Android retrofit - date format when passing datetime by URL

Question

I have API method mapping like this

@POST("api/updateStarted/{id}/{started}")
suspend fun updateStarted(
    @Path("id") id: Int,
    @Path("started") started: Date
) : Response <Int>

I want to use yyyy-MM-dd'T'HH:mm:ss format everywhere. My API adapter looks like this:

val gson = GsonBuilder().setDateFormat("yyyy-MM-dd'T'HH:mm:ss")

val apiClient: ApiClient = Retrofit.Builder()
    .addConverterFactory(GsonConverterFactory.create(gson.create()))
    .baseUrl(API_BASE_URL)
    .client(getHttpClient(API_USERNAME, API_PASSWORD))
    .addConverterFactory(GsonConverterFactory.create())
    .build()
    .create(ApiClient::class.java)

However GsonBuilder().setDateFormat("yyyy-MM-dd'T'HH:mm:ss") cannot affect date format when I pass it thru URL (because that's not JSON) so Retrofit builds URL like this:

http://myserver.com/api/updateFinished/2/Fri%20Jan%2027%2013:48:42%20GMT+01:00%202023 

instead of something like this:

http://myserver.com/api/updateFinished/2/2023-01-28T02:03:04.000

How can I fix that? I'm new in Retrofit and I don't fully understand date/time libraries in Java.

Answer 1

You can switch the data type from java.util.Date to java.time.LocalDateTime if you want your desired format using the toString() method of that data type.

Currently, you have Date.toString() producing an undesired result.

If you don't have to use a Date, import java.time.LocalDateTime and just change your fun a little to this:

@POST("api/updateStarted/{id}/{started}")
suspend fun updateStarted(
    @Path("id") id: Int,
    @Path("started") started: LocalDateTime
) : Response <Int>