Provide a generic json mapper for any entity.

data/src/main/java/com/fernandocejas/android10/sample/data/entity/mapper/UserEntityJsonMapper.java → data/src/main/java/com/fernandocejas/android10/sample/data/entity/mapper/EntityJsonMapper.java

@@ -15,62 +15,76 @@
  */
 package com.fernandocejas.android10.sample.data.entity.mapper;
 
-import com.fernandocejas.android10.sample.data.entity.UserEntity;
 import com.google.gson.Gson;
 import com.google.gson.JsonSyntaxException;
 import com.google.gson.reflect.TypeToken;
+
+import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
 import java.util.List;
-import javax.inject.Inject;
 
 /**
  * Class used to transform from Strings representing json to valid objects.
  */
-public class UserEntityJsonMapper {
+public class EntityJsonMapper<T> {
 
   private final Gson gson;
+  private final Type type;
+  private ParameterizedType parameterizedType;
 
-  @Inject
-  public UserEntityJsonMapper() {
+  public EntityJsonMapper(Class<T> clazz) {
     this.gson = new Gson();
+    this.type = clazz;
   }
 
   /**
-   * Transform from valid json string to {@link UserEntity}.
+   * Transform from valid json string to an object type {@link T}.
    *
-   * @param userJsonResponse A json representing a user profile.
-   * @return {@link UserEntity}.
+   * @param json A json representing an object type {@link T}.
+   * @return {@link T}.
    * @throws com.google.gson.JsonSyntaxException if the json string is not a valid json structure.
    */
-  public UserEntity transformUserEntity(String userJsonResponse) throws JsonSyntaxException {
+  public T transformEntity(String json) throws JsonSyntaxException {
     try {
-      Type userEntityType = new TypeToken<UserEntity>() {}.getType();
-      UserEntity userEntity = this.gson.fromJson(userJsonResponse, userEntityType);
-
-      return userEntity;
+      return gson.fromJson(json, type);
     } catch (JsonSyntaxException jsonException) {
       throw jsonException;
     }
   }
 
   /**
-   * Transform from valid json string to List of {@link UserEntity}.
+   * Transform from valid json string to List of {@link T}.
    *
-   * @param userListJsonResponse A json representing a collection of users.
-   * @return List of {@link UserEntity}.
+   * @param json A json representing a collection of objects type {@link T}.
+   * @return List of {@link T}.
    * @throws com.google.gson.JsonSyntaxException if the json string is not a valid json structure.
    */
-  public List<UserEntity> transformUserEntityCollection(String userListJsonResponse)
+  public List<T> transformEntityCollection(String json)
       throws JsonSyntaxException {
-
-    List<UserEntity> userEntityCollection;
     try {
-      Type listOfUserEntityType = new TypeToken<List<UserEntity>>() {}.getType();
-      userEntityCollection = this.gson.fromJson(userListJsonResponse, listOfUserEntityType);
-
-      return userEntityCollection;
+      return gson.fromJson(json, getParameterizedType());
     } catch (JsonSyntaxException jsonException) {
       throw jsonException;
     }
   }
+
+  private ParameterizedType getParameterizedType() {
+    if (parameterizedType == null) {
+      parameterizedType = new ParameterizedType() {
+        @Override public Type[] getActualTypeArguments() {
+          return new Type[] {type};
+        }
+
+        @Override public Type getOwnerType() {
+          return null;
+        }
+
+        @Override public Type getRawType() {
+          return List.class;
+        }
+      };
+    }
+
+    return parameterizedType;
+  }
 }

data/src/main/java/com/fernandocejas/android10/sample/data/net/RestApiImpl.java

@@ -19,7 +19,7 @@
 import android.net.ConnectivityManager;
 import android.net.NetworkInfo;
 import com.fernandocejas.android10.sample.data.entity.UserEntity;
-import com.fernandocejas.android10.sample.data.entity.mapper.UserEntityJsonMapper;
+import com.fernandocejas.android10.sample.data.entity.mapper.EntityJsonMapper;
 import com.fernandocejas.android10.sample.data.exception.NetworkConnectionException;
 import com.fernandocejas.frodo.annotation.RxLogObservable;
 import java.net.MalformedURLException;
@@ -32,20 +32,20 @@
 public class RestApiImpl implements RestApi {
 
   private final Context context;
-  private final UserEntityJsonMapper userEntityJsonMapper;
+  private final EntityJsonMapper<UserEntity> entityJsonMapper;
 
   /**
    * Constructor of the class
    *
    * @param context {@link android.content.Context}.
-   * @param userEntityJsonMapper {@link UserEntityJsonMapper}.
+   * @param entityJsonMapper {@link EntityJsonMapper}.
    */
-  public RestApiImpl(Context context, UserEntityJsonMapper userEntityJsonMapper) {
-    if (context == null || userEntityJsonMapper == null) {
+  public RestApiImpl(Context context, EntityJsonMapper entityJsonMapper) {
+    if (context == null || entityJsonMapper == null) {
       throw new IllegalArgumentException("The constructor parameters cannot be null!!!");
     }
     this.context = context.getApplicationContext();
-    this.userEntityJsonMapper = userEntityJsonMapper;
+    this.entityJsonMapper = entityJsonMapper;
   }
 
   @RxLogObservable
@@ -55,7 +55,7 @@ public RestApiImpl(Context context, UserEntityJsonMapper userEntityJsonMapper) {
         try {
           String responseUserEntities = getUserEntitiesFromApi();
           if (responseUserEntities != null) {
-            subscriber.onNext(userEntityJsonMapper.transformUserEntityCollection(
+            subscriber.onNext(entityJsonMapper.transformEntityCollection(
                 responseUserEntities));
             subscriber.onCompleted();
           } else {
@@ -77,7 +77,7 @@ public RestApiImpl(Context context, UserEntityJsonMapper userEntityJsonMapper) {
         try {
           String responseUserDetails = getUserDetailsFromApi(userId);
           if (responseUserDetails != null) {
-            subscriber.onNext(userEntityJsonMapper.transformUserEntity(responseUserDetails));
+            subscriber.onNext(entityJsonMapper.transformEntity(responseUserDetails));
             subscriber.onCompleted();
           } else {
             subscriber.onError(new NetworkConnectionException());

data/src/main/java/com/fernandocejas/android10/sample/data/repository/datasource/UserDataStoreFactory.java

@@ -18,7 +18,8 @@
 import android.content.Context;
 import android.support.annotation.NonNull;
 import com.fernandocejas.android10.sample.data.cache.UserCache;
-import com.fernandocejas.android10.sample.data.entity.mapper.UserEntityJsonMapper;
+import com.fernandocejas.android10.sample.data.entity.UserEntity;
+import com.fernandocejas.android10.sample.data.entity.mapper.EntityJsonMapper;
 import com.fernandocejas.android10.sample.data.net.RestApi;
 import com.fernandocejas.android10.sample.data.net.RestApiImpl;
 import javax.inject.Inject;
@@ -58,8 +59,8 @@ public UserDataStore create(int userId) {
    * Create {@link UserDataStore} to retrieve data from the Cloud.
    */
   public UserDataStore createCloudDataStore() {
-    UserEntityJsonMapper userEntityJsonMapper = new UserEntityJsonMapper();
-    RestApi restApi = new RestApiImpl(this.context, userEntityJsonMapper);
+    EntityJsonMapper<UserEntity> entityJsonMapper = new EntityJsonMapper<>(UserEntity.class);
+    RestApi restApi = new RestApiImpl(this.context, entityJsonMapper);
 
     return new CloudUserDataStore(restApi, this.userCache);
   }

data/src/test/java/com/fernandocejas/android10/sample/data/entity/mapper/UserEntityJsonMapperTest.java → data/src/test/java/com/fernandocejas/android10/sample/data/entity/mapper/EntityMapperUtilTest.java

@@ -28,7 +28,7 @@
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.MatcherAssert.assertThat;
 
-public class UserEntityJsonMapperTest extends ApplicationTestCase {
+public class EntityMapperUtilTest extends ApplicationTestCase {
 
   private static final String JSON_RESPONSE_USER_DETAILS = "{\n"
       + "    \"id\": 1,\n"
@@ -49,19 +49,19 @@ public class UserEntityJsonMapperTest extends ApplicationTestCase {
       + "    \"followers\": 1381\n"
       + "}]";
 
-  private UserEntityJsonMapper userEntityJsonMapper;
+  private EntityJsonMapper<UserEntity> entityJsonMapper;
 
   @Rule
   public ExpectedException expectedException = ExpectedException.none();
 
   @Before
   public void setUp() {
-    userEntityJsonMapper = new UserEntityJsonMapper();
+    entityJsonMapper = new EntityJsonMapper<UserEntity>(UserEntity.class);
   }
 
   @Test
   public void testTransformUserEntityHappyCase() {
-    UserEntity userEntity = userEntityJsonMapper.transformUserEntity(JSON_RESPONSE_USER_DETAILS);
+    UserEntity userEntity = entityJsonMapper.transformEntity(JSON_RESPONSE_USER_DETAILS);
 
     assertThat(userEntity.getUserId(), is(1));
     assertThat(userEntity.getFullname(), is(equalTo("Simon Hill")));
@@ -71,7 +71,7 @@ public void testTransformUserEntityHappyCase() {
   @Test
   public void testTransformUserEntityCollectionHappyCase() {
     Collection<UserEntity> userEntityCollection =
-        userEntityJsonMapper.transformUserEntityCollection(
+        entityJsonMapper.transformEntityCollection(
             JSON_RESPONSE_USER_COLLECTION);
 
     assertThat(((UserEntity) userEntityCollection.toArray()[0]).getUserId(), is(1));
@@ -82,12 +82,12 @@ public void testTransformUserEntityCollectionHappyCase() {
   @Test
   public void testTransformUserEntityNotValidResponse() {
     expectedException.expect(JsonSyntaxException.class);
-    userEntityJsonMapper.transformUserEntity("ironman");
+    entityJsonMapper.transformEntity("ironman");
   }
 
   @Test
   public void testTransformUserEntityCollectionNotValidResponse() {
     expectedException.expect(JsonSyntaxException.class);
-    userEntityJsonMapper.transformUserEntityCollection("Tony Stark");
+    entityJsonMapper.transformEntityCollection("Tony Stark");
   }
 }