为什么chdir在Java中不支持？

Question

我想知道Java为什么不提供chdir调用实现，却提供相同的本机接口的真正原因。

Answer 1

The full evaluation can be found in Sun/Oracle's bug database with issue number JDK-4045688 : Add chdir or equivalent notion of changing working directory

It was decided to close the ticket because there are major issues with any solution, and none of the customers that reported the bug really needed it - all of them were able to use a workaround.

One excerpt from the bug database that highlights the issues with adding such a call:

EVALUATION

This feature can be interpreted in two ways: chdir could change the current working directory of the process containing the JVM, causing all threads to change simultaneously, or to provide a more "virtual" per-thread concept of current directory, which could conceptually be a ThreadLocal. This would be merely a convenience for building up complete path names to pass to the underlying operating system API.

This is how the current directory works in Emacs - it's just a variable, but a magic one that can have buffer-local values. Emacs buffers are kinda sorta like Java threads in this sense. Such an implementation would offer convenience and safety. Having each thread with a ThreadLocal current directory gives a programmer experience familiar to old Unix greybeards, except that Threads replace Processes.

Many workarounds are also described there, such as executing a subprocess with a new current directory, or always qualifying your file accesses with the parent directory from where you want your relative part to start.