The technical principles of the Retrofit framework in the Java library (Detailed Explanation of Technical Principles of Retrofit Framework in Java Class Libraries)

Retrofit is a framework for building an HTTP request client in the Java library.It is developed by Square to simplify network requests. Retrofit uses annotations to define the network request interface and request parameters, and then generate the corresponding execution code based on these annotations.Let's explain in detail the technical principles of the Retrofit framework in the Java library. 1. Define the network request interface: First, use the Java interface to define the interface of the network request.Define the requested URL, request method (get, post, etc.), request parameters, request header, etc. by adding annotations to the interface method. public interface ApiService { @GET("users/{id}") Call<User> getUser(@Path("id") int userId); @POST("users") Call<User> createUser(@Body User user); // ... } 2. Create a Retrofit instance: Next, we need to create a Retrofit instance to process the configuration of the network request.You can create a RETROFIT instance through the Builder mode, and specify the basic URL, converter (used to convert the request results into Java objects), interceptor (for adding the request header, printing request log, etc.). Retrofit retrofit = new Retrofit.Builder() .baseUrl("http://api.example.com/") .addConverterFactory(GsonConverterFactory.create()) .build(); 3. Create a network request interface instance: Use a retrofit instance to create an instance of the network request interface.RETROFIT will generate code to perform network requests according to the interface definition and annotation. ApiService apiService = retrofit.create(ApiService.class); 4. Initiating network requests: The network request is initiated by calling the method of calling the network request interface instance.Retrofit generates the corresponding request URL and request body according to the annotation and parameters, and sends the request to the server. Call<User> call = apiService.getUser(123); call.enqueue(new Callback<User>() { @Override public void onResponse(Call<User> call, Response<User> response) { if (response.isSuccessful()) { User user = response.body(); // Treatment back results } else { // The processing request failed } } @Override public void onFailure(Call<User> call, Throwable t) { // Treatment requests abnormally } }); 5. Processing the results of the network request: process the network request results by the way the callback function.When the request is successful, the Retrofit will analyze the result return of the server as the Java object and return it through the callback function.When the request fails or abnormalities, the failure method of callback function will be called. To sum up, the technical principles of the RETROFIT framework mainly involve annotation analysis, dynamic proxy, and the sending and response processing of HTTP requests.Through annotations, Retrofit can generate code that executes network requests, simplifying the development of developers.At the same time, it also provides a wealth of expansion mechanisms that can customize converters, interceptors, etc. to further meet the needs in different scenarios. I hope that this article can help you understand the technical principles of the Retrofit framework in the Java class library, and provide guidance and help for your future development of the network request related functions.