Quick fix action to refactor field injection to constructor injection

In general, field injection comes with some downsides http://olivergierke.de/2013/11/why-field-injection-is-evil/

Unfortunately, refactoring of old, grown code bases towards constructor injection is tedious. So I was looking for a refactoring automation (and apparently I was not the first one with this issue https://stackoverflow.com/questions/44008985/convert-spring-field-injection-to-constructor-injection-intellij-idea)

So in essence, a quick fix action on @Inject or @Autowired fields to create a new or extend an existing constructor (depending on (required = false) flag) would be really nice.

[BoykoAlex]

@MahatmaFatalError A parameter is to be added to a constructor if the constructor meets the following criteria:

1. No constructors. Constructor is created and is not annotated.
2. Only one constructor. Parameter is added.
3. Multiple constructors, only one annotated with @Autowired. This constructor is added a parameter.

Therefore, this refactoring doesn’t add @Autowired. @martinlippert was referring to the use case in your screenshots. First screenshot - no constructor case. The new constructor doesn’t get the annotation and it is a good practice.

[martinlippert]

@MahatmaFatalError This belongs to a broader effort that we are working on at the moment to integrate refactorings and code changes using https://github.com/openrewrite, so the code change part of this quick fix is actually implemented in https://github.com/openrewrite/rewrite-spring.

Since this is an early stage and not yet meant for mainstream consumption, you need to enable this in the preferences via Preferences -> Language Servers -> Spring Language Servers -> Spring Boot Language Server and then check Experimental reconciling for Java sources based on Rewrite project. Once you have that setting enabled, the quick fix will appear on code like this:

	@Autowired
	private MyService service;

When you put the cursor on @Autowired or service and hit the shortcut for Quick Fix, you will see a quick fix appearing called Convert @Autowired field into Constructor Parameter.

But keep in mind, this is a very early, experimental feature and not yet optimized or meant for mainstream consumption. It is early work towards enabling a broader set of new Spring-related refactorings, validations, and automated code changes.

Hope this helps. Feedback always welcome!!!