检测或防止 Commons Net FTPClient 在读取时阻塞
我正在使用 Commons Net FTPClient 类定期轮询 ftp 站点并尝试下载文件。有时，当尝试从网站读取数据时，线程会无限期地阻塞，我想知道是否有其他人遇到过这个问题并可以提供任何解决方法？
我使用 FTPClient 的 retrieveFileStream(String) 方法来获取 InputStream 的句柄，然后尝试从中读取。下面是被阻止线程的部分堆栈跟踪。
"FTP File Poll Thread" prio=10 tid=0x083b0800 nid=0x6324 runnable [0x65b5b000..0x65b5beb0]
java.lang.Thread.State: RUNNABLE
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
at java.io.BufferedInputStream.read(BufferedInputStream.java:237)
- locked <0x5c851928> (a java.io.BufferedInputStream)
at java.io.FilterInputStream.read(FilterInputStream.java:66)
at java.io.PushbackInputStream.read(PushbackInputStream.java:122)
at org.apache.commons.net.io.FromNetASCIIInputStream.__read(FromNetASCIIInputStream.java:75)
at org.apache.commons.net.io.FromNetASCIIInputStream.read(FromNetASCIIInputStream.java:170)
at java.io.FilterInputStream.read(FilterInputStream.java:116)
I'm using the Commons Net FTPClient class to periodically poll an ftp site and attempt to download a file. Occasionally the thread is blocking indefinitely when trying to read from the site and I wondered if anyone else had encountered this problem and could offer any workarounds?
I'm using FTPClient's retrieveFileStream(String) method to get a handle to an InputStream, which I then attempt to read from. Below is a partial stack trace of the blocked thread.
"FTP File Poll Thread" prio=10 tid=0x083b0800 nid=0x6324 runnable [0x65b5b000..0x65b5beb0]
java.lang.Thread.State: RUNNABLE
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
at java.io.BufferedInputStream.read(BufferedInputStream.java:237)
- locked <0x5c851928> (a java.io.BufferedInputStream)
at java.io.FilterInputStream.read(FilterInputStream.java:66)
at java.io.PushbackInputStream.read(PushbackInputStream.java:122)
at org.apache.commons.net.io.FromNetASCIIInputStream.__read(FromNetASCIIInputStream.java:75)
at org.apache.commons.net.io.FromNetASCIIInputStream.read(FromNetASCIIInputStream.java:170)
at java.io.FilterInputStream.read(FilterInputStream.java:116)
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java.io是阻塞的，需要使用java.nio包。从未将 ftp 与 java.nio 一起使用，但假设它一定可以工作，因为 http 可以与 java.nio 一起工作。
问候
java.io is blocking, you need to use the java.nio package. Never used ftp with java.nio, but assume it must work because http can work with java.nio.
Regards
我最终在这里使用的拼凑是安排一个任务，以便在 FTP 操作花费的时间超过 X 秒时发出警报。我确实在 Sourceforge 上找到了 javanioftp 但在我的情况下，它不保证切换时的开发开销客户。
The kludge I ended up using here was to schedule a task to raise an alert if the FTP operation took longer than X seconds. I did actually find javanioftp on Sourceforge but in my situation it doesn't warrant the development overhead in switching clients.