Retrofit的使用（二）

这部分主要是实现Retrofit的转换器使用，以及实现cookies缓存+嵌套请求，文件的上传和下载

• 相关依赖

    implementation'com.squareup.retrofit2:retrofit:2.9.0'
    implementation'com.squareup.retrofit2:converter-gson:2.9.0'
    implementation'com.google.code.gson:gson:2.8.6'
    implementation "com.squareup.retrofit2:adapter-rxjava3:2.9.0"

1、使用转换器

和前面一样，也是要创建请求的接口：

public interface WanAndroidService {
   //不使用转换器，直接使用Gson来转换
    @POST("user/login")
    @FormUrlEncoded
    Call<ResponseBody> loginWanAndroid(@Field("username") String username,@Field("password") String password);

    //使用转换器,ResponseBody只能得到字符串，用转换器转换成Bean对象
    @POST("user/login")
    @FormUrlEncoded
    Call<WanAndroidBean> loginWanAndroid2(@Field("username") String username,@Field("password") String password);
}

接着在Java环境中创建对应的测试单元（对应的WanAndroidBean .java可以用PostMan配合GsonFormat插件自动生成）：

//retrofit转换器测试
public class WandroidUnitTest {
    Retrofit retrofit = new Retrofit.Builder()
            .baseUrl("https://www.wanandroid.com/")
            .build();

    WanAndroidService wanAndroidService = retrofit.create(WanAndroidService.class);
    @Test
    public void loginTest(){
        Call<ResponseBody> call = wanAndroidService.loginWanAndroid("用户名", "密码");
        try {
            Response<ResponseBody> response = call.execute();
            String result = response.body().string();

            //第一种；使用Gson手动转换
            //将Json字符串转换成对应的对象
            WanAndroidBean wanAndroidBean = new Gson().fromJson(result,WanAndroidBean.class);
            System.out.println(wanAndroidBean.toString());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

 @Test
    public void addConvertLoginTest(){
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("https://www.wanandroid.com/")
                //第二种：添加转换器，让Retrofit自动转换，使用GsonConvertFactory将json数据转换成对象
                .addConverterFactory(GsonConverterFactory.create())
                .build();

        WanAndroidService wanAndroidService = retrofit.create(WanAndroidService.class);
        Call<WanAndroidBean> wanAndroidBeanCall = wanAndroidService.loginWanAndroid2("用户名", "密码");
        try {
            Response<WanAndroidBean> beanResponse = wanAndroidBeanCall.execute();
            WanAndroidBean wanAndroidBean = beanResponse.body();
            System.out.println(wanAndroidBean);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

2、使用嵌套请求+cookies缓存

嵌套请求是指在请求有顺序的情况下，例如必须要先登录再获取文章列表，有先后顺序，

• 封装请求的接口

public interface WanAndroidService {
   //使用适配器，与Rxjava联合使用
    @POST("user/login")
    @FormUrlEncoded
    Flowable<WanAndroidBean> login2(@Field("username")String username,@Field("password")String password);
  
    //请求文章列表
    @GET("lg/collect/list/{pageNum}/json")
    Flowable<ResponseBody> getArticle(@Path("pageNum")int pageNum);
}

• 实际请求，这里加入了Rxjava的转换器

  //使用适配器，实现嵌套请求
    Map<String,List<Cookie>> cookies = new HashMap<>();
    @Test
    public void useAdapter(){
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("https://www.wanandroid.com/")
                //配置Cookie缓存
                .callFactory(new OkHttpClient.Builder().cookieJar(new CookieJar() {
                    @Override
                    public void saveFromResponse(HttpUrl url, List<Cookie> list) {
                        cookies.put(url.host(),list);
                    }
                    @Override
                    public List<Cookie> loadForRequest(HttpUrl url) {
                        List<Cookie> cookies = WandroidUnitTest.this.cookies.get(url.host());
                        return cookies == null ? new ArrayList<>():cookies;
                    }
                }).build())
                //第二种：添加转换器，让Retrofit自动转换，使用GsonConvertFactory将json数据转换成对象
                .addConverterFactory(GsonConverterFactory.create())
                //添加适配器,让它不再是单一的Call对象，改为Rxjava的Flowable对象
                .addCallAdapterFactory(RxJava3CallAdapterFactory.create())
                .build();
        WanAndroidService wanAndroidService = retrofit.create(WanAndroidService.class);

        //使用的是Rxjava的线程切换调用
       //1.先登录
        wanAndroidService.login2("用户名", "密码")
                //生成一个新的publish
                .flatMap(new Function<WanAndroidBean, Publisher<ResponseBody>>() {
                    @Override
                    public Publisher<ResponseBody> apply(WanAndroidBean wanAndroidBean) throws Throwable {
                        //2.嵌套请求，请求文章列表
                        return wanAndroidService.getArticle(0);
                    }
                })
                .observeOn(Schedulers.io())
                .subscribeOn(Schedulers.newThread())
                .subscribe(new Consumer<ResponseBody>() {
                    @Override
                    public void accept(ResponseBody responseBody) throws Throwable {
                        System.out.println(responseBody.string());
                    }
                });

3、文件的上传和下载

• 常用文件上传格式对照

json : application/json
xml : application/xml
png : image/png
jpg : image/jpeg
gif : imge/gif
txt:text/plain
二进制数据:multipart/form-data

• 文件上传
  创建对应的请求接口

public interface UploadService {
    //文件上传1个
    @POST("post")
    @Multipart
    Call<ResponseBody> upload(@Part MultipartBody.Part file);

    //文件上传2个
    @POST("post")
    @Multipart
    Call<ResponseBody> upload2(@Part MultipartBody.Part file,@Part MultipartBody.Part file2);

    //上传多个文件
    @POST("post")
    @Multipart
    Call<ResponseBody> upload3(@PartMap Map<String, RequestBody> params);
}

对应的请求代码：

public class UploadFileUnit {

    //上传单个文件
    @Test
    public void upload(){
        Retrofit retrofit = new Retrofit.Builder().baseUrl("https://www.httpbin.org").build();
        UploadService uploadService = retrofit.create(UploadService.class);

        File file = new File("C:\\Users\\Administrator\\Desktop\\1.txt");
        MultipartBody.Part part = MultipartBody.Part
                .createFormData("file","1.txt,",RequestBody.create(MediaType.parse("text/plain"),file));
        Call<ResponseBody> call = uploadService.upload(part);
        try {
            Response<ResponseBody> response = call.execute();
            System.out.println(response.body().string());

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //上传两个文件
    @Test
    public void upload2(){
        Retrofit retrofit = new Retrofit.Builder().baseUrl("https://www.httpbin.org").build();
        UploadService uploadService = retrofit.create(UploadService.class);
        //文件1，可以将text/plain替换城multipart/form-data
        File file1 = new File("C:\\Users\\Administrator\\Desktop\\1.txt");
        MultipartBody.Part part1 = MultipartBody.Part
                .createFormData("file1","1.txt,",RequestBody.create(MediaType.parse("text/plain"),file1));
        //文件2
        File file2 = new File("C:\\Users\\Administrator\\Desktop\\2.txt");
        MultipartBody.Part part2 = MultipartBody.Part
                .createFormData("file2","2.txt,",RequestBody.create(MediaType.parse("text/plain"),file2));

        Call<ResponseBody> call = uploadService.upload2(part1,part2);
        try {
            Response<ResponseBody> response = call.execute();
            System.out.println(response.body().string());

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //上传多个文件
    @Test
    public void uploadMore(){
        Retrofit retrofit = new Retrofit.Builder().baseUrl("https://www.httpbin.org").build();
        UploadService uploadService = retrofit.create(UploadService.class);

        //发送大量二进制数据，不限于文件
        MediaType mediaType = MediaType.parse("multipart/form-data");
        Map<String,RequestBody> params = new HashMap<>();
        params.put("file[0]",MultipartBody.create(mediaType,new File("C:\\Users\\Administrator\\Desktop\\1.txt")));
        params.put("file[1]",MultipartBody.create(mediaType,new File("C:\\Users\\Administrator\\Desktop\\2.txt")));


        Call<ResponseBody> call = uploadService.upload3(params);
        try {
            Response<ResponseBody> response = call.execute();
            System.out.println(response.body().string());

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

• 文件下载

public interface DownLoadSercvice {
    //下载文件
    @Streaming
    @GET
    Call<ResponseBody> download(@Url String url);
}

对应请求：

 @Test
    public void downloadFile(){
        Call<ResponseBody> call = downLoadSercvice.download("https://pacakge.cache.wpscdn.cn/wps/download/W.P.S.10577.12012.2019.exe");
        try {
            Response<ResponseBody> response = call.execute();
            if (response.isSuccessful()){
                //以文件流的形式
                InputStream inputStream = response.body().byteStream();
                FileOutputStream fileOutputStream = new FileOutputStream("C:\\Users\\Administrator\\Desktop\\wps.exe");
                int len;
                byte[] buffer = new byte[4096];
                while ((len =inputStream.read(buffer)) != -1){
                    fileOutputStream.write(buffer,0,len);
                }
                fileOutputStream.close();
                inputStream.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }