Attribute is required but not set (Unable to create snapshot class for interface)

My Liferay 7 server was using SomeModule happily, until I deployed a new version of SomeModule which has an additional required field favoriteColor.

Now whenever I try to load the portlet Liferay says:

java.lang.RuntimeException: Unable to create snapshot class for interface some.SomeModuleConfiguration
        at com.liferay.portal.configuration.metatype.bnd.util.ConfigurableUtil._createConfigurableSnapshot(ConfigurableUtil.java:77)
        at com.liferay.portal.configuration.metatype.bnd.util.ConfigurableUtil.createConfigurable(ConfigurableUtil.java:51)
        at some.SomeModule.activate(SomeModule.java:50)
...
aused by: java.lang.IllegalStateException: Attribute is required but not set favoriteColor
        at aQute.bnd.annotation.metatype.Configurable$ConfigurableHandler.invoke(Configurable.java:75)
        at com.sun.proxy.$Proxy1220.favoriteColor(Unknown Source)
        at some.SomeModuleConfigurationSnapshot407.<init>(Unknown Source)

The configuration UI for SomeModule does not show anything about favoriteColor.

How to fix that, for instance by setting favoriteColor to its default value?

Solution

An alternative path would be using a OSGi configuration file to set defaults and missing values. You can use those files as you do for those modules that come with liferay; e.g., elasticsearch config. (check your osgi/configs directory)