getContextClassLoader(); |
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return AriaServiceLoader.load(service, cl); |
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} |
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public S getService(String serviceName) { |
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return lazyLoader.loadService(serviceName); |
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} |
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private class LazyLoader { |
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private Class<S> service; |
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private ClassLoader loader; |
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private Enumeration<URL> configs = null; |
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private Iterator<String> pending = null; |
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private LazyLoader(Class<S> service, ClassLoader loader) { |
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this.service = service; |
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this.loader = loader; |
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parseConfig(); |
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} |
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// Parse the content of the given URL as a provider-configuration file.
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//
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// @param service
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// The service type for which providers are being sought;
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// used to construct error detail strings
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//
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// @param u
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// The URL naming the configuration file to be parsed
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//
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// @return A (possibly empty) iterator that will yield the provider-class
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// names in the given configuration file that are not yet members
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// of the returned set
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//
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// @throws ServiceConfigurationError
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// If an I/O error occurs while reading from the given URL, or
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// if a configuration-file format error is detected
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//
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private Iterator<String> parse(Class<?> service, URL u) throws ServiceConfigurationError { |
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InputStream in = null; |
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BufferedReader r = null; |
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ArrayList<String> names = new ArrayList<>(); |
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try { |
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in = u.openStream(); |
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r = new BufferedReader(new InputStreamReader(in, "utf-8")); |
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int lc = 1; |
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while ((lc = parseLine(service, u, r, lc, names)) >= 0) ; |
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} catch (IOException x) { |
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fail(service, "Error reading configuration file", x); |
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} finally { |
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try { |
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if (r != null) r.close(); |
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if (in != null) in.close(); |
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} catch (IOException y) { |
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fail(service, "Error closing configuration file", y); |
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} |
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} |
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return names.iterator(); |
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} |
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private void fail(Class<?> service, String msg, Throwable cause) |
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throws ServiceConfigurationError { |
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throw new ServiceConfigurationError(service.getName() + ": " + msg, |
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cause); |
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} |
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private void fail(Class<?> service, String msg) |
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throws ServiceConfigurationError { |
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throw new ServiceConfigurationError(service.getName() + ": " + msg); |
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} |
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private void fail(Class<?> service, URL u, int line, String msg) |
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throws ServiceConfigurationError { |
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fail(service, u + ":" + line + ": " + msg); |
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} |
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// Parse a single line from the given configuration file, adding the name
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// on the line to the names list.
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//
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private int parseLine(Class<?> service, URL u, BufferedReader r, int lc, |
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List<String> names) |
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throws IOException, ServiceConfigurationError { |
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String ln = r.readLine(); |
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if (ln == null) { |
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return -1; |
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} |
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int ci = ln.indexOf('#'); |
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if (ci >= 0) ln = ln.substring(0, ci); |
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ln = ln.trim(); |
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int n = ln.length(); |
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if (n != 0) { |
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if ((ln.indexOf(' ') >= 0) || (ln.indexOf('\t') >= 0)) { |
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fail(service, u, lc, "Illegal configuration-file syntax"); |
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} |
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int cp = ln.codePointAt(0); |
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if (!Character.isJavaIdentifierStart(cp)) { |
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fail(service, u, lc, "Illegal provider-class name: " + ln); |
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} |
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for (int i = Character.charCount(cp); i < n; i += Character.charCount(cp)) { |
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cp = ln.codePointAt(i); |
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if (!Character.isJavaIdentifierPart(cp) && (cp != '.')) { |
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fail(service, u, lc, "Illegal provider-class name: " + ln); |
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} |
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} |
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if (!names.contains(ln)) { |
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names.add(ln); |
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} |
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} |
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return lc + 1; |
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} |
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private S loadService(String serviceName) { |
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while (pending.hasNext()) { |
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if (pending.next().equals(serviceName)) { |
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Class<?> c = null; |
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try { |
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c = Class.forName(serviceName, false, loader); |
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} catch (ClassNotFoundException x) { |
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fail(service, |
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// Android-changed: Let the ServiceConfigurationError have a cause.
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"Provider " + serviceName + " not found", x); |
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// "Provider " + cn + " not found");
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} |
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if (!service.isAssignableFrom(c)) { |
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// Android-changed: Let the ServiceConfigurationError have a cause.
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ClassCastException cce = new ClassCastException( |
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service.getCanonicalName() + " is not assignable from " + c.getCanonicalName()); |
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fail(service, |
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"Provider " + serviceName + " not a subtype", cce); |
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// fail(service,
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// "Provider " + cn + " not a subtype");
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} |
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try { |
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return service.cast(c.newInstance()); |
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} catch (Throwable x) { |
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fail(service, "Provider " + serviceName + " could not be instantiated", x); |
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} |
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} |
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} |
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throw new Error(); // This cannot happen
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} |
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/** |
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* 解析配置文件 |
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*/ |
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private void parseConfig() { |
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if (configs == null) { |
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try { |
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String fullName = PREFIX + service.getName(); |
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if (loader == null) { |
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configs = ClassLoader.getSystemResources(fullName); |
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} else { |
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configs = loader.getResources(fullName); |
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} |
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} catch (IOException x) { |
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fail(service, "Error locating configuration files", x); |
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} |
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} |
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while ((pending == null) || !pending.hasNext()) { |
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if (!configs.hasMoreElements()) { |
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return; |
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} |
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pending = parse(service, configs.nextElement()); |
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} |
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} |
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} |
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} |
laoyuyu
4 years ago