Make EntityModel decoratable by CodeDrivenMitch · Pull Request #4765 · AxonIQ/AxonFramework

CodeDrivenMitch · 2026-07-20T17:26:52Z

The AnnotatedEntityMetamodel is casting the EntityEvolver to an implementation; the AnnotatedEntityMetamodel. It's doing this because the AnnotatedEntityIdResolver needs access to the type information, which is an annotation-specific concern and should not be on the EntityEvolver interface.

The result was that the EntityEvolver could never be decorated, as it's impossible to satisfy the cast. This leads to the Platform client having to destruct and re-construct the EventSourcingRepository, creating very close coupling for something that should be easy.

This PR splits the annotation-specific functionality, the providing of class information about handlers, to the RepresentationResolvingEntityEvolver. Now, the EntityEvolver can be decorated, as long as decorators implement RepresentationResolvingEntityEvolver as well. The module configuration is no longer bound to an implementation, but to an interface, removing the brittle re-construct logic for Platform

The `AnnotatedEntityMetamodel` is casting the `EntityEvolver` to an implementation; the `AnnotatedEntityMetamodel`. It's doing this because the AnnotatedEntityIdResolver needs access to the type information, which is an annotation-specific concern and should not be on the EntityEvolver interface. The result was that the `EntityEvolver` could never be decorated, as it's impossible to satisfy the cast. This leads to the Platform client having to destruct and re-construct the `EventSourcingRepository`, creating very close coupling for something that should be easy. This PR splits the annotation-specific functionality, the providing of class information about handlers, to the `RepresentationResolvingEntityEvolver`. Now, the `EntityEvolver` can be decorated, as long as decorators implement `RepresentationResolvingEntityEvolver` as well. The module configuration is no longer bound to an implementation, but to an interface, removing the brittle re-construct logic for Platform

hatzlj

some small findings and one design question regarding the breaking change, but none is blocking in my opinion

hatzlj · 2026-07-21T04:59:56Z

+                return definition.createIdResolver(entityType, idType, representationResolvingEntityEvolver, c);
+            }
+            // Not possible, except when decorating, as this is a component configured by this module.
+            throw new IllegalArgumentException("The EntityMetamodel does not implement RepresentationResolvingEntityEvolver. Make sure that all decorators implement and delegate this interface.");


probably switch to AxonConfigurationException,

Suggested change

throw new IllegalArgumentException("The EntityMetamodel does not implement RepresentationResolvingEntityEvolver. Make sure that all decorators implement and delegate this interface.");

throw new AxonConfigurationException("The EntityMetamodel does not implement RepresentationResolvingEntityEvolver. Make sure that all decorators implement and delegate this interface.");

Good one, will adjust

hatzlj · 2026-07-21T05:12:14Z

+ * {@link QualifiedName}. This is useful for components that provide annotation-based usage of entities as it provides
+ * information on the wanted Java class (the representation) by the user.
+ *
+ * @param <E> The entity type this evolver applies to.


we decided to use fragment style consistently some time ago

Suggested change

* @param <E> The entity type this evolver applies to.

* @param <E> the entity type this evolver applies to

Oh wow that's a 180 form when I was in the Framework team! Will adjust

hatzlj · 2026-07-21T05:13:22Z

+     * @param qualifiedName The {@link QualifiedName} of the handler to look for.
+     * @return The {@link Class} of the expected representation for handlers of the given {@code qualifiedName}, or
+     * {@code null} if no such representation is found.
+     */


we decided to use fragment style some time ago

Suggested change

* @param qualifiedName The {@link QualifiedName} of the handler to look for.

* @return The {@link Class} of the expected representation for handlers of the given {@code qualifiedName}, or

* {@code null} if no such representation is found.

*/

* @param qualifiedName the {@link QualifiedName} of the handler to look for

* @return the {@link Class} of the expected representation for handlers of the given {@code qualifiedName}, or

* {@code null} if no such representation is found

hatzlj · 2026-07-21T05:14:58Z

-            var component = (AnnotatedEntityMetamodel<E>) c.getComponent(EntityMetamodel.class, entityName());
-            return definition.createIdResolver(entityType, idType, component, c);
+            var component = c.getComponent(EntityMetamodel.class, entityName());
+            if(component instanceof RepresentationResolvingEntityEvolver representationResolvingEntityEvolver) {


Suggested change

if(component instanceof RepresentationResolvingEntityEvolver representationResolvingEntityEvolver) {

if (component instanceof RepresentationResolvingEntityEvolver representationResolvingEntityEvolver) {

hatzlj · 2026-07-21T05:17:26Z

                                     EntityIdResolver<ID> delegate) {
        this.idType = Objects.requireNonNull(idType, "The idType should not be null.");
-        this.metamodel = Objects.requireNonNull(metamodel, "The metamodel should not be null,");
+        this.entityEvolver = Objects.requireNonNull(entityEvolver, "The entityEvolver should not be null,");


Suggested change

this.entityEvolver = Objects.requireNonNull(entityEvolver, "The entityEvolver should not be null,");

this.entityEvolver = Objects.requireNonNull(entityEvolver, "The entityEvolver should not be null.");

hatzlj · 2026-07-21T05:18:58Z

+            Configuration entityConfiguration =
+                    entityModuleConfiguration(componentRegistry.build(lifecycleRegistry), COURSE_ENTITY_NAME);
+
+            // Sanity check that the decorator actually reached the entity's (nested) EntityMetamodel component —


those em-dashes :-)

Suggested change

// Sanity check that the decorator actually reached the entity's (nested) EntityMetamodel component —

// Sanity check that the decorator actually reached the entity's (nested) EntityMetamodel component,

hjohn · 2026-07-21T10:39:49Z

I'm not fully convinced yet if we should do it like this :)

We're still accepting a plain EntityMetamodel on the messaging model builder, and IMHO, that means any EntityMetamodel should work (what's otherwise the point of interfaces). However at runtime this still fails now:

No indication during compile time that we did anything wrong
If later there is another component that needs another specific capability from the metamodel, then any decorator has to implement both...

I think we need to do either:

Somehow the builder should be honest and ask for the exact EntityMetamodel it wants, so there is no confusion and the API remains honest about what is needed. Whatever that is should be an interface so it can be decorated
Still consider just adding getExpectedReprentation to EntityMetamodel with a null default.

Any simple EntityMetamodel decorator the user now could add to the configuration would also break this; it has to also implement RepresentationResolvingEntityEvolver

smcvb · 2026-07-23T09:18:09Z

Closing this PR with the status obsolete, due to #4772 taking a different, slightly more optimized path instead.
Nonetheless, thanks for bringing this to our attention, @CodeDrivenMitch!
You can be assured that 5.3.0 will have a means to decorate the EntityMetamodel accordingly. :-)

CodeDrivenMitch self-assigned this Jul 20, 2026

CodeDrivenMitch requested a review from a team as a code owner July 20, 2026 17:26

CodeDrivenMitch requested review from hatzlj, laura-devriendt-lemon and zambrovski and removed request for a team July 20, 2026 17:26

hatzlj approved these changes Jul 21, 2026

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Review comments for decoratable entity metamodel

3b88d78

smcvb added Type: Enhancement Use to signal an issue enhances an already existing feature of the project. Priority 1: Must Highest priority. A release cannot be made if this issue isn’t resolved. labels Jul 21, 2026

smcvb added this to the Release 5.3.0 milestone Jul 21, 2026

smcvb mentioned this pull request Jul 23, 2026

Allow EntityMetamodel to be decorated without breaking ID resolution #4772

Merged

smcvb closed this Jul 23, 2026

smcvb deleted the enhancement/decoratable-entity-metamodel branch July 23, 2026 09:18

smcvb added the Status: Obsolete Use to signal this issue is no longer necessary. label Jul 23, 2026

smcvb removed this from the Release 5.3.0 milestone Jul 23, 2026

	throw new IllegalArgumentException("The EntityMetamodel does not implement RepresentationResolvingEntityEvolver. Make sure that all decorators implement and delegate this interface.");
	throw new AxonConfigurationException("The EntityMetamodel does not implement RepresentationResolvingEntityEvolver. Make sure that all decorators implement and delegate this interface.");

	* @param <E> The entity type this evolver applies to.
	* @param <E> the entity type this evolver applies to

	if(component instanceof RepresentationResolvingEntityEvolver representationResolvingEntityEvolver) {
	if (component instanceof RepresentationResolvingEntityEvolver representationResolvingEntityEvolver) {

	this.entityEvolver = Objects.requireNonNull(entityEvolver, "The entityEvolver should not be null,");
	this.entityEvolver = Objects.requireNonNull(entityEvolver, "The entityEvolver should not be null.");

	// Sanity check that the decorator actually reached the entity's (nested) EntityMetamodel component —
	// Sanity check that the decorator actually reached the entity's (nested) EntityMetamodel component,

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CodeDrivenMitch commented Jul 20, 2026

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hjohn commented Jul 21, 2026

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smcvb commented Jul 23, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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smcvb commented Jul 23, 2026 •

edited

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