EE9 Servlet API throws exceptions in normal control flow

[bjorncs]

Jetty version(s)
12.0.16

Jetty Environment
Embedded + EE9

Java version/vendor (use: java -version)
openjdk version "17.0.14" 2025-01-21 LTS
OpenJDK Runtime Environment (Red_Hat-17.0.14.0.7-1) (build 17.0.14+7-LTS)
OpenJDK 64-Bit Server VM (Red_Hat-17.0.14.0.7-1) (build 17.0.14+7-LTS, mixed mode, sharing)

OS type/version
AlmaLinux 8

Description
The method org.eclipse.jetty.ee9.nested.Request.getInputStream() attempts to write a 100 Continue interim response when invoked for the first time. If a 100 isn’t expected, the underlying HttpChannelState.ChannelResponse.writeInterim() method generates an IllegalArgumentException, which is ignored in this code path. However, this can be costly when -XX:-OmitStackTraceInFastThrow is used in production. This wasn’t the case for Jetty 11, causing a larger regression in request throughput when upgrading from 11.0 to 12.0.

Reproduce:
Send a simple HTTP/2 or HTTP/1.1 GET request without Expect: 100-continue header to Jetty using EE9 Servlet API.

[janbartel]

See PR #12789