[jira] [Commented] (SAMZA-1160) Migrate MapConfig inherited Java classes to use composition over inheritance

["Yi Pan (Data Infrastructure) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SAMZA-1160?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16312132#comment-16312132 ] 

Yi Pan (Data Infrastructure) commented on SAMZA-1160:
-----------------------------------------------------

[~fji], thanks for bringing up this point. +1 on the overall idea to change it to composition rather then inheritance. The only additional point is that we would need to be careful about public config classes in samza-api for backward compatibility verification.

> Migrate MapConfig inherited Java classes to use composition over inheritance
> ----------------------------------------------------------------------------
>
>                 Key: SAMZA-1160
>                 URL: https://issues.apache.org/jira/browse/SAMZA-1160
>             Project: Samza
>          Issue Type: Task
>            Reporter: Fred Ji
>            Assignee: Fred Ji
>             Fix For: 0.15.0
>
>
> In Samza code, we have a lot of classes with the name "*Config" which inherits from MapConfig but only intending to exposing the APIs for the specific configuration.
> For example, JavaStorageConfig, it currently extends MapConfig, but it only intends to manage/fetch storeNames and store related configs, but not other configs. With the inheritance, it does not have good encapsulation and it allows the object JavaStorageConfig to call any public API from MapConfig as well, for example, javaStorageConfig.get("yarn.resources.package.path"). With it, it mixes up the business logic for different types of Config.
> A proposal for addressing this is to do composition over inheritance, each type of Config, for example, JavaStorageConfig can have a member variable config which can leverage the interface of Config class (or the implementation of MapConfig) but not exposing the APIs of Config further down. 



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