docs/asciidoc/cayenne-guide/src/docs/asciidoc/_cayenne-guide/part5/commitLog.adoc

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include::../var.adoc[]

[[ext-commit-log]]
=== Commit log extension

The goal of this module is to capture commit changes and present them to interested parties in an easy-to-process format.

==== Maven

[source, XML,subs="verbatim,attributes"]
----
<dependency>
    <groupId>org.apache.cayenne</groupId>
    <artifactId>cayenne-commitlog</artifactId>
    <version>{version}</version>
</dependency>
----

==== Gradle

[source, Groovy,subs="verbatim,attributes"]
----
compile 'org.apache.cayenne:cayenne-commitlog:{version}'
----

==== Usage

In order to use `commitlog` module you need to perform three steps:

. Mark all entities which changes you are interested in with `@org.apache.cayenne.commitlog.CommitLog` annotation
+
[source, Java]
----
@CommitLog(ignoredProperties = {"somePrivatePropertyToSkip"})
public class MyEntity extends _MyEntity {
    // ...
}
----

. Implement `CommitLogListener` interface.
+
[source, java]
----
public class MyCommitLogListener implements CommitLogListener {
    @Override
    public void onPostCommit(ObjectContext originatingContext, ChangeMap changes) {
        // ChangeMap will contain all information about changes happened in performed commit
        // this particular example will print IDs of all inserted objects
        changes.getUniqueChanges().stream()
            .filter(change -> change.getType() == ObjectChangeType.INSERT)
            .map(ObjectChange::getPostCommitId)
            .forEach(id -> System.out.println("Inserted new entity with id: " + id));
    }
}
----

. Register your listener implementation.
+
[source, java]
----
ServerRuntime.builder()
        .addModule(CommitLogModule.extend()
                .addListener(MyCommitLogListener.class)
                .module())
----
+
NOTE: You can use several listeners, but they all will get same changes.