BTrace二三事之二：OnMethod子类匹配BUG(怀疑)

BTRace1.2.2版本
@OnMethod(clazz = "+my.Command", method="execute")
对子类的匹配（怀疑）存在BUG。

即：加载Agent之前的已载入的Class被拦截了，但Agent加载之后的Class没有拦截。

从源代码看应该是这样，涉及到子类匹配检查的主要两个变量：

hasSubclassChecks ：是否需要检查子类匹配，如果需要的话，
所有通过ClassLoader.defineClass()加载的类，会被注入一段静态初始化代码：

{
  BTraceRuntime.retransform(Ljava/lang/String;Ljava/lang/Class;)
}

作用是，在类被初始化后，立即触发类的重转换。

第二个变量是：skipRetransforms：是否跳过类的重转换，
当Agent加载后，如果已经存在部分类发生了转换，那么这个变量会被设置为true，
从而导致后续类没有被拦截。

BTraceHost：

public interface Command {
	void execute();
}

public class Foo1Command implements Command {
public void execute() {
	System.out.println("foo1 command execute...");
}
}

public class Foo2Command implements Command {
public void execute() {
	System.out.println("foo2 command execute...");
}
}

public class HostMain {
public static void main(String[] args) {
	System.out.println("pid = " + getSelfPID());
	new Thread(new Spy()).start();
}
static String getSelfPID() {
	String pname = ManagementFactory.getRuntimeMXBean().getName();
	int index = pname.indexOf('@');
	if (index == -1) {
		throw new RuntimeException("获取自身进程PID失败！进程名称为：" + pname);
	}
	String pid = pname.substring(0, index);
	return pid;
}
}

public class Spy implements Runnable {
static Map<String, String> commands = new HashMap<String, String>();
static {
	commands.put("1", "my.Foo1Command");
	commands.put("2", "my.Foo2Command");
}

public void run() {
	try {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		System.out.println("enter Command: ");
		System.out.println("commands : " + commands);
		System.out.println("请验证下面两个场景：");
		System.out.println("场景一：加载Foo1；加载Agent；加载Foo2---结果：Foo1被拦截；Foo2未拦截");
		System.out.println("场景二：加载Agent；          加载Foo2---结果：Foo1被拦截；Foo2被拦截");
		for (String line; (line = in.readLine()) != null;) {
			doAction(line);
		}
	}
	catch (Exception e) {
		e.printStackTrace();
	}
}

void doAction(String action) throws Exception {
	String commandName = commands.get(action);
	if (commandName != null) {
		Command command = (Command) Class.forName(commandName).newInstance();
		command.execute();
	}
	else {
		System.out.println("invalid command..");
		System.out.println("commands : " + commands);
	}
}
}

BTraceClient：

public class BTraceStarter {
public static void main(String[] args) throws Exception {
	String classpath = System.getProperty("java.class.path");
	if (!classpath.contains("tools.jar")) {
		throw new RuntimeException("请在类路径中设置tools.jar!");
	}
	System.setProperty("com.sun.btrace.probeDescPath", ".");
	System.setProperty("com.sun.btrace.dumpClasses", "true");
	System.setProperty("com.sun.btrace.dumpDir", "./dump");
	System.setProperty("com.sun.btrace.debug", "false");
	System.setProperty("com.sun.btrace.unsafe", "true");

	BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
	System.out.println("请输入目标进程PID： ");
	String pid = in.readLine();
	String script = new File(BTraceStarter.class.getResource("SampleScript.class").getFile()).getCanonicalPath();
	com.sun.btrace.client.Main.main(new String[] { pid, script });
}
}

@BTrace(unsafe = true)
public class SampleScript {
@OnMethod(clazz = "+my.Command", method = "execute", location = @Location(Kind.RETURN))
public static void onExecuteReturn(@ProbeClassName String className, @Duration long duration) {
	BTraceUtils.println(Strings.concat("execute return : className = ", className));
}
}

附件一：BTrace1.2.2 执行库下载；
附件二：BTrace1.2.2 源代码下载；
附件三：验证的例子；（直接运行例子中的BTraceHost和BTraceClient即可。）