Causeway

= Apache Causeway :toc: :toc-title: pass:[<h3>Contents</h3>] :toc-placement!:

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https://causeway.apache.org[Apache Causeway] software is a framework for rapidly developing domain-driven apps in Java. Write your business logic in entities, domain services and repositories, and the framework dynamically generates a representation of that domain model as a webapp or a RESTful API.

Start learning about Apache Causeway using the https://github.com/apache/causeway-app-helloworld["Hello World"] starter app. //TODO update: Explore features with our daily built demo docker image https://github.com/apache/causeway/blob/master/examples/demo/domain/src/main/adoc/modules/demo/pages/about.adoc["DemoApp"]. Build your own apps using our https://github.com/apache/causeway-app-simpleapp["SimpleApp"] starter app.

For help and support, join our https://causeway.apache.org/docs/2.0.0-M9/support/slack-channel.html[Slack channel] or https://causeway.apache.org/docs/2.0.0-M7/support/mailing-list.html[mailing list].

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== Core Features

Apache Causeway automatically generates the UI from the domain classes.

=== Sign-in

Apache Causeway integrates with link:https://spring.io/projects/spring-security[Spring Security] and link:https://www.keycloak.org/[Keycloak] for authentication concerns, typically in combination with OAuth2. These are usually combined with the SecMan module, which provides a set of domain entities that model an authenticaiton model: users, roles and permissions against features derived from the Apache Causeway metamodel. The SecMan user is mapped to the authentical principle provided by Spring or Keycloak. Alternatively, SecMan can perform its own local authentication.

image::https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/010-login.png[link="https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/010-login.png"]

=== Install Fixtures

Apache Causeway has lots of features to help you prototype and then fully test your application. One such are fixture scripts, which allow pre-canned data to be installed in the running application. This is great to act as the starting point for identifying new stories; later on when the feature is being implemented, the same fixture script can be re-used within that feature's integration tests. (More on tests later).

image::https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/020-install-fixtures.png[link="https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/020-install-fixtures.png"]

=== Dashboard and View Models

Most of the time the end-user interacts with representations of persistent domain entities, but Causeway also supports view models which can aggregate data from multiple sources. The todoapp example uses a "dashboard" view model to list todo items not yet done vs those completed.

image::https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/030-dashboard-view-model.png[link="https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/030-dashboard-view-model.png"]

In general we recommend to initially focus only on domain entities; this will help drive out a good domain model. Later on view models can be introduced in support of specific use cases.

=== Domain Entity

The screenshot below is of the todoapp's ToDoItem domain entity. Like all web pages, this UI is generated at runtime, directly from the domain object itself. There are no controllers or HTML to write.

image::https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/040-domain-entity.png[link="https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/"]

In addition to the domain entity, Apache Causeway allows layout metadata hints to be provided, for example to specify the grouping of properties, the positioning of those groups into columns, the association of actions (the buttons) with properties or collections, the icons on the buttons, and so on. This metadata can be specified either as annotations or in JSON form; the benefit of the latter is that it can be updated (and the UI redrawn) without restarting the app.

Any production-ready app will require this metadata but (like the view models discussed above) this metadata can be added gradually on top of the core domain model.

=== Edit properties

By default properties on domain entities are editable, meaning they can be changed directly. In the todoapp example, the ToDoItem's description is one such editable property:

image::https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/050-edit-property.png[link="https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/050-edit-property.png"]

Note that some of the properties are read-only even in edit mode; individual properties can be made non-editable. It is also possible to make all properties disabled and thus enforce changes only through actions (below).

=== Actions

The other way to modify an entity is to an invoke an action. In the screenshot below the ToDoItem's category and subcategory can be updated together using an action:

image::https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/060-invoke-action.png[link="https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/060-invoke-action.png"]

There are no limitations on what an action can do; it might just update a single object, it could update multiple objects. Or, it might not update any objects at all, but could instead perform some other activity, such as sending out email or printing a document.

In general though, all actions are associated with some object, and are (at least initially) also implemented by that object: good old-fashioned encapsulation. We sometimes use the term "behaviourally complete" for such domain objects.

=== Mixins

As an alternative to placing actions (business logic) on a domain object, it can instead be placed inside a mixin object. When an object is rendered by Apache Causeway, the mixin "contributes" its behaviour to the domain object (similar to aspect-oriented traits).

In the screenshot below the highlighted "export as xml" action, the "relative priority" property (and "previous" and "next" actions) the "similar to" collection and the two "as DTO" actions are all contributed by mixins:

image::https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/065-contributions.png[link="https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/065-contributions.png"]

The code snippet below shows how this works for the "as DTO v1.0" action:

image::https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/067-contributed-action.png[link="https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/067-contributed-action.png"]

== Extensible Views

The Apache Causeway viewer is implemented using http://wicket.apache.org[Apache Wicket], and has been architected to be extensible. For example, when a collection of objects is rendered, this is just one several views, as shown in the selector drop-down:

image::https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/070-pluggable-views.png[link="https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/070-pluggable-views.png"]

// The gmap3 extension will render any domain entity (such as ToDoItem) that implements its Locatable interface: // // image::https://raw.githubusercontent.com/apache/causeway/master/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/080-gmap3-view.png[link="https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/080-gmap3-view.png"]

Thus, the fullcalendar2 extension will render any domain entity (such as ToDoItem) that implements its Calendarable interface:

image::https://raw.githubusercontent.com/apache/causeway/main/antora/components/docs/modules/ROOT/images/what-is-apache-causeway/causeway-in-pictures/090-fullcalendar2-view.png[link="https://raw.