Skip buffer allocation in StreamUtils.copy(String)

[7fantasy7]

Writer writer = new OutputStreamWriter(out, charset); writer.write(in); writer.flush();

OutputStreamWriter constuctor does unnecessary buffer allocation (8kb)

Given that it already has a string, maybe it can be avoided writing a string to the stream directly.

out.write(in.getBytes(charset)); out.flush();

It's used in plaintext endpoints through StringHttpMessageConverter

Here's approximate difference in time

| String Length | copy (ns/op) | copyOSW (ns/op) | | ------------- | ------------ | --------------- | | 10 | 4.314 | 311.848 | | 100 | 9.187 | 310.556 | | 1,000 | 35.274 | 569.202 | | 10,000 | 545.262 | 1581.522 | | 50,000 | 1833.014 | 6171.236 | | 100,000 | 3341.869 | 11976.815 | 

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