增加部分代码，提供新的应用程序入口，用于增强类实现。#36

skywalking-api/src/main/java/com/ai/cloud/skywalking/conf/ConfigInitializer.java

 package com.ai.cloud.skywalking.conf;
 
+import static com.ai.cloud.skywalking.conf.Config.SkyWalking.AUTH_OVERRIDE;
+import static com.ai.cloud.skywalking.conf.Config.SkyWalking.AUTH_SYSTEM_ENV_NAME;
+
 import java.io.IOException;
 import java.io.InputStream;
 import java.lang.reflect.Field;
 import java.lang.reflect.Modifier;
 import java.util.LinkedList;
 import java.util.Properties;
-import java.util.logging.Level;
-import java.util.logging.Logger;
 
-import static com.ai.cloud.skywalking.conf.Config.SkyWalking.*;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
 
 public class ConfigInitializer {
-    private static Logger logger = Logger.getLogger(ConfigInitializer.class.getName());
+	private static Logger logger = LogManager.getLogger(ConfigInitializer.class);
 
     public static void initialize() {
         InputStream inputStream = ConfigInitializer.class.getResourceAsStream("/sky-walking.auth");
         if (inputStream == null) {
-            logger.log(Level.ALL, "No provider sky-walking certification documents, sky-walking api auto shutdown.");
+            logger.info("No provider sky-walking certification documents, sky-walking api auto shutdown.");
         } else {
             try {
                 Properties properties = new Properties();
                 properties.load(inputStream);
                 initNextLevel(properties, Config.class, new ConfigDesc());
                 AuthDesc.isAuth = Boolean.valueOf(System.getenv(AUTH_SYSTEM_ENV_NAME));
-                logger.log(Level.ALL, "sky-walking auth check : " + AuthDesc.isAuth);
+                logger.info("sky-walking auth check : " + AuthDesc.isAuth);
                 if(!AuthDesc.isAuth && AUTH_OVERRIDE){
                 	AuthDesc.isAuth = AUTH_OVERRIDE;
-                	logger.log(Level.ALL, "sky-walking auth override: " + AuthDesc.isAuth);
+                	logger.info("sky-walking auth override: " + AuthDesc.isAuth);
                 }
             } catch (IllegalAccessException e) {
-                logger.log(Level.ALL, "Parsing certification file failed, sky-walking api auto shutdown.");
+                logger.error("Parsing certification file failed, sky-walking api auto shutdown.", e);
             } catch (IOException e) {
-                logger.log(Level.ALL, "Failed to read the certification file, sky-walking api auto shutdown.");
+                logger.error("Failed to read the certification file, sky-walking api auto shutdown.", e);
             }
         }
     }

skywalking-api/src/main/java/com/ai/cloud/skywalking/plugin/PluginBootstrap.java

+package com.ai.cloud.skywalking.plugin;
+
+import java.net.URL;
+import java.util.Enumeration;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import com.ai.cloud.skywalking.conf.AuthDesc;
+import com.ai.cloud.skywalking.plugin.interceptor.EnhanceClazz4Interceptor;
+
+public class PluginBootstrap {
+	private static Logger logger = LogManager.getLogger(PluginBootstrap.class);
+
+	public void start() {
+		if (!AuthDesc.isAuth()) {
+			return;
+		}
+
+		PluginResourcesResolver resolver = new PluginResourcesResolver();
+		Enumeration<URL> resources = resolver.getResources();
+
+		if (resources == null || !resources.hasMoreElements()) {
+			logger.info("no plugin files (skywalking-plugin.properties) found, continue to start application.");
+			return;
+		}
+
+		while (resources.hasMoreElements()) {
+			URL pluginUrl = resources.nextElement();
+			try {
+				PluginCfg.CFG.load(pluginUrl.openStream());
+			} catch (Throwable t) {
+				logger.error("plugin [{}] init failure.", pluginUrl, t);
+			}
+		}
+		
+		EnhanceClazz4Interceptor enhanceClazz4Interceptor = new EnhanceClazz4Interceptor();
+		enhanceClazz4Interceptor.enhance();
+	}
+}

skywalking-api/src/main/java/com/ai/cloud/skywalking/plugin/PluginCfg.java

+package com.ai.cloud.skywalking.plugin;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.util.HashSet;
+import java.util.Set;
+
+import com.ai.cloud.skywalking.util.StringUtil;
+
+public class PluginCfg {
+	public final static PluginCfg CFG = new PluginCfg();
+	
+	private Set<String> interceptorClassList = new HashSet<String>();
+	
+	private PluginCfg(){}
+	
+	void load(InputStream input) throws IOException{
+		try{
+			BufferedReader reader = new BufferedReader(new InputStreamReader(input));
+			String nhanceOriginClassName = null;
+			while((nhanceOriginClassName = reader.readLine()) != null){
+				if(!StringUtil.isEmpty(nhanceOriginClassName)){
+					interceptorClassList.add(nhanceOriginClassName.trim());
+				}
+			}
+		}finally{
+			input.close();
+		}
+	}
+	
+	public Set<String> getInterceptorClassList(){
+		return interceptorClassList;
+	}
+}

skywalking-api/src/main/java/com/ai/cloud/skywalking/plugin/PluginResourcesResolver.java

+package com.ai.cloud.skywalking.plugin;
+
+import java.io.IOException;
+import java.net.URL;
+import java.util.Enumeration;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+public class PluginResourcesResolver {
+	private static Logger logger = LogManager.getLogger(PluginResourcesResolver.class);
+	
+	public Enumeration<URL> getResources(){
+		Enumeration<URL> urls;
+		try {
+			urls = getDefaultClassLoader().getResources("skywalking-plugin.properties");
+			
+			if(!urls.hasMoreElements()){
+				logger.info("no plugin files (skywalking-plugin.properties) found");
+			}
+			
+			while(urls.hasMoreElements()){
+				URL pluginUrl = urls.nextElement();
+				logger.info("find skywalking plugin define in {}", pluginUrl);
+			}
+			
+			return urls;
+		} catch (IOException e) {
+			logger.error("read resources failure.", e);
+		}
+		return null;
+	}
+	
+	private ClassLoader getDefaultClassLoader() {
+		ClassLoader cl = null;
+		try {
+			cl = Thread.currentThread().getContextClassLoader();
+		}
+		catch (Throwable ex) {
+			// Cannot access thread context ClassLoader - falling back to system class loader...
+		}
+		if (cl == null) {
+			// No thread context class loader -> use class loader of this class.
+			cl = PluginResourcesResolver.class.getClassLoader();
+		}
+		return cl;
+	}
+	
+}

skywalking-api/src/main/java/com/ai/cloud/skywalking/plugin/TracingBootstrap.java

+package com.ai.cloud.skywalking.plugin;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+/**
+ * 替代应用函数的main函数入口，确保在程序入口处运行 <br/>
+ * 用于替代-javaagent的另一种模式 <br/>
+ * 
+ * @author wusheng
+ *
+ */
+public class TracingBootstrap {
+	private static Logger logger = LogManager.getLogger(TracingBootstrap.class);
+
+	private TracingBootstrap() {
+	}
+
+	public static void main(String[] args) {
+		if (args.length == 0) {
+			throw new RuntimeException(
+					"bootstrap failure. need args[0] to be main class.");
+		}
+
+		try {
+			PluginBootstrap bootstrap = new PluginBootstrap();
+			bootstrap.start();
+		} catch (Throwable t) {
+			logger.error("PluginBootstrap start failure.", t);
+		}
+
+	}
+}

skywalking-api/src/main/java/com/ai/cloud/skywalking/plugin/interceptor/EnhanceClazz4Interceptor.java

+package com.ai.cloud.skywalking.plugin.interceptor;
+
+import java.util.Set;
+
+import net.bytebuddy.ByteBuddy;
+import net.bytebuddy.dynamic.ClassFileLocator;
+import net.bytebuddy.dynamic.loading.ClassLoadingStrategy;
+import net.bytebuddy.pool.TypePool;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import com.ai.cloud.skywalking.plugin.PluginCfg;
+
+public class EnhanceClazz4Interceptor {
+	private static Logger logger = LogManager
+			.getLogger(EnhanceClazz4Interceptor.class);
+
+	private TypePool typePool;
+
+	public EnhanceClazz4Interceptor() {
+		typePool = TypePool.Default.ofClassPath();
+	}
+
+	public void enhance() {
+		Set<String> interceptorClassList = PluginCfg.CFG
+				.getInterceptorClassList();
+
+		for (String interceptorClassName : interceptorClassList) {
+			try {
+				enhance0(interceptorClassName);
+			} catch (Throwable t) {
+				logger.error("enhance class [{}] for intercept failure.",
+						interceptorClassName, t);
+			}
+		}
+	}
+
+	private void enhance0(String enhanceOriginClassName) {
+		/**
+		 * add '$$Origin' at the end of be enhanced classname <br/>
+		 * such as: class com.ai.cloud.TestClass to class com.ai.cloud.TestClass$$Origin
+		 */
+		new ByteBuddy()
+				.redefine(typePool.describe(enhanceOriginClassName).resolve(),
+						ClassFileLocator.ForClassLoader.ofClassPath())
+				.name(enhanceOriginClassName + "$$Origin")
+				.make()
+				.load(ClassLoader.getSystemClassLoader(),
+						ClassLoadingStrategy.Default.INJECTION).getLoaded();
+	}
+}

skywalking-api/src/main/java/com/ai/cloud/skywalking/selfexamination/SDKHealthCollector.java

@@ -12,7 +12,7 @@ import com.ai.cloud.skywalking.conf.Config;
 import com.ai.cloud.skywalking.util.BuriedPointMachineUtil;
 
 public class SDKHealthCollector extends Thread {
-	private Logger logger = LogManager.getLogger(SDKHealthCollector.class);
+	private static Logger logger = LogManager.getLogger(SDKHealthCollector.class);
 
 	private static Map<String, HeathReading> heathReadings = new ConcurrentHashMap<String, HeathReading>();
 

skywalking-api/src/test/java/test/ai/cloud/plugin/PluginResourceResoverTest.java

+package test.ai.cloud.plugin;
+
+import java.io.IOException;
+
+import com.ai.cloud.skywalking.plugin.PluginResourcesResolver;
+
+public class PluginResourceResoverTest {
+
+	public static void main(String[] args) throws IOException {
+		PluginResourcesResolver resolver = new PluginResourcesResolver();
+		resolver.getResources();
+	}
+
+}

skywalking-api/src/test/resources/log4j2.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<Configuration status="debug">
+    <Appenders>
+        <Console name="Console" target="SYSTEM_OUT">
+            <PatternLayout pattern="%d [%t](%F:%L) %-5level %logger{36} - %msg%n"/>
+        </Console>
+    </Appenders>
+    <Loggers>
+        <Root level="debug">
+            <AppenderRef ref="Console"/>
+        </Root>
+    </Loggers>
+</Configuration>
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