Create builder with mandatory fields.

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ololoshka

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Dec 6, 2021, 4:36:16 PM12/6/21
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Create builder with mandatory fields. Without builder you can make
certain fields be mandatory initiated using constructor only. 
Current builder doesn't provide initialization validation but it can be created.
Here I attach ugly first solution that came on my mind:
In this example you are obliged to initialize user name and user age when
you build it. Otherwise you just can't call builder method. 
I believe that such builder will increase code quality. 
Thanks and best regards. 

Jan Materne

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Dec 7, 2021, 1:28:49 AM12/7/21
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Wouldnt it be better to combine builder with javax.validation annotations? And I havent tested if Lombok supports that already ... maybe via config file and copyableannotations ...

Jan

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ololoshka

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Dec 7, 2021, 4:35:52 AM12/7/21
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Javax annotation is trash in general. But even lombok would support it they wont be compile time safe. 

вторник, 7 декабря 2021 г. в 06:28:49 UTC, Jan:

Michael Berry

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Dec 7, 2021, 4:37:57 AM12/7/21
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This has come up quite a bit in the past, there's a good wiki page around it: https://github.com/projectlombok/lombok/wiki/FEATURE-IDEA:-%22Mandatory%22-fields-with-@Builder



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Thanks,

Michael

Michael Ernst

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Dec 7, 2021, 8:33:40 AM12/7/21
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A solution to this problem exists, in the form of a compiler plugin that is compatible with Lombok and that issues a compile-time error if a builder client might fail to set a mandatory field.

The tool is called the Called Methods Checker.  It is distributed as part of the Checker Framework and it has built-in support for Lombok builders.  It does not require you to change your coding style and it does not change the code that Lombok emits.  It does require some programmer-written annotations -- in experiments, about one per 1600 lines of non-comment, non-blank Java code.  The plugin is sound:  if it issues no errors, then your code never fails to supply all mandatory fields.  Like any static analysis tool, it can issue false positive warnings that you suppress with a @SuppressWarnings annotation.  It works best together with the io.freefair.lombok Gradle plugin.

Full disclosure:  I am not the author of the Called Methods Checker, but I did contribute to it.  Please give it a try and submit a bug report if you have any problems.

-Mike

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