btrace功能列表

Btrace是一个jvm probe工具，可以灵活地声明刺探点并注入刺探逻辑。它自带的samples中有非常多的例子，本文列举了从这些例子中总结出来的刺探点声明。

构造函数刺探，重载的构造函数也可以

@BTrace public class OnThrow {    
    // store current exception in a thread local
    // variable (@TLS annotation). Note that we can't
    // store it in a global variable!
    @TLS static Throwable currentException;

    // introduce probe into every constructor of java.lang.Throwable
    // class and store "this" in the thread local variable.
    @OnMethod(
        clazz="java.lang.Throwable",
        method="<init>"
    )
    public static void onthrow(@Self Throwable self) {
        currentException = self;
    }

    @OnMethod(
        clazz="java.lang.Throwable",
        method="<init>"
    )
    public static void onthrow(@Self Throwable self, String s) {
        currentException = self;
    }

    @OnMethod(
        clazz="java.lang.Throwable",
        method="<init>"
    )
    public static void onthrow(@Self Throwable self, String s, Throwable cause) {
        currentException = self;
    }

    @OnMethod(
        clazz="java.lang.Throwable",
        method="<init>"
    )
    public static void onthrow(@Self Throwable self, Throwable cause) {
        currentException = self;
    }

    // when any constructor of java.lang.Throwable returns
    // print the currentException's stack trace.
    @OnMethod(
        clazz="java.lang.Throwable",
        method="<init>",
        location=@Location(Kind.RETURN)
    )
    public static void onthrowreturn() {
        if (currentException != null) {
            Threads.jstack(currentException);
            println("=====================");
            currentException = null;
        }
    }
}

 

刺探一个类的所有子类

@BTrace public class Classload {
   @OnMethod(
     clazz="+java.lang.ClassLoader", 
     method="defineClass",
     location=@Location(Kind.RETURN)
   )   
   public static void defineclass(@Return Class cl) {
       println(Strings.strcat("loaded ", Reflective.name(cl)));
       Threads.jstack();
       println("==========================");
   }
}

另一个例子，

@BTrace
public class SubtypeTracer {
    @OnMethod(
        clazz="+java.lang.Runnable",
        method="run"
    )
    public static void onRun(@ProbeClassName String pcn, @ProbeMethodName String pmn) {
        // on every Runnable.run() method entry print class.method
        print(pcn);
        print('.');
        println(pmn);
    }
}

使用正则表达式刺探多个方法

@BTrace public class AllMethods {
    @OnMethod(
        clazz="/javax\\.swing\\..*/",
        method="/.*/"
    )
    public static void m(@ProbeClassName String probeClass, @ProbeMethodName String probeMethod) {
        print(Strings.strcat("entered ", probeClass));
        println(Strings.strcat(".", probeMethod));
    }
} 

 

刺探获得锁之后以及释放锁之前

@BTrace public class AllSync {
    @OnMethod(
        clazz="/javax\\.swing\\..*/",
        method="/.*/",
        location=@Location(value=Kind.SYNC_ENTRY, where=Where.AFTER) 
    )
    public static void onSyncEntry(Object obj) {
        println(Strings.strcat("after synchronized entry: ", identityStr(obj)));
    }

    @OnMethod(
        clazz="/javax\\.swing\\..*/",
        method="/.*/",
        location=@Location(Kind.SYNC_EXIT) 
    )
    public static void onSyncExit(Object obj) {
        println(Strings.strcat("before synchronized exit: ", identityStr(obj)));
    }
}