BTrace二三事之二：OnMethod子类婚配BUG(怀疑)

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。）

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