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@Idempotent

Every attribute of the annotation, its default, and which are rejected on an HTTP endpoint.

@Idempotent(
    key = "#event.id()",        // SpEL over the method's parameters. Required here
    scope = "",                 // Empty: <simple class name>.<method name>
    ttl = "PT24H",              // How long the record stays replayable (ISO-8601)
    lease = "PT30S",            // How long this acquisition is protected
    waitTimeout = "PT10S",      // How long a concurrent caller blocks. "PT0S" to not block
    completion = "",            // autonomous | join-transaction
    codec = ""                  // PayloadCodec bean name, for a method that returns a value
)
Java

Attributes

Attribute Default when empty Notes
key - SpEL over the method’s parameters. Required on a method; rejected on an endpoint
scope <simple class name>.<method name> See scope and key
ttl idempotency.default-ttl ISO-8601 duration
lease idempotency.default-lease ISO-8601 duration
waitTimeout idempotency.default-wait ISO-8601 duration. PT0S to not block
completion idempotency.completion-mode autonomous or join-transaction. Rejected on an endpoint
codec - PayloadCodec bean name. Required on a value-returning method, rejected on a void one and on an endpoint

Every attribute except key, scope and codec takes the application default from configuration when left empty.

Rejected on an endpoint, and why

Three attributes are rejected at startup on a request mapping handler:

Attribute Why
key An HTTP request brings its own key in the header. A second key from the annotation would mean two identities for one call
codec The filter stores the HTTP response through its own StoredResponseCodec
completion The filter completes after the response is captured, outside any method transaction

Validation

Anything malformed - an unparseable duration, an unknown completion mode, an over-long scope, a value-returning method with no codec, a void method with one - is rejected when the context starts, not on the first message.

Behaviour on a void method

There is nothing to replay, so codec must be empty. A duplicate returns without running the method. The outcome still distinguishes Executed from Replayed for a lifecycle listener that cares.