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== Implementation

The framework allows multiple implementations of this service to be registered; all will be called.

This is an SPI, but the framework provides a simple implementation, `o.a.i.applib.services.publishing.log.ExecutionLogger`, that just logs events as they are received.

It can be configured using:

[source,xml]
.log4j2-spring.xml
----
<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
  <Properties> ... </Properties>
  <Appenders> ... </Appenders>
  <Loggers>
    ...
    <logger
      name="org.apache.causeway.applib.services.publishing.log.ExecutionLogger"
      level="debug"/>
    ...
  </Loggers>
</Configuration>
----

See the `log4j2-spring.xml` file in xref:docs:starters:simpleapp.adoc[simpleapp] for the omitted detail.

//* the xref:mappings:outbox-publisher:about.adoc[Outbox Publisher] in the xref:mappings:ROOT:about.adoc[Mappings catalog] persists each interaction into a link:https://microservices.io/patterns/data/transactional-outbox.html[outbox table] for subsequent processing.
