Retrofit動態(tài)更換baseUrl

1.一般一個(gè)應(yīng)用都只創(chuàng)建一個(gè)Retrofit實(shí)例唬党，但是當(dāng)碰到需要的網(wǎng)絡(luò)請求的baseUrl不止一個(gè)的時(shí)候驶拱，就要考慮如何給retrofit對象根據(jù)不同的請求接口更換不同的baseUrl了。

2.實(shí)現(xiàn)方法如下

    companion object{

        private const val DEFAULT_TIME:Long=30*1000

        private var okHttpClient=OkHttpClient.Builder().connectTimeout(DEFAULT_TIME,TimeUnit.MILLISECONDS)
            .writeTimeout(DEFAULT_TIME,TimeUnit.MILLISECONDS).readTimeout(DEFAULT_TIME,TimeUnit.MILLISECONDS).addInterceptor(
                HttpLoggingInterceptor().setLevel(HttpLoggingInterceptor.Level.BASIC)
            ).addInterceptor(ChangeBaseUrlInterceptor())
            .retryOnConnectionFailure(true).build()


        private var retrofit: Retrofit = Retrofit.Builder().client(okHttpClient)
            .baseUrl(Constants.BaseUrl) //設(shè)置網(wǎng)絡(luò)請求的Url地址
            .addConverterFactory(GsonConverterFactory.create()) //設(shè)置數(shù)據(jù)解析器
            .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
            .build()


        @JvmStatic
        fun isNetworkAvailable(): Boolean {
            val connectivity = AbsApplication.getInstance().getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
            if (connectivity == null) {
                return false
            } else {
                val info = connectivity.allNetworkInfo
                if (info != null) {
                    for (i in info.indices) {
                        if (info[i].state == NetworkInfo.State.CONNECTED) {
                            return true
                        }
                    }
                }
            }
            return false
        }

        @JvmStatic
        fun isNetworkOnWifi(): Boolean {
            val connectivity =
                AbsApplication.getInstance().getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
            if (connectivity != null) {
                val info = connectivity.allNetworkInfo
                if (info != null) {
                    for (i in info.indices) {
                        if (info[i].typeName == "WIFI" && info[i].isConnected) {
                            return true
                        }
                    }
                }
            }
            return false
        }


        fun <T> getApiService(reqService: Class<T>): T {
            return retrofit!!.create(reqService)
        }
    }

3.API Server 接口定義如下

interface ApiService {

    @Headers("domin:login")
    @GET("values/5")
    fun getRetrofit(): Call<BaseResponse<DemoBean>>

    @Headers("domin:loginother")
    @GET("values/5")
    fun getRetrofitObserver(): Observable<BaseResponse<DemoBean>>

    @POST
    @Headers("Content-Type:application/json;charset=utf-8")
    fun getAnswerObserver(@Url url:String,@Body body: RequestBody): Observable<Answer>


    @POST
    @Headers("Content-Type:application/json;charset=utf-8")
    fun messagePush(@Url url: String,@Body body:RequestBody):Observable<PushResult>

    @GET("/session")
    fun getSession():Observable<ResponseBody>

}

這幾個(gè)接口的baseUrl都是不一樣的晌纫，怎么區(qū)分呢，通過給接口添加注解锹漱，設(shè)置其請求頭屬性domin的值
下面看一下自定義攔截器是怎么根據(jù)請求頭的domin屬性更換為每個(gè)接口更換baseUrl的


object  URLConstant{
   const val BASE_URL = "https://login.weixin.qq.com"
    const val BASE_LOGIN_URL = "https://wx.qq.com"
    const val BASE_LOGIN_OTHER_URL = "https://wx2.qq.com"
    const val LOGIN_OTHER = "loginother"
    const val LOGIN = "login"
    const val DOMAIN = "domain"
}
class ChangeBaseUrlInterceptor :Interceptor{

    override fun intercept(chain: Interceptor.Chain): Response {
        //獲取request
        var request=chain.request()

        //從request中獲取原有的HttpUrl實(shí)列 oldHttpUrl

        var oldHttpUrl=request.url()

        //獲取request的創(chuàng)建者
        var builder=request.newBuilder()

        //從request中獲取headers 通過給定的建的url_name

        var headerValues=request.headers(URLConstant.DOMAIN)

        if(headerValues!=null&&headerValues.size>0) {
            builder.removeHeader(URLConstant.DOMAIN)

            var headValue = headerValues[0]

            var newBaseUrl: HttpUrl?

            newBaseUrl = when (headValue) {
                URLConstant.LOGIN -> {
                    HttpUrl.parse(URLConstant.BASE_LOGIN_URL)
                }
                URLConstant.LOGIN_OTHER -> {
                    HttpUrl.parse(URLConstant.BASE_LOGIN_OTHER_URL)
                }
                else -> {
                    HttpUrl.parse(URLConstant.BASE_URL)
                }
            }
       newBaseUrl?.run {
                var newHttpUrl =
                    oldHttpUrl.newBuilder().scheme(scheme()).host(host())
                        .port(port()).build()
                return chain.proceed(builder.url(newHttpUrl).build())
            }
        }
        return chain.proceed(request)
    }

}

這是一個(gè)自定義的網(wǎng)絡(luò)請求攔截器毕泌，在創(chuàng)建Retrofit對象的時(shí)候已經(jīng)把攔截器設(shè)置給了Retrofit,那么網(wǎng)絡(luò)請求就會分發(fā)到這個(gè)攔截器，這個(gè)攔截器接收到網(wǎng)絡(luò)請求之后撼泛，就會根據(jù)需求對網(wǎng)絡(luò)請求做一些處理，然后再通過請求鏈把這個(gè)網(wǎng)絡(luò)請求再向下一個(gè)攔截器分發(fā)愿题。這個(gè)過程使用了責(zé)任鏈的設(shè)計(jì)模式，就是當(dāng)一個(gè)任務(wù)下達(dá)之后潘酗，從上一級交由下一級處理，上一級可以根據(jù)實(shí)際情況是攔截任務(wù)自己處理還是繼續(xù)分發(fā)給下一級琐脏，這個(gè)任務(wù)最終會被某一級處理掉或者都無法處理被拋棄掉囚灼，這個(gè)就和Android的view事件分發(fā)機(jī)制的原理是一樣的祭衩。

Http請求采用這種責(zé)任鏈模式的好處是網(wǎng)絡(luò)請求可以分層處理，每一層只實(shí)現(xiàn)某一特定功能即可掐暮，這樣對整個(gè)過程進(jìn)行了解耦，易于理解路克。Retrofit請求更換baseUrl就是這樣實(shí)現(xiàn)的