What's changed?

The ServerChan handler currently treats every HTTP 200 response as success, even when the response contains a nonzero business code or no success code. This lets a rejected or invalid response return without an AlertNoticeException.

Require a non-null response body and an explicit code == 0 before logging success. Report missing codes and nonzero codes through the existing exception path. The ServerChan FAQ documents nonzero code as an error.

Correct the existing success fixture to use code, and add regression tests using a real RestTemplate with MockRestServiceServer. These exercise JSON conversion, positive/negative business errors, empty/null/missing-code responses, malformed JSON, HTTP errors and transport failures. The HTTP responses are synthetic fixtures, not observations from a live delivery.

Only the ServerChan handler and its tests change; the shared response DTO and other channels are unchanged.

Validation

Windows, Zulu OpenJDK 25.0.4.1, Maven 3.9.16; baseline d823f2dcd52903c01d2f79b93019d379208584dc.

• Before the production fix: 13 tests, 7 failures, 0 errors, 0 skipped. The two business-error cases and five missing-success-code cases failed because no exception was thrown.
• After the fix: 13 tests, 0 failures, 0 errors, 0 skipped.
• Notification-handler regression suite (including ServerChan): 75 tests, 0 failures, 0 errors, 0 skipped.
• Maven Checkstyle passed; git diff --check passed.

mvn -B -ntp -pl hertzbeat-alerter -am -Dtest=ServerChanAlertNotifyHandlerImplTest -Dsurefire.failIfNoSpecifiedTests=false -Dmaven.test.skip=false -Djacoco.skip=true test
mvn -B -ntp -pl hertzbeat-alerter -am -Dtest=*AlertNotifyHandlerImplTest -Dsurefire.failIfNoSpecifiedTests=false -Dmaven.test.skip=false -Djacoco.skip=true test

These local runs disable coverage instrumentation; the repository POM is unchanged. Full-repository tests, packaging and live ServerChan delivery were not tested.

AI-assisted contribution

• AI assistance: Codex assisted with source inspection, regression tests, implementation, local validation and PR preparation.
• Human validation: Contributor review and personal rerun are pending. This PR is submitted as a draft for that review; automated results above were obtained by Codex.
• Risk notes: HTTP 200 responses without an explicit zero code will now fail. Custom compatible endpoints must provide the same response contract. Existing URL handling and retry behavior are unchanged.

Checklist

• Contribution and code quality guides reviewed during preparation.
• Necessary regression tests added and selected suites passed.
• Contributor personally reviewed the code and validation results.

Add or update API

Not applicable: no public API added or changed.