Refactor com.vaadin.flow.data.binder.Binder

[mshabarov]

Describe your motivation

Binder class is a hotspot and has code health index = 5 out of 10 (Problematic), thus needs a refactoring.

Modularity Issue
Binder has a total of ~167 functions, which put it at risk of evolving into a Brain Class. Brain Classes are problematic since changes become more complex over time, harder to test, and challenging to refactor.

Complex Method
7 methods have high complexity:

• bindProperty(cc = 22)
• writeRecord(cc = 18)
• doWriteIfValid(cc = 13)
• validate(cc = 11)
• Binder.BindingBuilderImpl.bind(cc = 10)
• doWriteDraft(cc = 9)
• Binder.BindingImpl.execute(cc = 9)

A Complex Method has a high cyclomatic complexity. The recommended threshold for the Java language is a cyclomatic complexity lower than 9.

Complex Conditional

4 methods have complex conditionals.

• bindInstanceFields:3686(3 complex conditional expressions)
• Binder.BindingBuilderImpl.bind:1150(2 complex conditional expressions)
• Binder.BindingBuilderImpl.withValidator:1182(2 complex conditional expressions)
• Binder.BindingImpl.initFieldValue:1535(2 complex conditional expressions)

Inner classes and interfaces
Implementation inner classes can be extracted onto the outer new class in a backwards compatible way.

Additional context

See CodeScene analysis.