Package io.fluxcapacitor.javaclient.modeling

Annotation Interface Member

@Documented
@Target({FIELD,METHOD})
@Retention(RUNTIME)
@Inherited
public @interface Member

Indicates that the annotated field or getter represents a nested entity or collection of entities within an aggregate.

Entities marked with @Member participate in aggregate routing, event sourcing, and update application. When an update targets a nested entity, Flux will use this annotation to traverse the aggregate structure and locate the correct entity (or entities) to apply the update to.

This annotation supports modeling complex aggregates composed of multiple entities, for example:

 @Aggregate
 public class Project {
     @EntityId
     String projectId;

     @Member
     List<Task> tasks;
 }
 

Here, updates targeting Task entities will automatically be routed by matching TaskId (declared with EntityId) inside the Task class.

Support for new entities

If no matching entity is found for a given update, Flux will still evaluate the update against applicable @Apply and @AssertLegal methods. This allows new entity creation directly from the update payload when appropriate logic is defined.
For example:

 @Apply
 Task create() {
     return Task.builder().taskId(taskId).details(taskDetails).build();
 }
 

will be used to create a new Task if no matching task exists in the tasks member list.

Immutability and parent updates

Flux assumes immutability by default. When a nested entity is added, removed, or modified, Flux will attempt to create a new version of the parent entity by copying and updating the annotated container field (list, map, etc.). The parent is not modified directly.
This behavior ensures safe update propagation and accurate change tracking, especially during event sourcing.
For example, if ProductCategory has a list of Products:

 @Member
 List<Product> products;
 

and one product is updated, Flux will replace the products list with a new list containing the updated entity.

Optional attributes

• idProperty (default: empty):
  Use this to explicitly specify the identifier property name on the nested entity. By default, Flux locates the identifier via the EntityId annotation.
• wither (default: empty):
  Defines a method (by name) that should be invoked to update the container when the entity is added, removed, or replaced. Normally, Flux will update the container (e.g., list or map) automatically. This setting is useful for immutable containers or cases requiring side effects during updates.

Supported container types:

• Single nested entities (e.g., Product product)
• Collections of entities (e.g., List<Product>)
• Maps of entities keyed by their identifier

See Also:

• EntityId
• Aggregate
• Apply
• AssertLegal

Optional Element Summary

Optional Elements

Modifier and Type	Optional Element	Description
String	idProperty	Specifies the name of the identifier property on the nested entity, if different from the default detected one.
String	wither	Optionally defines the name of a method that should be used to apply updates to the container of the nested entity.

Element Details

idProperty

String idProperty

Specifies the name of the identifier property on the nested entity, if different from the default detected one.

Default:

""

wither

String wither

Optionally defines the name of a method that should be used to apply updates to the container of the nested entity.

Normally, Flux automatically updates the container (for lists, maps, or singletons). This attribute is only necessary if a custom update method must be invoked instead.

Default:

""