Simplify MediaType.parse Calls

[AlekSimpson]

What's changed?

This PR introduces a recipe to replaces uses of MediaType.parse("application/json") with MediaType.APPLICATION_JSON.

What's your motivation?

Fixes #337

Anything in particular you'd like reviewers to focus on?

Currently when the recipe runs the methodType for MediaType.parse is null which is causing the recipe to stop running early. I think it is because I am not including the correct classpath. I have tried using classpath("spring-web") but it kept telling me that this was not a valid resource name. I'm confused why it would tell me that since I've seen spring-web used in other tests in rewrite-spring.

Anyone you would like to review specifically?

@timtebeek

Checklist

• I've added unit tests to cover both positive and negative cases
• I've added the license header to any new files through ./gradlew licenseFormat
• I've used the IntelliJ auto-formatter on affected files
• I've updated the documentation (if applicable)

[joanvr]

The reason why it's returning null is because the method parse(String) does not actually exist in MediaType. I understand that you are using this method name because of the original issue, but if you check at the docs it seems that the method you are looking for is called parseMediaType(String) or maybe valueOf(String), probably both... if you take a look at the code it calls the first one.
Maybe it's a typo? Or the API just changed at some point? I could not find any reference to MediaType.parse(String) from Spring in a fast google search.

P.D.: Also added spring-core in the classpath of the test, since it's needed as a dependency of spring-web for properly parsing org.springframework.http.MediaType

[timtebeek]

This is perhaps too limiting; we already have a recipe to replace literals with constants:

• Replace String literals with constants for HttpHeaders and MediaTypes #325

A comment there was logged as an improvement to pick up cases where we (after the above recipe) pass a constant into a parse method:

• Simplify unnecessary MediaType.parse calls #337

If you ask me this implementation should detect String constants passed into parse, and replace those with the pre existing MediaType constants. Open to discuss.

[AlekSimpson]

Ok so just to make sure I understand this correctly instead of detecting something like "application/json" like we are doing now; We should instead detect constants and make the replacement then?

Are there are other MediaType constants this recipe should try covering also? Instead of just looking for APPLICATION_JSON?

[timtebeek]

yes when the value feeding into the parse call is a constant defined on MediaType then you want to replace the whole method invocation with the sister constant.

[timtebeek]

so

-MediaType.parseMediaType(MediaType.APPLICATION_JSON_VALUE)
+MediaType.APPLICATION_JSON

notice how we drop the method call, and replace it with a "sister constant" that lacks the _VALUE suffix.

[timtebeek]

the above is from memory, so be sure to check what's available on the MediaType class in your IDE, but that's the rough outline of what I would expect. And we should not limit ourselves to APPLICATION_JSON, instead just any constants that follow that pattern (without naming each explicitly).

[AlekSimpson]

Ok I updated this recipe to work not just with APPLICATION_JSON_VALUE but also with the other constants that MediaType has. It also was modified to only with constants and not literals.

[timtebeek]

Make a small change not to use a hardcoded list of variables, instead using the convention that if there's a String constant defined on MediaType that there's a matching constant that lacks the _VALUE suffix. We also don't need to use JavaTemplate for such a replacement.