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Version: v11.*.*

Audit, History & Event-Management

Kadai allows auditing every change regarding Tasks, Workbaskets and Classifications. This is implemented via a custom event-management-system.

All components are fully synchronous and therefore blocking.

Below we will go through the core concepts and how to register custom Event-Listeners via SPIs.

Core-Concepts​

Here is an overview about all the central components in Kadai's event-management.

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KadaiInitializable and Reifiable​

KadaiInitializable is a helper-interface giving access to the KadaiEngine. It can be used in non-bean KadaiEventConsumers to interact with the KadaiEngine. Reifiable is a helper-interface aiding in type-safety for event-routing in the KadaiEventBus. Its implementation is trivial as Java's type-system only allows returning this implementing class.

KadaiEvent​

KadaiEvent is the common and most high-level interface for all Kadai-Events.

KadaiEventConsumer​

KadaiEventConsumer is a sink for certain KadaiEvents. It's consumed events can be specified via the type-arg. The KadaiEventBus will then only route events of this type or those extending it to that consumer.

KadaiEventPublisher​

A mediator between producer and broker. The default implementation SimpleKadaiEventPublisher forwards the event to the broker. It's used to scope access to publishing events inside producers.

KadaiEventBus​

KadaiEventBus manages event-producers and -consumers. It takes care of routing events to all eligible consumers and enriching them with user-context. When constructed, it reads all consumers declared via SPI. At runtime, more consumers can be registered via the Java-API.

Concrete Example for Task​

Task-Producer & -Publisher​

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Task-Event & -Consumer​

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Registering custom Consumers​

Custom consumers are plain Java-Classes implementing KadaiEventConsumer<T> for a specific T extending KadaiEvent.

Here is the task-consumer from earlier (it's also just a class loaded via SPI):

src/main/java/META-INF.services/io.kadai.simplehistory.task.internal.TaskHistoryEventPersister
package io.kadai.simplehistory.task.internal;

import io.kadai.common.api.KadaiEngine;
import io.kadai.spi.history.api.KadaiEventConsumer;
import io.kadai.spi.history.api.events.task.TaskHistoryEvent;

public class TaskHistoryEventPersister implements KadaiEventConsumer<TaskHistoryEvent> {

  private TaskHistoryServiceImpl taskHistoryService;

  // Actual consumer-logic
  @Override
  public void consume(TaskHistoryEvent event) {
    taskHistoryService.createTaskHistoryEvent(event);
  }

  // Java-Boilerplate aiding in type-safety for event-routing
  @Override
  public Class<TaskHistoryEvent> reify() {
    return TaskHistoryEvent.class;
  }

  // Helper allowing access to the KadaiEngine
  @Override
  public void initialize(KadaiEngine kadaiEngine) {
    this.taskHistoryService = new TaskHistoryServiceImpl();
    taskHistoryService.initialize(kadaiEngine);
  }
}

Now place the fully-qualified class-name of your custom consumer into the meta-inf services-file for the interface:

resources/META-INF.services/io.kadai.spi.history.api.KadaiEventConsumer
io.kadai.simplehistory.task.internal.TaskHistoryEventPersister
# your custom consumers ...

For more information on Java-SPIs check out our SPI-Guide.