intellij-sdk-code-samples/basics/plugin_structure/plugin_components.md

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Plugin Components

Warning

When writing new plugins, creating components should be avoided. Any existing components should be migrated to services, extensions, or listeners (see below).

Plugin components are a legacy feature supported for compatibility with plugins created for older versions of the IntelliJ Platform. Plugins using components do not support dynamic loading (the ability to install, update, and uninstall plugins without restarting the IDE).

Plugin components are defined in the <application-components>, <project-components>, and <module-components> sections in a Plugin Configuration File.

Migration

To migrate existing code from components to more modern APIs, please see the following guidelines.

Manage State

To manage some state or logic that is only needed when the user performs a specific operation, use a Service.

Persisting State

To store the state of your plugin at the application or project level, use a Service, and implement the PersistentStateComponent interface. See Persisting State of Components for details.

Subscribing to Events

To subscribe to events, use a listener or create an extension for a dedicated extension point (for example, com.intellij.editorFactoryListener) if one exists for the event to subscribe to.

Application Startup

Executing code on application startup should be avoided whenever possible because it slows down startup. Plugin code should only be executed when projects are opened (see Project Open) or when the user invokes an action of a plugin. If this cannot be avoided, add a listener subscribing to the AppLifecycleListener topic.

Project Open

To execute code when a project is being opened, use one of these two extensions:

• StartupActivity registered via com.intellij.postStartupActivity for immediate execution
• StartupActivity.Background registered via com.intellij.backgroundPostStartupActivity for execution with 5 seconds delay (2019.3 or later)

Application/Project Close

To execute code on project closing or application shutdown, implement the Disposable interface in a Service and place the code in the dispose() method. Alternatively, use Disposer.register() passing a Project or Application service instance as the parent argument (see Choosing a Disposable Parent).