java - 如何在 Java jdb 中跳过断点一定次数？

Question

如何在 jdb 中跳过指定次数的断点？

jdb的帮助提供了这样的提示:

!!                        -- repeat last command
<n> <command>             -- repeat command n times
# <command>               -- discard (no-op)

当我尝试跳过 n 次断点时，如下所示:

80 cont

或者像这样:

80 run

jdb barfs:

main[1] 80 cont
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.

Breakpoint hit: main[1] > Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.Exception in thread "event-handler" java.lang.NullPointerException
        at com.sun.tools.example.debug.tty.TTY.printCurrentLocation(TTY.java:212)
        at com.sun.tools.example.debug.tty.TTY.vmInterrupted(TTY.java:189)
        at com.sun.tools.example.debug.tty.EventHandler.run(EventHandler.java:86)
        at java.lang.Thread.run(Thread.java:619)

> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.
> Nothing suspended.

这里发生了什么？如何获得所需的行为？

版本:

> version
This is jdb version 1.6 (J2SE version 1.6.0_16)
Java Debug Interface (Reference Implementation) version 1.6
Java Debug Wire Protocol (Reference Implementation) version 1.6
JVM Debug Interface version 1.1
JVM version 1.6.0_17 (Java HotSpot(TM) Client VM, mixed mode, sharing)

澄清一下，我正在远程调试。例如，我的第一个窗口是这样启动的:

% java -Xdebug -Xrunjdwp:transport=dt_socket,address=8000,server=y,suspend=n LZWDecompress

我的第二个窗口是这样开始的:

% jdb -connect com.sun.jdi.SocketAttach:hostname=localhost,port=8000

Answer 1

不幸的是，jdb 中的断点不提供任何奇特的功能，例如条件断点或“每 n 次迭代停止一次”。

但是，由于无论如何您都在远程连接，您可能需要考虑在编辑器中使用调试器，因为大多数编辑器都会让您连接到远程机器。由于大部分的调试工作都是在JVM中完成的，而只有显示是由编辑器完成的，所以不会比使用jdb慢多少。