aglinxinyuan opened a new issue, #5042:
URL: https://github.com/apache/texera/issues/5042
### Root cause
`amber/src/main/scala/org/apache/texera/workflow/LogicalLink.scala` declares
only a *single* `@JsonCreator` overload that accepts raw `String` op-ids:
```scala
@JsonCreator
def this(
@JsonProperty("fromOpId") fromOpId: String,
fromPortId: PortIdentity,
@JsonProperty("toOpId") toOpId: String,
toPortId: PortIdentity
) = this(OperatorIdentity(fromOpId), fromPortId, OperatorIdentity(toOpId),
toPortId)
```
But `objectMapper.writeValueAsString` serializes `OperatorIdentity` as an
*object* `{"id": "op-A"}` (its scalapb case-class shape), not as a raw string.
Jackson dispatches deserialization to the only `@JsonCreator` it knows — the
String overload — which then rejects the object value.
### Reproduce
```scala
val original = LogicalLink(
OperatorIdentity("op-A"), PortIdentity(0),
OperatorIdentity("op-B"), PortIdentity(1)
)
val json = objectMapper.writeValueAsString(original)
// json = {"fromOpId":{"id":"op-A"}, "fromPortId":...,
"toOpId":{"id":"op-B"}, "toPortId":...}
objectMapper.readValue(json, classOf[LogicalLink])
// throws com.fasterxml.jackson.databind.exc.MismatchedInputException:
// Cannot deserialize value of type `java.lang.String` from Object value
```
The current characterization is pinned in
[`LogicalLinkSpec`](https://github.com/apache/texera/blob/main/amber/src/test/scala/org/apache/texera/workflow/LogicalLinkSpec.scala)
("NOT round-trip through writeValueAsString …") so the asymmetry can't drift
silently.
### Surface
| Surface | Write → Read |
| --- | --- |
| Frontend-saved workflow JSON (`fromOpId: "op-A"`, string form) | works —
String overload dispatched |
| `objectMapper.writeValueAsString(link)` → `objectMapper.readValue(json,
classOf[LogicalLink])` (object form) | **broken** — String overload rejects the
object value |
### Before → after
| | Before | After |
| --- | --- | --- |
| `treeToValue` from string-shaped JSON | ✅ | ✅ (unchanged) |
| `writeValueAsString` → `readValue` round-trip | ❌
`MismatchedInputException` | ✅ |
| Characterization test in `LogicalLinkSpec` | pinned asymmetry | needs to
flip to a passing round-trip assertion alongside the fix |
### Proposed fix (pick one)
1. Add a second `@JsonCreator` overload that accepts an object-shape
`OperatorIdentity`, OR
2. Annotate `fromOpId` / `toOpId` with a custom `@JsonDeserialize` that
handles both shapes (string and `{"id": ...}`).
### Tracked by
The asymmetry is currently characterized (not asserted as passing) in
`LogicalLinkSpec` — see review thread in PR #4956. When the fix lands, that
test must be flipped to assert a successful round-trip.
### Priority
P3 - Low (no production data loss; serialization-path-only)
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