关闭 BufferedReader 而不关闭包装流 [英] Closing BufferedReader without closing wrapped stream

问题描述

我目前正在编写一个使用 TCP 套接字与服务器通信的程序.其中一部分需要通过多种方法来回发送信息.但是，我不想为每个请求打开一个新的套接字连接，但我不能保证请求的数量或顺序.为了解决这个问题，我只保留了一个可以重复使用的套接字实例.

I'm currently writing a program that communicates with a server using TCP sockets. Part of that requires sending information back and forth through several methods. However, I do not want to open up a new socket connection for each request, but I can't guarantee the number or the order of the requests. In order to handle this, I simply keep one socket instance that gets reused a lot.

然而，为了读取数据，我使用了 BufferedReader 包装类.因为我重用了同一个套接字，所以我不能在阅读器上调用 close() ，否则我也会关闭套接字流.

However, in order to read the data I use BufferedReader wrapper classes. Because I reuse the same socket, I can't call close() on the reader, or I'll close the socket stream as well.

如果我不想关闭底层流，是否需要在 BufferedReader 上调用 close()?不这样做会导致内存泄漏吗?如果我确实需要调用 close() 如何在不关闭套接字流的情况下返回内存?

Do I need to call close() on the BufferedReader if I don't want to close the underlying stream? Will I cause a memory leak by not doing this? If I do need to call close() how can I return the memory without closing the socket's stream?

注意:我将在程序终止时关闭底层流，这个问题与此无关.

Note: I will close the underlying stream at program termination, this question isn't about that.

推荐答案

不要关闭 BufferedReade.更重要的，不要丢弃BufferedReader；相反，传递它而不是 SocketInputStream.

Don't close the BufferedReade. More important, don't discard the BufferedReader; instead, pass it around rather than the SocketInputStream.

BufferedReader，顾名思义，有一个内部缓冲区.当您读取它时，它会尝试从底层 Reader 填充该缓冲区.这意味着，如果你丢弃它，那些字节就会消失.

A BufferedReader, as its name implies, has an internal buffer. When you read from it, it tries to fill that buffer from the underlying Reader. Which means that, if you discard it, those bytes are gone.

现在是一些未经询问的建议:

And now some unasked advice:

• 您真的要使用 Reader 吗?大多数通信协议使用 DataInputStream/DataOutputStream 可以更好地实现.使用 Reader，您只能读取字符数据(对于 BR，则是字符数据行).
• 您是否关注编码?在 InputStream 之上构造 Reader 的正确方法是使用 InputStreamReader 的两个参数变体: new InputStreamReader(in, "UTF-8")(您可以使用 UTF-8 以外的编码，但有充分的理由).
• 通常最好使用 BufferedInputStream 而不是 BufferedReader，因为从流到读取器的转换可能涉及多次读取.如果你想要 readLine()，你可以同时使用两者.
• 确保在 finally 或 try-with-resources 中关闭 socket.请参阅此了解更多信息.

• Do you really want to use a Reader? Most communication protocols are better implemented using a DataInputStream/DataOutputStream. With a Reader you're limited to character data (and in the case of BR, lines of character data).
• Are you paying attention to encoding? The correct way to construct a Reader on top of an InputStream is to use the two-argument variant of InputStreamReader: new InputStreamReader(in, "UTF-8") (you can use an encoding other than UTF-8, but have a good reason).
• It's generally better to use a BufferedInputStream rather than a BufferedReader, because the translation from stream to reader may involve multiple reads. If you want readLine(), you can always use both.
• Be sure to close the socket in either a finally or try-with-resources. See this for more info.

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