Handle http request path changes in runtime with retrofit

Question

I have this api usage now:

App.API.foo(mapOf("a" to a, "b" to b)).enqueue(responseHandler)

// my api class
@POST("/foo-v1")
fun foo(@Body map: Map<String, String>): Call<Response>

Now I have new api path: "/foo-v2" and new baseurl that defined in runtime.

What can be my best way to do changes in runtime? option that I think: to add @Path("version") version: String to foo function will be like this:

@POST("/foo-{version}") 
fun foo(@Body map: Map<String, String>, @Path("version") version: String): Call<Response>

its ok for one single request but in case when changed a lot of requests its not so good.

Ps another question, what can be done when for some requests need also add new path like @POST("/auth/foo-{version}")

Answer 1

I originally commented because I'm short on time, but I wanted to offer some quick code to illustrate the point.

Given a service like this:

interface ChangePathService {
    @POST(".")
    fun foo(
        @Header("path") path: String,
        @Body map: Map<String, String>
    ): Call<Response>
}

You can set your endpoint path at run time using an interceptor, which is applied to your OkHttpClient.Builder.

class ChangePathInterceptor(
    private val baseUrl: String,
): Interceptor {
    override fun intercept(chain: Interceptor.Chain): Response {
        // This request is has "." as the path. We want to change it!
        val request = chain.request()

        /**
         * Get the path argument via the headers. I exit early here 
         * with the original request going through the network but you
         * can throw an exception or whatever.
         */
        val path = request.header("path")
            ?: return chain.proceed(request)

        val body = request.body // don't forget to apply your request body

        /**
         * Here's where you create your new request at runtime!
         */

        val newRequest = Request.Builder()
            .url(baseUrl+path)
            .headers(request.headers)
            .apply {
                if(body == null) this else post(body)
            }
            .build()

        return chain.proceed(newRequest)
    }
} 

EDIT: The path can be managed at runtime from the service endpoint call site. For example, a repository:

class SomeRepository(
    private val service: ChangePathService,
) {
    
    private fun getFooVersion(): String {
        // do your version logic here.
    }

    fun callFoo(map: Map<String, String>) {

        val version: String = getFooVersion() // this could be calculated once at the repository level depending on your need

        val call = service.foo(
            path = "/foo-$version", // interpolate version here
            body = map,
        )
        
        call.enqueue(responseHandler)
    }

    ...
}