Trailing slash added for request mappings with empty path

[Patouche]

Hello !

This may be related to this issues spring-projects/spring-framework#28552 or spring-projects/spring-framework#29625 but there is a strange behavior using spring hateoas with the removal of the trailing slash.

For example:

package com.sample

import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication
import org.springframework.hateoas.CollectionModel
import org.springframework.hateoas.RepresentationModel
import org.springframework.hateoas.server.mvc.add
import org.springframework.http.ResponseEntity
import org.springframework.web.bind.annotation.GetMapping
import org.springframework.web.bind.annotation.PathVariable
import org.springframework.web.bind.annotation.RequestMapping
import org.springframework.web.bind.annotation.RestController

data class User(val id: Int) : RepresentationModel<User>()

@SpringBootApplication
@RestController
@RequestMapping("/users")
class SampleApp {
    @GetMapping("")
    fun list() = CollectionModel.of((1..10).map { User(it) })

    @GetMapping("/{id}")
    fun single(@PathVariable id: Int) = ResponseEntity.ok(User(id).add(SampleApp::class) { linkTo { list() } withRel "up" })

}

fun main(args: Array<String>) {
    runApplication<SampleApp>(*args)
}

The endpoint http://localhost:8080/users/1 will produce the following output:

{
  "id":1,
  "_links":{
    "up": {
      "href":"http://localhost:8080/users/"
    }
  }
}

As you can notice the up link isn't correct as it will lead to 404 error page with the removal of the trailing slash. If we transform the @GetMapping("") into a @GetMapping, the link will become correct.

For the time being, I don't have time to find the root cause of this issue but I can try to take a look of what's happens here.

Regards,
Patrick