是否有任何util类/方法采用大String并返回InputStream? [英] Any util class/method to take a large String and return an InputStream?

问题描述

我正在寻找一些使用util类/方法来占用较大的String并返回InputStream.

I am looking for some util class/method to take a large String and return an InputStream.

如果String很小，我可以这样做:

If the String is small, I can just do:

InputStream is = new ByteArrayInputStream(str.getBytes(<charset>));

但是，当String很大(1MB，10MB或更大)时，当场分配一个比我的String大1到2倍(或更多?)的字节数组. (而且由于在完成所有编码之前您将不知道确切分配多少字节，所以我认为在分配最终字节数组之前必须分配其他数组/缓冲区.)

But when the String is large(1MB, 10MB or more), a byte array 1 to 2 times(or more?) as large as my String is allocated on the spot. (And since you won't know how many bytes to allocate exactly before all the encoding is done, I think there must be other arrays/buffers allocated before the final byte array is allocated).

我对性能有要求，并且想优化此操作.

I have performance requirements, and want to optimize this operation.

理想情况下，我认为，正在寻找的类/方法会在消耗InputStream的同时一次对一个小块的字符进行动态编码，因此内存分配不会激增.

Ideally I think, the class/method I am looking for would encode the characters on the fly one small block at a time as the InputStream is being consumed, thus no big surge of mem allocation.

查看apache commons IOUtils.toInputStream(..)的源代码，我发现它还可以一次性将String转换为大字节数组.

Looking at the source code of apache commons IOUtils.toInputStream(..), I see that it also converts the String to a big byte array in one go.

并且StringBufferInputStream已过时，并且不能正确执行该工作.

And StringBufferInputStream is Deprecated, and does not do the job properly.

任何地方都有这样的util类/方法吗?还是我可以写几行代码来做到这一点?

Is there such util class/method from anywhere? Or I can just write a couple of lines of code to do this?

对此的功能需求是，在其他地方，我正在使用util方法，该方法采用InputStream并从该InputStream中流出字节.

The functional need for this is that, elsewhere, I am using a util method that takes an InputStream and stream out the bytes from this InputStream.

我似乎还没有其他人在寻找这样的东西.我在某处误东西了吗?

I haven't seem other people looking for something like this. Am I mistaking something somewhere?

我已经开始为此编写自定义类，但是如果有更好/合适/正确的解决方案/更正我的需求，它将停止.

I have started writing a custom class for this, but would stop if there is a better/proper/right solution/correction to my need.

推荐答案

Java内置库假定您只需要在输出而不是输入中将char转换为字节即可. Apache Commons IO库具有

The Java built-in libraries assume you'd only need to go from chars to bytes in output, not input. The Apache Commons IO libraries have ReaderInputStream, however, which can wrap a StringReader to get what you want.

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