Examples for retrofit guide (#2596)

libraries/pom.xml

@@ -517,6 +517,11 @@
             <groupId>com.squareup.retrofit2</groupId>
             <artifactId>adapter-rxjava</artifactId>
             <version>${retrofit.version}</version>
+        </dependency>        
+        <dependency>
+            <groupId>com.squareup.okhttp3</groupId>
+            <artifactId>logging-interceptor</artifactId>
+            <version>3.9.0</version>
         </dependency>
         <dependency>
             <groupId>com.darwinsys</groupId>

libraries/src/main/java/com/baeldung/retrofitguide/GitHubServiceGenerator.java

@@ -0,0 +1,58 @@
+package com.baeldung.retrofitguide;
+
+import java.io.IOException;
+import okhttp3.Interceptor;
+import okhttp3.OkHttpClient;
+import okhttp3.Request;
+import okhttp3.Response;
+import okhttp3.logging.HttpLoggingInterceptor;
+import retrofit2.Retrofit;
+import retrofit2.converter.gson.GsonConverterFactory;
+
+public class GitHubServiceGenerator {
+
+    private static final String BASE_URL = "https://api.github.com/";
+
+    private static Retrofit.Builder builder
+            = new Retrofit.Builder()
+                    .baseUrl(BASE_URL)
+                    .addConverterFactory(GsonConverterFactory.create());
+
+    private static Retrofit retrofit = builder.build();
+
+    private static OkHttpClient.Builder httpClient
+            = new OkHttpClient.Builder();
+
+    private static HttpLoggingInterceptor logging
+            = new HttpLoggingInterceptor()
+                    .setLevel(HttpLoggingInterceptor.Level.BASIC);
+
+    public static <S> S createService(Class<S> serviceClass) {
+        if (!httpClient.interceptors().contains(logging)) {
+            httpClient.addInterceptor(logging);
+            builder.client(httpClient.build());
+            retrofit = builder.build();
+        }
+        return retrofit.create(serviceClass);
+    }
+
+    public static <S> S createService(Class<S> serviceClass, final String token) {
+        if (token != null) {
+            httpClient.interceptors().clear();
+            httpClient.addInterceptor(new Interceptor() {
+                @Override
+                public Response intercept(Interceptor.Chain chain) throws IOException {
+                    Request original = chain.request();
+                    Request.Builder builder = original.newBuilder()
+                            .header("Authorization", token);
+                    Request request = builder.build();
+                    return chain.proceed(request);
+                }
+            });
+            builder.client(httpClient.build());
+            retrofit = builder.build();
+        }
+        return retrofit.create(serviceClass);
+    }
+
+}

libraries/src/main/java/com/baeldung/retrofitguide/Main.java

@@ -0,0 +1,49 @@
+package com.baeldung.retrofitguide;
+
+import java.io.IOException;
+import okhttp3.OkHttpClient;
+import retrofit2.Call;
+import retrofit2.Callback;
+import retrofit2.Response;
+import retrofit2.Retrofit;
+import retrofit2.converter.gson.GsonConverterFactory;
+
+public class Main {
+
+    public static void main(String[] args) {
+        //Manual creation
+        OkHttpClient.Builder httpClient = new OkHttpClient.Builder();
+        Retrofit retrofit = new Retrofit.Builder()
+                .baseUrl("https://api.github.com/")
+                .addConverterFactory(GsonConverterFactory.create())
+                .client(httpClient.build())
+                .build();
+        UserService service = retrofit.create(UserService.class);
+        //Using GitHubServiceGenerator
+        service = GitHubServiceGenerator.createService(UserService.class);
+        Call<User> callSync = service.getUser("eugenp");
+        Call<User> callAsync = service.getUser("eugenp");
+
+        try {
+            Response<User> response = callSync.execute();
+            User user = response.body();
+            System.out.println(user);
+        } catch (IOException ex) {
+        }
+
+        // Execute the call asynchronously. Get a positive or negative callback.
+        callAsync.enqueue(new Callback<User>() {
+            @Override
+            public void onResponse(Call<User> call, Response<User> response) {
+                User user = response.body();
+                System.out.println(user);
+            }
+
+            @Override
+            public void onFailure(Call<User> call, Throwable throwable) {
+                System.out.println(throwable);
+            }
+        });
+
+    }
+}

libraries/src/main/java/com/baeldung/retrofitguide/User.java

@@ -0,0 +1,65 @@
+package com.baeldung.retrofitguide;
+
+public class User {
+
+    private String login;
+    private long id;
+    private String url;
+    private String company;
+    private String blog;
+    private String email;
+
+    public String getLogin() {
+        return login;
+    }
+
+    public void setLogin(String login) {
+        this.login = login;
+    }
+
+    public long getId() {
+        return id;
+    }
+
+    public void setId(long id) {
+        this.id = id;
+    }
+
+    public String getUrl() {
+        return url;
+    }
+
+    public void setUrl(String url) {
+        this.url = url;
+    }
+
+    public String getCompany() {
+        return company;
+    }
+
+    public void setCompany(String company) {
+        this.company = company;
+    }
+
+    public String getBlog() {
+        return blog;
+    }
+
+    public void setBlog(String blog) {
+        this.blog = blog;
+    }
+
+    public String getEmail() {
+        return email;
+    }
+
+    public void setEmail(String email) {
+        this.email = email;
+    }
+
+    @Override
+    public String toString() {
+        return "User{" + "login=" + login + ", id=" + id + ", url=" + url + ", company=" + company + ", blog=" + blog + ", email=" + email + '}';
+    }
+
+}

libraries/src/main/java/com/baeldung/retrofitguide/UserService.java

@@ -0,0 +1,17 @@
+package com.baeldung.retrofitguide;
+
+import java.util.List;
+import retrofit2.Call;
+import retrofit2.http.GET;
+import retrofit2.http.Path;
+import retrofit2.http.Query;
+
+public interface UserService {
+
+    @GET("/users")
+    public Call<List<User>> getUsers(@Query("per_page") int per_page, @Query("page") int page);
+
+    @GET("/users/{username}")
+    public Call<User> getUser(@Path("username") String username);
+
+}