Intellij Plugin: Cannot init component state exception

I am trying to create an Intellij Idea Plugin with some configurations in Settings->Tools.

I have an ApplicationService to hold and save those configurations, but an exception occurs when calling ServiceManager.getService(MyService.class), and the configuration don't persist upon reopening Intellij Idea.

Here is the stack trace for the exception:

com.intellij.diagnostic.PluginException: Cannot init  component state [Plugin: org.mycompany.mycompany-plugin]
	at com.intellij.configurationStore.ComponentStoreImpl.initComponent(ComponentStoreImpl.kt:116)
	at com.intellij.configurationStore.ComponentStoreWithExtraComponents.initComponent(ComponentStoreWithExtraComponents.kt:50)
	at com.intellij.serviceContainer.ComponentManagerImpl.initializeComponent$intellij_platform_serviceContainer(ComponentManagerImpl.kt:358)
	at com.intellij.serviceContainer.ServiceComponentAdapter.createAndInitialize(ServiceComponentAdapter.kt:58)
	at com.intellij.serviceContainer.ServiceComponentAdapter.doCreateInstance(ServiceComponentAdapter.kt:41)
	at com.intellij.serviceContainer.BaseComponentAdapter.getInstanceUncached(BaseComponentAdapter.kt:115)
	at com.intellij.serviceContainer.BaseComponentAdapter.getInstance(BaseComponentAdapter.kt:69)
	at com.intellij.serviceContainer.ComponentManagerImpl.doGetService(ComponentManagerImpl.kt:411)
	at com.intellij.serviceContainer.ComponentManagerImpl.getService(ComponentManagerImpl.kt:394)
	at com.intellij.openapi.components.ServiceManager.getService(ServiceManager.java:20)
	at com.mycompany.config.SettingsService.getInstance(SettingsService.java:14)
	at com.mycompany.config.SettingsConfigurable.reset(SettingsConfigurable.java:46)
	at com.intellij.openapi.options.ex.ConfigurableWrapper.reset(ConfigurableWrapper.java:177)
	at com.intellij.openapi.options.ex.ConfigurableCardPanel.reset(ConfigurableCardPanel.java:166)
	at com.intellij.openapi.options.ex.ConfigurableCardPanel.lambda$createConfigurableComponent$4(ConfigurableCardPanel.java:118)
	at com.intellij.openapi.application.impl.ApplicationImpl.runReadAction(ApplicationImpl.java:894)
	(a lot more lines here)
Caused by: java.lang.UnsupportedOperationException: configurationSchemaKey must be specified for com.mycompany.config.SettingsService
	at com.intellij.configurationStore.ComponentStoreImpl.initComponent(ComponentStoreImpl.kt:369)
	at com.intellij.configurationStore.ComponentStoreImpl.initComponent(ComponentStoreImpl.kt:100)
	... 113 more

I found no documentation about that "configurationSchemaKey", except for the fact that it's an ApplicationService XML paramter - but I could not find out what value I should put in it. I.

Here's how I defined the service:

<applicationService
                serviceImplementation="com.testmycode.config.SettingsService"
                id="com.testmycode.config.SettingsService"/>

What am I missing?

configurationSchemaKey property is a part of the ServiceDescriptor and is described as:

> Cannot be specified as part of {@link State} because to get annotation, class must be loaded, but it cannot be done for performance reasons.

However, it's not common to create such a service for handling settings.

Please review your current implementation and follow the Introduction to Settings guide in the IntelliJ Platform SDK DevGuide.