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89 lines
5.0 KiB
Markdown
89 lines
5.0 KiB
Markdown
---
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title: Plugin Extensions
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redirect_from:
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/basics/plugin_structure/plugin_extensions_and_extension_points.html
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---
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_Extensions_ are the most common way for a plugin to extend the functionality of the IntelliJ Platform in a way
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that is not as straightforward as adding an action to a menu or toolbar. The following are some of the most common
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tasks accomplished using extensions:
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* The `com.intellij.toolWindow` extension point allows plugins to add [tool windows](/user_interface_components/tool_windows.md)
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(panels displayed at the sides of the IDE user interface);
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* The `com.intellij.applicationConfigurable` and `com.intellij.projectConfigurable` extension points allow plugins to add pages to the
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Settings/Preferences dialog;
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* [Custom language plugins](/reference_guide/custom_language_support.md) use many extension points
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to extend various language support features in the IDE.
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There are [more than 1000 extension](#how-to-get-the-extension-points-list) points available in the platform and the bundled plugins, allowing to customize
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different parts of the IDE behavior.
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## Declaring Extensions
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> **TIP** Auto-completion is available for all these steps.
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1. Add an `<extensions>` element to your plugin.xml if it's not yet present there. Set the `defaultExtensionNs` attribute to one of the following values:
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* `com.intellij`, if your plugin extends the IntelliJ Platform core functionality.
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* `{ID of a plugin}`, if your plugin extends a functionality of another plugin.
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2. Add a new child element to the `<extensions>` element. The child element name must match the name of the extension point you want the extension to access.
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3. Depending on the type of the extension point, do one of the following:
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* If the extension point was declared using the `interface` attribute, for newly added child element, set the `implementation` attribute to the name of the class that implements the specified interface.
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* If the extension point was declared using the `beanClass` attribute, for newly added child element, set all attributes annotated with the [`@Attribute`](upsource:///platform/util/src/com/intellij/util/xmlb/annotations/Attribute.java) annotations in the specified bean class.
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To clarify this procedure, consider the following sample section of the `plugin.xml` file that defines two extensions designed to access the `com.intellij.appStarter` and `com.intellij.projectTemplatesFactory` extension points in the *IntelliJ Platform* and one extension to access the `another.plugin.myExtensionPoint` extension point in another plugin `another.plugin`:
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```xml
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<!-- Declare extensions to access extension points in the IntelliJ Platform.
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These extension points have been declared using "interface".
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-->
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<extensions defaultExtensionNs="com.intellij">
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<appStarter implementation="com.myplugin.MyAppStarter" />
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<projectTemplatesFactory implementation="com.myplugin.MyProjectTemplatesFactory" />
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</extensions>
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<!-- Declare extensions to access extension points in a custom plugin "another.plugin"
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The "myExtensionPoint" extension point has been declared using "beanClass"
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and exposes custom properties "key" and "implementationClass".
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-->
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<extensions defaultExtensionNs="another.plugin">
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<myExtensionPoint key="keyValue" implementationClass="com.myplugin.MyExtensionPointImpl" />
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</extensions>
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```
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### Extension default properties
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The following properties are available always:
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- `id` - unique ID
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- `order` - allows to order all defined extensions using `first`, `last` or `before|after [id]` respectively
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- `os` - allows to restrict extension to given OS, e.g., `os="windows"` registers the extension on Windows only
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### Extension properties code insight
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Several tooling features are available to help configuring bean class extension points in `plugin.xml`.
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Property names matching the following list will resolve to FQN:
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- `implementation`
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- `className`
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- `serviceInterface` / `serviceImplementation`
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- ending with `Class` (case-sensitive)
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A required parent type can be specified in the extension point declaration via nested `<with>`:
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```xml
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<extensionPoint name="myExtension" beanClass="MyExtensionBean">
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<with attribute="psiElementClass" implements="com.intellij.psi.PsiElement"/>
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</extensionPoint>
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```
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Property name `language` will automatically resolve to all present `Language` IDs.
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Specifying `@org.jetbrains.annotations.Nls` verifies capitalization of UI text properties according to given `capitalization` value (2019.2 and later).
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## How to get the extension points list?
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To get a list of extension points available in the *IntelliJ Platform* core, consult the `<extensionPoints>` section of the following XML configuration files:
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* [`LangExtensionPoints.xml`](upsource:///platform/platform-resources/src/META-INF/LangExtensionPoints.xml)
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* [`PlatformExtensionPoints.xml`](upsource:///platform/platform-resources/src/META-INF/PlatformExtensionPoints.xml)
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* [`VcsExtensionPoints.xml`](upsource:///platform/platform-resources/src/META-INF/VcsExtensionPoints.xml)
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