实验室网站建设,百度做一个网站怎么做呢,光明区建设局网站,android安卓版下载自定义classLoader实现加载外部jar, 以skywalking agent 类加载器为例子 整体思路
扩展findClass #xff0c;解决loadClass可以查找到扩展findResource#xff0c;解决getResources可以获取到资源
基本原理
ClassLoader loadClass的加载顺序 findLoadedClass 加载本地已经… 自定义classLoader实现加载外部jar, 以skywalking agent 类加载器为例子 整体思路
扩展findClass 解决loadClass可以查找到扩展findResource解决getResources可以获取到资源
基本原理
ClassLoader loadClass的加载顺序 findLoadedClass 加载本地已经加载过的class parent.loadClass 通过父类去加载class findClass 前面都没有加载到就通过findClass去搜索jar并加载class 扩展findClass
扩展findResource
扩展后AgentClassLoader.getDefault().getResources(“skywalking-plugin.def”); 就可以获取插件定义
完整源代码
AgentClassLoader
/** Licensed to the Apache Software Foundation (ASF) under one or more* contributor license agreements. See the NOTICE file distributed with* this work for additional information regarding copyright ownership.* The ASF licenses this file to You under the Apache License, Version 2.0* (the License); you may not use this file except in compliance with* the License. You may obtain a copy of the License at** http://www.apache.org/licenses/LICENSE-2.0** Unless required by applicable law or agreed to in writing, software* distributed under the License is distributed on an AS IS BASIS,* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.* See the License for the specific language governing permissions and* limitations under the License.**/package org.apache.skywalking.apm.agent.core.plugin.loader;import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.locks.ReentrantLock;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import lombok.RequiredArgsConstructor;
import org.apache.skywalking.apm.agent.core.boot.AgentPackageNotFoundException;
import org.apache.skywalking.apm.agent.core.boot.AgentPackagePath;
import org.apache.skywalking.apm.agent.core.boot.PluginConfig;
import org.apache.skywalking.apm.agent.core.conf.Config;
import org.apache.skywalking.apm.agent.core.conf.SnifferConfigInitializer;
import org.apache.skywalking.apm.agent.core.logging.api.ILog;
import org.apache.skywalking.apm.agent.core.logging.api.LogManager;
import org.apache.skywalking.apm.agent.core.plugin.PluginBootstrap;/*** The codeAgentClassLoader/code represents a classloader, which is in charge of finding plugins and interceptors.*/
public class AgentClassLoader extends ClassLoader {static {/** Try to solve the classloader dead lock. See https://github.com/apache/skywalking/pull/2016*/registerAsParallelCapable();}private static final ILog LOGGER LogManager.getLogger(AgentClassLoader.class);/*** The default class loader for the agent.*/private static AgentClassLoader DEFAULT_LOADER;private ListFile classpath;private ListJar allJars;private ReentrantLock jarScanLock new ReentrantLock();public static AgentClassLoader getDefault() {return DEFAULT_LOADER;}/*** Init the default class loader.** throws AgentPackageNotFoundException if agent package is not found.*/public static void initDefaultLoader() throws AgentPackageNotFoundException {if (DEFAULT_LOADER null) {synchronized (AgentClassLoader.class) {if (DEFAULT_LOADER null) {DEFAULT_LOADER new AgentClassLoader(PluginBootstrap.class.getClassLoader());}}}}public AgentClassLoader(ClassLoader parent) throws AgentPackageNotFoundException {super(parent);File agentDictionary AgentPackagePath.getPath();classpath new LinkedList();Config.Plugin.MOUNT.forEach(mountFolder - classpath.add(new File(agentDictionary, mountFolder)));}Overrideprotected Class? findClass(String name) throws ClassNotFoundException {ListJar allJars getAllJars();String path name.replace(., /).concat(.class);for (Jar jar : allJars) {JarEntry entry jar.jarFile.getJarEntry(path);if (entry null) {continue;}try {URL classFileUrl new URL(jar:file: jar.sourceFile.getAbsolutePath() !/ path);byte[] data;try (final BufferedInputStream is new BufferedInputStream(classFileUrl.openStream()); final ByteArrayOutputStream baos new ByteArrayOutputStream()) {int ch;while ((ch is.read()) ! -1) {baos.write(ch);}data baos.toByteArray();}return processLoadedClass(defineClass(name, data, 0, data.length));} catch (IOException e) {LOGGER.error(e, find class fail.);}}throw new ClassNotFoundException(Cant find name);}Overrideprotected URL findResource(String name) {ListJar allJars getAllJars();for (Jar jar : allJars) {JarEntry entry jar.jarFile.getJarEntry(name);if (entry ! null) {try {return new URL(jar:file: jar.sourceFile.getAbsolutePath() !/ name);} catch (MalformedURLException ignored) {}}}return null;}Overrideprotected EnumerationURL findResources(String name) throws IOException {ListURL allResources new LinkedList();ListJar allJars getAllJars();for (Jar jar : allJars) {JarEntry entry jar.jarFile.getJarEntry(name);if (entry ! null) {allResources.add(new URL(jar:file: jar.sourceFile.getAbsolutePath() !/ name));}}final IteratorURL iterator allResources.iterator();return new EnumerationURL() {Overridepublic boolean hasMoreElements() {return iterator.hasNext();}Overridepublic URL nextElement() {return iterator.next();}};}private Class? processLoadedClass(Class? loadedClass) {final PluginConfig pluginConfig loadedClass.getAnnotation(PluginConfig.class);if (pluginConfig ! null) {// Set up the plugin config when loaded by class loader at the first time.// Agent class loader just loaded limited classes in the plugin jar(s), so the cost of this// isAssignableFrom would be also very limited.SnifferConfigInitializer.initializeConfig(pluginConfig.root());}return loadedClass;}private ListJar getAllJars() {if (allJars null) {jarScanLock.lock();try {if (allJars null) {allJars doGetJars();}} finally {jarScanLock.unlock();}}return allJars;}private LinkedListJar doGetJars() {LinkedListJar jars new LinkedList();for (File path : classpath) {if (path.exists() path.isDirectory()) {String[] jarFileNames path.list((dir, name) - name.endsWith(.jar));for (String fileName : jarFileNames) {try {File file new File(path, fileName);Jar jar new Jar(new JarFile(file), file);jars.add(jar);LOGGER.info({} loaded., file.toString());} catch (IOException e) {LOGGER.error(e, {} jar file cant be resolved, fileName);}}}}return jars;}RequiredArgsConstructorprivate static class Jar {private final JarFile jarFile;private final File sourceFile;}
}PluginResourcesResolver 获取skywalking-plugin.def插件定义
/** Licensed to the Apache Software Foundation (ASF) under one or more* contributor license agreements. See the NOTICE file distributed with* this work for additional information regarding copyright ownership.* The ASF licenses this file to You under the Apache License, Version 2.0* (the License); you may not use this file except in compliance with* the License. You may obtain a copy of the License at** http://www.apache.org/licenses/LICENSE-2.0** Unless required by applicable law or agreed to in writing, software* distributed under the License is distributed on an AS IS BASIS,* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.* See the License for the specific language governing permissions and* limitations under the License.**/package org.apache.skywalking.apm.agent.core.plugin;import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import org.apache.skywalking.apm.agent.core.logging.api.ILog;
import org.apache.skywalking.apm.agent.core.logging.api.LogManager;
import org.apache.skywalking.apm.agent.core.plugin.loader.AgentClassLoader;/*** Use the current classloader to read all plugin define file. The file must be named skywalking-plugin.def*/
public class PluginResourcesResolver {private static final ILog LOGGER LogManager.getLogger(PluginResourcesResolver.class);public ListURL getResources() {ListURL cfgUrlPaths new ArrayListURL();EnumerationURL urls;try {urls AgentClassLoader.getDefault().getResources(skywalking-plugin.def);while (urls.hasMoreElements()) {URL pluginUrl urls.nextElement();cfgUrlPaths.add(pluginUrl);LOGGER.info(find skywalking plugin define in {}, pluginUrl);}return cfgUrlPaths;} catch (IOException e) {LOGGER.error(read resources failure., e);}return null;}
}
