Cannot close custom OutputStream

[brucelwl]

I use CustomServletServerHttpResponse to inherit ServletServerHttpResponse and customize the compression algorithm for response requests. However, I found that my close method cannot be called due to the following code Unable to clear CustomOutputStream native memory,

spring-framework/spring-web/src/main/java/org/springframework/http/converter/json/AbstractJackson2HttpMessageConverter.java

Lines 452 to 456 in 6d97791

	OutputStream outputStream = StreamUtils.nonClosing(outputMessage.getBody());
	try (JsonGenerator generator = objectMapper.getFactory().createGenerator(outputStream, encoding)) {
	writePrefix(generator, object);

I have searched for relevant issues, but I have not found a clear solution to close my own defined OutputStream

[brucelwl]

Using java.lang.ref.Cleaner in Java 9 seems to be a good solution ?

  @Override
    public OutputStream getBody() throws IOException {
        if (customOutputStream == null) {
            OutputStream body = super.getBody();
            customOutputStream = new CustomOutputStream(body);
            cleanable = cleaner.register(this, new CustomOutputStreamClear(customOutputStream));
        }
        return customOutputStream;
    }

[rstoyanchev]

There is not enough detail about what applies the response wrapper, and what needs to be done to be able to advise. We have filters like ShallowEtagHeaderFilter that apply a wrapper and then handle it after the return from the filter chain.

Generally, message converters are neutral to how they are used, and make no assumptions about when the response should be closed.

Closing for now as this is by design, but feel free to comment further.