Add sniffer core classes’s comments. #78

skywalking-sniffer/skywalking-agent/src/main/java/com/a/eye/skywalking/agent/SkyWalkingAgent.java

@@ -24,6 +24,12 @@ import java.net.URL;
 import static net.bytebuddy.matcher.ElementMatchers.isInterface;
 import static net.bytebuddy.matcher.ElementMatchers.not;
 
+/**
+ * The main entrance of sky-waking agent.
+ * It bases on javaagent mechanism.
+ *
+ * @author wusheng
+ */
 public class SkyWalkingAgent {
     static {
         LogManager.setLogResolver(new EasyLogResolver());
@@ -31,6 +37,14 @@ public class SkyWalkingAgent {
 
     private static ILog logger;
 
+    /**
+     * Main entrance.
+     * Use byte-buddy transform to enhance all classes, which define in plugins.
+     *
+     * @param agentArgs
+     * @param instrumentation
+     * @throws PluginException
+     */
     public static void premain(String agentArgs, Instrumentation instrumentation) throws PluginException {
         logger = LogManager.getLogger(SkyWalkingAgent.class);
 
@@ -64,7 +78,13 @@ public class SkyWalkingAgent {
         }).installOn(instrumentation);
     }
 
-
+    /**
+     * Get the enhance target classes matcher.
+     *
+     * @param pluginDefineCategory
+     * @param <T>
+     * @return class matcher.
+     */
     private static <T extends NamedElement> ElementMatcher.Junction<T> enhanceClassMatcher(PluginDefineCategory pluginDefineCategory) {
         return new SkyWalkingEnhanceMatcher<T>(pluginDefineCategory);
     }
@@ -81,6 +101,12 @@ public class SkyWalkingAgent {
         ConfigInitializer.initialize();
     }
 
+    /**
+     * Try to allocate the skywalking-agent.jar
+     * Some config files or output resources are from this path.
+     *
+     * @return the path, where the skywalking-agent.jar is.
+     */
     private static String initAgentBasePath() {
         try {
             String urlString = SkyWalkingAgent.class.getClassLoader().getSystemClassLoader().getResource(generateLocationPath()).toString();

skywalking-sniffer/skywalking-agent/src/main/java/com/a/eye/skywalking/agent/junction/SkyWalkingEnhanceMatcher.java

@@ -4,6 +4,9 @@ import com.a.eye.skywalking.plugin.PluginDefineCategory;
 import net.bytebuddy.description.NamedElement;
 
 /**
+ * The matcher bases on byte-buddy {@link AbstractJunction} class.
+ * Judge the target class in transforming, should be enhanced or not.
+ * <p>
  * Created by wusheng on 16/7/31.
  */
 public class SkyWalkingEnhanceMatcher<T extends NamedElement> extends AbstractJunction<T> {

skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/context/CurrentThreadSpanStack.java

@@ -6,6 +6,14 @@ import com.a.eye.skywalking.model.Span;
 import java.util.ArrayList;
 import java.util.List;
 
+/**
+ * Core in-process propagation context accessor.
+ * You can push, peek, pop {@link Span}s.
+ * In processing, every span be created and pushed into the context when begin
+ * This context based on stack structure. see the stack on {@link SpanNodeStack}
+ *
+ * @author wusheng
+ */
 public class CurrentThreadSpanStack {
     private static ThreadLocal<SpanNodeStack> nodes = new ThreadLocal<SpanNodeStack>();
 
@@ -36,8 +44,8 @@ public class CurrentThreadSpanStack {
 
     static class SpanNodeStack {
         /**
-         * 单JVM的单线程,埋点数量一般不会超过20.
-         * 超过20会影响性能,不推荐使用
+         * The depth of call stack should less than 20, in most cases.
+         * The depth is calculated by span, not class or the depth of java stack.
          */
         private List<SpanNode> spans = new ArrayList<SpanNode>(20);
 

skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/invoke/monitor/BaseInvokeMonitor.java

@@ -10,15 +10,18 @@ import com.a.eye.skywalking.model.ContextData;
 import com.a.eye.skywalking.model.Identification;
 import com.a.eye.skywalking.model.Span;
 import com.a.eye.skywalking.model.SpanTagBuilder;
-import com.a.eye.skywalking.network.dependencies.com.google.protobuf.ByteString;
 import com.a.eye.skywalking.network.grpc.AckSpan;
 import com.a.eye.skywalking.network.grpc.RequestSpan;
-import com.a.eye.skywalking.network.model.Tag;
 import com.a.eye.skywalking.util.BuriedPointMachineUtil;
 
 import java.util.HashSet;
 import java.util.Set;
 
+/**
+ * Basic invoke monitor.
+ *
+ * @author wusheng
+ */
 public abstract class BaseInvokeMonitor {
 
     private static ILog easyLogger = LogManager.getLogger(BaseInvokeMonitor.class);
@@ -27,10 +30,18 @@ public abstract class BaseInvokeMonitor {
 
     private static Set<String> exclusiveExceptionSet = null;
 
+    /**
+     * Create the request span before invoke method.
+     *
+     * @param spanData {@link Span} represents the before invoke.
+     * @param id
+     * @return
+     */
     protected ContextData beforeInvoke(Span spanData, Identification id) {
         if (Config.BuriedPoint.PRINTF) {
-            easyLogger.debug("TraceId:" + spanData.getTraceId() + "\tParentLevelId:" + spanData.getParentLevel()
-                    + "\tLevelId:" + spanData.getLevelId() + "\tbusinessKey:" + spanData.getBusinessKey());
+            easyLogger
+                    .debug("TraceId:" + spanData.getTraceId() + "\tParentLevelId:" + spanData.getParentLevel() + "\tLevelId:" + spanData.getLevelId() + "\tbusinessKey:" + spanData
+                            .getBusinessKey());
         }
 
         // 将新创建的Context存放到ThreadLocal栈中。
@@ -42,24 +53,33 @@ public abstract class BaseInvokeMonitor {
         return new ContextData(spanData);
     }
 
+    /**
+     * Change the {@link Span} to {@link RequestSpan}, and prepare to send to routing server.
+     *
+     * @param span
+     * @param id
+     */
     protected void sendRequestSpan(Span span, Identification id) {
-        RequestSpan requestSpan= SpanTagBuilder.newBuilder(span)
-                .setBusinessKey(id.getBusinessKey())
-                .setSpanTypeDesc(id.getSpanTypeDesc()).setCallType(id.getCallType())
-                .setProcessNo(BuriedPointMachineUtil.getProcessNo())
-                .setAddress(BuriedPointMachineUtil.getHostDesc()).buildRequestSpan(RequestSpan.newBuilder());
+        RequestSpan requestSpan = SpanTagBuilder.newBuilder(span).setBusinessKey(id.getBusinessKey()).setSpanTypeDesc(id.getSpanTypeDesc()).setCallType(id.getCallType())
+                .setProcessNo(BuriedPointMachineUtil.getProcessNo()).setAddress(BuriedPointMachineUtil.getHostDesc()).buildRequestSpan(RequestSpan.newBuilder());
 
         RequestSpanDisruptor.INSTANCE.ready2Send(requestSpan);
     }
 
+    /**
+     * Change the {@link Span} to {@link AckSpan}, and prepare to send to routing server.
+     *
+     * @param span
+     */
     protected void sendAckSpan(Span span) {
-        AckSpan ackSpan = SpanTagBuilder.newBuilder(span)
-                .setStatusCode(span.getStatusCode())
-                .setExceptionStack(span.getExceptionStack()).buildAckSpan(AckSpan.newBuilder());
+        AckSpan ackSpan = SpanTagBuilder.newBuilder(span).setStatusCode(span.getStatusCode()).setExceptionStack(span.getExceptionStack()).buildAckSpan(AckSpan.newBuilder());
 
         AckSpanDisruptor.INSTANCE.ready2Send(ackSpan);
     }
 
+    /**
+     * Create the ack span before invoke method.
+     */
     protected void afterInvoke() {
         try {
 
@@ -67,8 +87,8 @@ public abstract class BaseInvokeMonitor {
             Span spanData = CurrentThreadSpanStack.pop();
 
             if (Config.BuriedPoint.PRINTF) {
-                easyLogger.debug("TraceId-ACK:" + spanData.getTraceId() + "\tParentLevelId:" + spanData.getParentLevel()
-                        + "\tLevelId:" + spanData.getLevelId() + "\tbusinessKey:" + spanData.getBusinessKey());
+                easyLogger.debug("TraceId-ACK:" + spanData.getTraceId() + "\tParentLevelId:" + spanData.getParentLevel() + "\tLevelId:" + spanData.getLevelId() + "\tbusinessKey:"
+                        + spanData.getBusinessKey());
             }
 
             sendAckSpan(spanData);
@@ -77,6 +97,11 @@ public abstract class BaseInvokeMonitor {
         }
     }
 
+    /**
+     * Process when method invocation occurs exception.
+     *
+     * @param th
+     */
     protected void occurException(Throwable th) {
         try {
             if (exclusiveExceptionSet == null) {

skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/plugin/PluginBootstrap.java

@@ -8,11 +8,22 @@ import java.net.URL;
 import java.util.ArrayList;
 import java.util.List;
 
+/**
+ * Plugins finder.
+ * Use {@link PluginResourcesResolver} to find all plugins,
+ * and ask {@link PluginCfg} to load all plugin definitions.
+ *
+ * @author wusheng
+ */
 public class PluginBootstrap {
     private static ILog logger = LogManager.getLogger(PluginBootstrap.class);
 
     public static TypePool CLASS_TYPE_POOL = null;
 
+    /**
+     * load all plugins.
+     * @return plugin definition list.
+     */
     public List<AbstractClassEnhancePluginDefine> loadPlugins() {
         CLASS_TYPE_POOL = TypePool.Default.ofClassPath();
 

skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/plugin/PluginDefineCategory.java

@@ -4,22 +4,25 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
+/**
+ * Just category the plugins.
+ * Change the store structure from {@link List} to {@link Map}
+ */
 public class PluginDefineCategory {
 
     private static PluginDefineCategory pluginDefineCategory;
 
-    private final Map<String, AbstractClassEnhancePluginDefine> exactClassEnhancePluginDefineMapping  =
-            new HashMap<String, AbstractClassEnhancePluginDefine>();
+    private final Map<String, AbstractClassEnhancePluginDefine> exactClassEnhancePluginDefineMapping = new HashMap<String, AbstractClassEnhancePluginDefine>();
 
     private PluginDefineCategory(List<AbstractClassEnhancePluginDefine> plugins) {
         for (AbstractClassEnhancePluginDefine plugin : plugins) {
             String enhanceClassName = plugin.enhanceClassName();
 
-            if (enhanceClassName == null){
+            if (enhanceClassName == null) {
                 continue;
             }
 
-                exactClassEnhancePluginDefineMapping.put(enhanceClassName, plugin);
+            exactClassEnhancePluginDefineMapping.put(enhanceClassName, plugin);
         }
     }
 

skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/plugin/PluginResourcesResolver.java

@@ -9,45 +9,57 @@ import java.util.ArrayList;
 import java.util.Enumeration;
 import java.util.List;
 
+/**
+ * Use the current classloader to read all plugin define file.
+ * The file must be named 'skywalking-plugin.def'
+ *
+ * @author wusheng
+ */
 public class PluginResourcesResolver {
-	private static ILog logger = LogManager.getLogger(PluginResourcesResolver.class);
-	
-	public List<URL> getResources(){
-		List<URL> cfgUrlPaths = new ArrayList<URL>();
-		Enumeration<URL> urls;
-		try {
-			urls = getDefaultClassLoader().getResources("skywalking-plugin.def");
-			
-			if(!urls.hasMoreElements()){
-				logger.info("no plugin files (skywalking-plugin.properties) found");
-			}
-			
-			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;
-	}
-	
-	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;
-	}
-	
+    private static ILog logger = LogManager.getLogger(PluginResourcesResolver.class);
+
+    public List<URL> getResources() {
+        List<URL> cfgUrlPaths = new ArrayList<URL>();
+        Enumeration<URL> urls;
+        try {
+            urls = getDefaultClassLoader().getResources("skywalking-plugin.def");
+
+            if (!urls.hasMoreElements()) {
+                logger.info("no plugin files (skywalking-plugin.def) found");
+            }
+
+            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;
+    }
+
+    /**
+     * Get the classloader.
+     * First get current thread's classloader,
+     * if fail, get {@link PluginResourcesResolver}'s classloader.
+     *
+     * @return the classloader to find plugin definitions.
+     */
+    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-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/plugin/bytebuddy/AllObjectDefaultMethodsMatch.java

@@ -23,6 +23,9 @@ public enum AllObjectDefaultMethodsMatch implements ElementMatcher<MethodDescrip
      */
     private final ElementMatcher.Junction<MethodDescription> matcher;
 
+    /**
+     * Init the match, include {@link Object}'s methods.
+     */
     AllObjectDefaultMethodsMatch() {
         ElementMatcher.Junction<MethodDescription>[] allDefaultMethods = new ElementMatcher.Junction[] {named("finalize").and(takesArguments(0)).and(ElementMatchers.<MethodDescription>isPublic()),
                 named("wait").and(takesArguments(0)).and(ElementMatchers.<MethodDescription>isPublic()),
@@ -48,6 +51,10 @@ public enum AllObjectDefaultMethodsMatch implements ElementMatcher<MethodDescrip
         matcher = newMatcher;
     }
 
+    /**
+     * @param target method description.
+     * @return true, if the method inherit from {@link Object}'s methods.
+     */
     @Override
     public boolean matches(MethodDescription target) {
         return matcher.matches(target);

skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/plugin/interceptor/ConstructorInterceptPoint.java

@@ -4,14 +4,24 @@ import net.bytebuddy.description.method.MethodDescription;
 import net.bytebuddy.matcher.ElementMatcher;
 
 /**
+ * One of the three "Intercept Point".
+ * "Intercept Point" is a definition about where and how intercept happens.
+ * In this "Intercept Point", the definition targets class's constructors, and the interceptor.
+ * <p>
+ * ref to two others: {@link StaticMethodsInterceptPoint} and {@link InstanceMethodsInterceptPoint}
+ * <p>
  * Created by wusheng on 2016/11/29.
  */
-public interface ConstructorInterceptPoint{
+public interface ConstructorInterceptPoint {
+    /**
+     * Constructor matcher
+     *
+     * @return matcher instance.
+     */
     ElementMatcher<MethodDescription> getConstructorMatcher();
 
     /**
-     *
-     * @return represents a class name, the class instance must instanceof InstanceConstructorInterceptor.
+     * @return represents a class name, the class instance must be a instance of {@link com.a.eye.skywalking.plugin.interceptor.enhance.InstanceConstructorInterceptor}.
      */
     String getConstructorInterceptor();
 }

skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/plugin/interceptor/InstanceMethodsInterceptPoint.java

@@ -4,13 +4,19 @@ import net.bytebuddy.description.method.MethodDescription;
 import net.bytebuddy.matcher.ElementMatcher;
 
 /**
+ * One of the three "Intercept Point".
+ * "Intercept Point" is a definition about where and how intercept happens.
+ * In this "Intercept Point", the definition targets class's instance methods, and the interceptor.
+ *
+ * ref to two others: {@link ConstructorInterceptPoint} and {@link StaticMethodsInterceptPoint}
+ *
  * Created by wusheng on 2016/11/29.
  */
 public interface InstanceMethodsInterceptPoint {
     /**
-     * 返回需要被增强的方法列表
+     * class instance methods matcher.
      *
-     * @return
+     * @return methods matcher
      */
     ElementMatcher<MethodDescription> getMethodsMatcher();
 

skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/plugin/interceptor/StaticMethodsInterceptPoint.java

@@ -4,19 +4,24 @@ import net.bytebuddy.description.method.MethodDescription;
 import net.bytebuddy.matcher.ElementMatcher;
 
 /**
+ * One of the three "Intercept Point".
+ * "Intercept Point" is a definition about where and how intercept happens.
+ * In this "Intercept Point", the definition targets class's static methods, and the interceptor.
+ *
+ * ref to two others: {@link ConstructorInterceptPoint} and {@link InstanceMethodsInterceptPoint}
+ *
  * Created by wusheng on 2016/11/29.
  */
 public interface StaticMethodsInterceptPoint {
     /**
-     * 返回需要被增强的方法列表
+     * static methods matcher.
      *
-     * @return
+     * @return matcher instance.
      */
     ElementMatcher<MethodDescription> getMethodsMatcher();
 
     /**
-     *
-     * @return represents a class name, the class instance must instanceof StaticMethodsAroundInterceptor.
+     * @return represents a class name, the class instance must instanceof {@link com.a.eye.skywalking.plugin.interceptor.enhance.StaticMethodsAroundInterceptor}.
      */
     String getMethodsInterceptor();
 }

skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/plugin/interceptor/enhance/ConstructorInvokeContext.java

 package com.a.eye.skywalking.plugin.interceptor.enhance;
 
+/**
+ * Constructor context.
+ *
+ * @author wusheng
+ */
 public class ConstructorInvokeContext {
 	/**
-	 * 代理对象实例
+	 * object instance
 	 */
 	private Object objInst;
 	/**
-	 * 构造函数参数
+	 * constructor's arguments list.
 	 */
 	private Object[] allArguments;
 	
@@ -14,11 +19,17 @@ public class ConstructorInvokeContext {
 		this.objInst = objInst;
 		this.allArguments = allArguments;
 	}
-	
+
+	/**
+	 * @return object instance
+	 */
 	public Object inst(){
 		return objInst;
 	}
 
+	/**
+	 * @return arguments list.
+	 */
 	public Object[] allArguments(){
 		return this.allArguments;
 	}

skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/plugin/interceptor/enhance/InstanceConstructorInterceptor.java

@@ -3,8 +3,17 @@ package com.a.eye.skywalking.plugin.interceptor.enhance;
 import com.a.eye.skywalking.plugin.interceptor.EnhancedClassInstanceContext;
 
 /**
+ * The instance constructor's interceptor interface.
+ * Any plugin, which wants to intercept constructor, must implement this interface.
+ * <p>
  * Created by wusheng on 2016/11/29.
  */
 public interface InstanceConstructorInterceptor {
+    /**
+     * Called before the origin constructor invocation.
+     *
+     * @param context            a new added instance field
+     * @param interceptorContext constructor invocation context.
+     */
     void onConstruct(EnhancedClassInstanceContext context, ConstructorInvokeContext interceptorContext);
 }

skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/plugin/interceptor/enhance/InstanceMethodsAroundInterceptor.java

@@ -3,10 +3,10 @@ package com.a.eye.skywalking.plugin.interceptor.enhance;
 import com.a.eye.skywalking.plugin.interceptor.EnhancedClassInstanceContext;
 
 /**
- *
  * A interceptor, which intercept method's invocation.
  * The target methods will be defined in {@link ClassEnhancePluginDefine}'s subclass, most likely in {@link ClassInstanceMethodsEnhancePluginDefine}
  *
+ * @author wusheng
  */
 public interface InstanceMethodsAroundInterceptor {
 	/**
@@ -21,7 +21,7 @@ public interface InstanceMethodsAroundInterceptor {
 	 * called after target method invocation. Even method's invocation triggers an exception.
 	 * @param context instance context, a class instance only has one {@link EnhancedClassInstanceContext} instance.
 	 * @param interceptorContext method context, includes class name, method name, etc.
-	 * @param ret the method's return original value.
+	 * @param ret the method's original return value.
 	 * @return the method's actual return value.
 	 */
 	Object afterMethod(EnhancedClassInstanceContext context, InstanceMethodInvokeContext interceptorContext, Object ret);

skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/plugin/interceptor/enhance/MethodInterceptResult.java

 package com.a.eye.skywalking.plugin.interceptor.enhance;
 
+import com.a.eye.skywalking.plugin.interceptor.EnhancedClassInstanceContext;
+
 /**
- * 通过拦截器的before方法,指定被拦截方法的返回值,不再调用原始方法取得返回值
+ * This is a method return value manipulator.
+ * When a interceptor's method, such as {@link InstanceMethodsAroundInterceptor#beforeMethod(EnhancedClassInstanceContext, InstanceMethodInvokeContext, MethodInterceptResult)}, has this as a method argument,
+ * the interceptor can manipulate the method's return value.
+ * <p>
+ * The new value set to this object, by {@link MethodInterceptResult#defineReturnValue(Object)}, will override the origin return value.
+ *
+ * @author wusheng
  */
 public class MethodInterceptResult {
-	private boolean isContinue = true;
-	
-	private Object _ret = null;
-	
-	public void defineReturnValue(Object ret){
-		this.isContinue = false;
-		this._ret = ret;
-	}
+    private boolean isContinue = true;
+
+    private Object _ret = null;
+
+    /**
+     * define the new return value.
+     *
+     * @param ret new return value.
+     */
+    public void defineReturnValue(Object ret) {
+        this.isContinue = false;
+        this._ret = ret;
+    }
+
+    /**
+     * @return true, will trigger method interceptor({@link ClassInstanceMethodsInterceptor} and {@link ClassStaticMethodsInterceptor}) to invoke the origin method. Otherwise, not.
+     */
+    public boolean isContinue() {
+        return isContinue;
+    }
 
-	public boolean isContinue() {
-		return isContinue;
-	}
-	
-	Object _ret(){
-		return _ret;
-	}
+    /**
+     * @return the new return value.
+     */
+    Object _ret() {
+        return _ret;
+    }
 }

skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/plugin/interceptor/enhance/StaticMethodsAroundInterceptor.java

 package com.a.eye.skywalking.plugin.interceptor.enhance;
 
 
+/**
+ * The static method's interceptor interface.
+ * Any plugin, which wants to intercept static methods, must implement this interface.
+ *
+ * @author wusheng
+ */
 public interface StaticMethodsAroundInterceptor {
-	void beforeMethod(StaticMethodInvokeContext interceptorContext, MethodInterceptResult result);
-	
-	Object afterMethod(StaticMethodInvokeContext interceptorContext, Object ret);
-	
-	void handleMethodException(Throwable t, MethodInvokeContext interceptorContext);
+    /**
+     * called before target method invocation.
+     *
+     * @param interceptorContext method context, includes class name, method name, etc.
+     * @param result             change this result, if you want to truncate the method.
+     */
+    void beforeMethod(StaticMethodInvokeContext interceptorContext, MethodInterceptResult result);
+
+    /**
+     * called after target method invocation. Even method's invocation triggers an exception.
+     *
+     * @param interceptorContext method context, includes class name, method name, etc.
+     * @param ret                the method's original return value.
+     * @return the method's actual return value.
+     */
+    Object afterMethod(StaticMethodInvokeContext interceptorContext, Object ret);
+
+    /**
+     * called when occur exception.
+     *
+     * @param t                  the exception occur.
+     * @param interceptorContext method context, includes class name, method name, etc.
+     */
+    void handleMethodException(Throwable t, MethodInvokeContext interceptorContext);
 }

skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/plugin/interceptor/loader/InterceptorInstanceLoader.java

@@ -13,6 +13,12 @@ import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.locks.ReentrantLock;
 
 /**
+ * The Classloader controller.
+ * This is a very important class in sky-walking's auto-instrumentation mechanism.
+ * If you want to fully understand why need this, and how it works, you need have knowledge about Classloader appointment mechanism.
+ * <p>
+ * The loader will load a class, and focus the target class loader (be intercepted class's classloader) loads it.
+ * <p>
  * Created by wusheng on 16/8/2.
  */
 public class InterceptorInstanceLoader {
@@ -56,12 +62,13 @@ public class InterceptorInstanceLoader {
     }
 
     /**
-     * 通过二进制读取,直接加载类文件,然后通过上下文所需的classLoader强制加载
+     * load class from class binary files.
+     * Most likely all the interceptor implementations should be loaded by this.
      *
-     * @param className
-     * @param targetClassLoader
+     * @param className         interceptor class name.
+     * @param targetClassLoader the classloader, which should load the interceptor.
      * @param <T>
-     * @return
+     * @return interceptor instance.
      * @throws InvocationTargetException
      * @throws IllegalAccessException
      * @throws InstantiationException
@@ -111,12 +118,13 @@ public class InterceptorInstanceLoader {
     }
 
     /**
-     * 在当前classloader中查找是否已经加载此类。
+     * Find loaded class in the current classloader.
+     * Just in case some classes have already been loaded for some reasons.s
      *
-     * @param className
-     * @param targetClassLoader
+     * @param className         interceptor class name.
+     * @param targetClassLoader the classloader, which should load the interceptor.
      * @param <T>
-     * @return
+     * @return interceptor instance.
      */
     private static <T> T findLoadedClass(String className, ClassLoader targetClassLoader) throws InvocationTargetException, IllegalAccessException, InstantiationException {
         Method defineClassMethod = null;

skywalking-sniffer/skywalking-toolkit-activation/skywalking-toolkit-opentracing-activation/src/main/java/com/a/eye/skywalking/toolkit/activation/opentracing/SkyWalkingTracerActivation.java

 package com.a.eye.skywalking.toolkit.activation.opentracing;
 
-import com.a.eye.skywalking.plugin.bytebuddy.ArgumentTypeNameMatch;
 import com.a.eye.skywalking.plugin.interceptor.ConstructorInterceptPoint;
 import com.a.eye.skywalking.plugin.interceptor.InstanceMethodsInterceptPoint;
 import com.a.eye.skywalking.plugin.interceptor.enhance.ClassInstanceMethodsEnhancePluginDefine;