Federico Mariani created CAMEL-24169:
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Summary: camel-jackson-avro / camel-jackson-protobuf - schema
resolver latches the first resolved schema forever, breaking multi-type routes
Key: CAMEL-24169
URL: https://issues.apache.org/jira/browse/CAMEL-24169
Project: Camel
Issue Type: Bug
Components: camel-jackson-avro
Reporter: Federico Mariani
Attachments: AvroSchemaResolverLatchesFirstSchemaIssueTest.java
*Severity:* High
*Affects:* 4.x
h3. Problem
{{AvroSchemaResolver.computeIfAbsent()}} (and the {{ProtobufSchemaResolver}}
twin) begins with {{if (this.schema != null) return this.schema;}} and ends
with {{if (answer != null) this.schema = answer;}}. So the *first* exchange
that resolves a schema permanently caches it in the instance field, and every
later exchange short-circuits to it regardless of its own body type or
per-exchange {{schema}} / {{X-Content-Class}} property. The per-type
{{schemes}} {{ConcurrentMap}} (which exists to cache per content class) becomes
dead after the first hit. The write is also unsynchronized from exchange
threads.
These resolvers are auto-discovered from the registry by
{{AbstractJacksonDataFormat.doStart()}} and shared across all routes/data
formats in the context, so a single resolver cross-contaminates different
routes.
h3. Failure scenario (reproduced)
One {{AvroSchemaResolver}}; exchange 1 resolves a {{Person}} schema (latched),
exchange 2 supplies its own {{Animal}} schema but resolves to the latched
{{Person}} schema -> marshalling with the wrong schema (Jackson-Avro error or
mis-encoded binary). Single-type kamelet usage hides it.
h3. Suggested fix
Only treat {{this.schema}} as authoritative when set explicitly via
{{setSchema(...)}} (separate field/flag); rely on the {{schemes}} map +
exchange properties for dynamic resolution; drop the trailing {{this.schema =
answer}} latch. Apply to both Avro and Protobuf resolvers.
h3. Reproducer
Attached {{AvroSchemaResolverLatchesFirstSchemaIssueTest.java}}: drives one
resolver through two exchanges carrying distinct inline schemas; exchange 2
resolves to {{Person}} (expected {{Animal}}). RED on current code.
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_Reported by Claude Code on behalf of Federico Mariani (Croway). A failing
JUnit reproducer (confirmed RED on 4.22.0-SNAPSHOT) is attached._
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