Java-重置InputStream [英] Java - Resetting InputStream

问题描述

我正在处理一些Java代码，其中读取了一个InputStream，然后需要使用相同的方法再次读取它.

I'm dealing with some Java code in which there's an InputStream that I read one time and then I need to read it once again in the same method.

问题是我需要将其位置重置为开始才能读取两次.

The problem is that I need to reset it's position to the start in order to read it twice.

我找到了解决该问题的方法:

I've found a hack-ish solution to the problem:

is.mark(Integer.MAX_VALUE);

//Read the InputStream is fully
// { ... }

try
{
    is.reset();
}
catch (IOException e)
{
    e.printStackTrace();
}

此解决方案是否会导致某些无法预期的行为?还是在愚蠢的情况下会起作用?

Does this solution lead to some unespected behaviours? Or it will work in it's dumbness?

推荐答案

按照书面说明，您不能保证，因为不需要 mark()报告其是否成功.要获得保证，您必须先致电

As written, you have no guarantees, because mark() is not required to report whether it was successful. To get a guarantee, you must first call markSupported(), and it must return true.

如所写，指定的读取限制也是非常危险的.如果您碰巧使用的是在内存中缓冲的流，则它可能会分配2GB的缓冲区.另一方面，如果碰巧正在使用 FileInputStream ，就可以了.

Also as written, the specified read limit is very dangerous. If you happen to be using a stream that buffers in-memory, it will potentially allocate a 2GB buffer. On the other hand, if you happen to be using a FileInputStream, you're fine.

更好的方法是将 BufferedInputStream 与显式缓冲区一起使用.

A better approach is to use a BufferedInputStream with an explicit buffer.

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