[ISSUE #8321] Fail fast when shenyu.httpclient.strategy holds an unsupported value - #8341

Fixes #8321.

Problem

shenyu.httpclient.strategy accepts netty and webClient. Any other value — web-client, web_client, an empty value, or a value with surrounding whitespace — leaves the gateway in a state where it starts successfully but has no HTTP client plugin at all, and every proxied request fails without any startup hint pointing at the misconfiguration.

The two built-in HTTP plugins are selected by mutually exclusive conditional configuration classes in HttpClientPluginConfiguration:

• NettyHttpClientConfiguration — @ConditionalOnProperty(name = "shenyu.httpclient.strategy", havingValue = "netty", matchIfMissing = true)
• WebClientConfiguration — @ConditionalOnProperty(name = "shenyu.httpclient.strategy", havingValue = "webClient")

matchIfMissing = true only covers the case where the property is absent. When the property is present but does not match either condition, neither plugin bean is registered. The gateway then starts, the plugin chain has no http client node, divide routes never reach an upstream, and with the response plugin enabled ResponsePlugin finds no HTTP message writer and fails the request with a NullPointerException. Nothing in the startup log points at the strategy value, and HttpClientProperties.getStrategy() performed no validation either.

An empty value is the same failure: matchIfMissing does not apply to a property that is present, so an empty or valueless entry matches neither condition.

Root cause

Plugin selection was driven by property conditions while the configured value itself was never validated, so an unsupported value was silently equivalent to "no http client plugin at all". The validation also has to stay compatible with the way the conditions match: @ConditionalOnProperty compares the configured value with String#equalsIgnoreCase, so NETTY, webclient and WebClient are legal today and must keep working.

Change

• HttpClientProperties documents the legal values on the strategy property and exposes them as the NETTY_STRATEGY and WEB_CLIENT_STRATEGY constants.
• HttpClientProperties implements InitializingBean and validates the bound value in afterPropertiesSet(), that is once the container has bound the properties and before the gateway serves any traffic. An unsupported value fails the application context with Invalid value 'web-client' for property 'shenyu.httpclient.strategy', supported values are 'netty' and 'webClient'.
• A property that is present but has no value is rejected as well. The binder skips such a property, so the bound value alone cannot tell an absent property from a valueless one; HttpClientProperties therefore also implements EnvironmentAware and uses Environment#containsProperty on the same key the conditions read, which distinguishes the two cases exactly.
• The check accepts exactly what the plugin selection conditions accept: netty and webClient, matched case-insensitively, with an absent property still falling back to the netty strategy. Values are neither trimmed nor rewritten, because the conditions do not trim either.
• RELEASE-NOTES.md documents the behavior change.

Tests

• HttpClientPropertiesTest: unsupported values (web-client, web_client, empty, blank padded, httpclient) are rejected with a message naming the property and both legal values; netty, webClient and their case variants are accepted; an absent value is accepted; a configured but valueless property is rejected while an absent one is accepted; afterPropertiesSet() rejects an unsupported value.
• HttpClientPluginConfigurationTest: the application context now fails to start for web-client, for an empty value and for a valueless property, while netty, webClient, NETTY, webclient and an absent property still register the corresponding plugin.

Red and green: with the new tests in place and the production change reverted, the startup tests fail because the context starts successfully instead of failing; with the production change in place the whole module is green.

Verification

• shenyu-plugin-httpclient: 169 tests, 0 failures (163 before plus 6 new).
• shenyu-spring-boot-starter-plugin-httpclient: 27 tests, 0 failures (21 before plus 6 new).
• shenyu-plugin-response 17 and shenyu-spring-boot-starter-plugin-response 3 are unchanged, so the response plugin selection is not affected.
• Full reactor build of the touched modules: BUILD SUCCESS.
• checkstyle:check for both changed modules: 0 violations.

Scope note

ResponsePluginConfiguration selects the HTTP message writer from the same property with the same pair of conditions. This change does not touch it: the gateway starter always ships the http client starter, so an unsupported value now fails the gateway startup before the writer selection can matter. A deployment that uses the response starter without the http client starter is not covered here.

4 files changed, 235 insertions(+), 4 deletions(-)