Retrofit post a object parameter, but receive a "parameter is not present" error

Question

Here is my spring boot controller:

@RestController
@RequestMapping("/api/v1/geo-media/")
class GeoMediaController {
@PostMapping("create")
    fun saveMedias(@RequestHeader("token") token: String,
                   @RequestParam mediaGroup: WalkMediaGroup):Result<String> {
    }
}

Here is the parameter class:

class WalkMediaGroup (
    val wid: Long,
    val mediaGroup: MediaGroup
)

class MediaGroup(
    val node: Node,
    val medias: List<Media>
)

class Media (
    val type: Int,
    val content: String,
    val remark: String
)

Then my Retrofit service class:

interface ApiService {
    @Headers("Content-Type: application/json")
    @POST("geo-media/create")
    fun createGeoMedias(
        @Body mediaGroup: WalkMediaGroup
    ): Call<Result<String>>
}

Above is the key parts of my code. I don't know why that I received error.

{
    "timestamp":"2019-10-25T11:46:10.247+0000",
    "status":400,
    "error":"Bad Request",
    "message":"Required WalkMediaGroup parameter 'mediaGroup' is not present",
 ......
}

Answer 1

From Android (or whatever the client it maybe) you're posting JSON body. In order to receive that JSON body parameter in server you've to use Spring Boot @RequestBody() annotation instead of @RequestParam() annotation.

So, in your Spring Boot API code just change the annotation from @RequestParam() to @RequestBody(). That's it!

@PostMapping("create")
fun saveMedias(
    @RequestHeader("token") token: String,
   /* notice the change here ==> */ @RequestBody mediaGroup: WalkMediaGroup):Result<String> {
}