RestClient ResponseSpec.body() when using Reactor Netty throws an exception instead of returning null if no response body is available

[r16turbo]

I will post again as it seems to be caused by RestClient.

Environment: Spring Web 6.1.8, Java 17

The situation is the same as in #31719, which occurs when using Reactor Netty.

Test code:
https://github.com/r16turbo/restclient-test/blob/main/src/test/java/com/example/demo/DemoApplicationTests.java
👆 Fails in the last test case (reactorNettyTest).

The reason is that the following code throws an exception:

https://github.com/spring-projects/spring-framework/blob/v6.1.8/spring-web/src/main/java/org/springframework/http/client/ReactorNettyClientResponse.java#L85

I believe that null should also be returned when using Reactor Netty, please let me know about a better way to implement this.

Example of a simple fix:
(However, Java 11 or higher is required)

	@Override
	public InputStream getBody() throws IOException {
		InputStream body = this.body;
		if (body != null) {
			return body;
		}

		body = this.connection.inbound().receive()
				.aggregate().asInputStream().block(this.readTimeout);
		if (body == null) {
			// throw new IOException("Could not receive body");
			body = InputStream.nullInputStream();  // 👈 here
		}
		this.body = body;
		return body;
	}

Thanks

[bclozel]

duplicates #32805