Data Modules

The data layer implements the domain layer’s gateways and handles all data operations. It’s organized into specialized modules for different data sources and concerns.

Module Overview

Local

Room database and local storage

Remote

Retrofit API and network calls

Repository

Gateway implementations

Session

DataStore preferences and session

Source

Data source interfaces

Local Module

Module: data:local Package: es.mobiledev.data.local Handles local data persistence using Room database.

AppRoomDatabase

Main Room database class for the application.

@Database(
    entities = [ArticleDbo::class],
    version = 1,
    exportSchema = false
)
abstract class AppRoomDatabase : RoomDatabase() {
    abstract fun articleDao(): ArticleDao
}

entities

Array<KClass<*>>

Database entities: ArticleDbo

version

Int

Database version: 1

ArticleDao

File: data/local/src/main/java/es/mobiledev/data/local/article/dao/ArticleDao.kt:11 Data Access Object for article operations.

@Dao
interface ArticleDao {
    @Insert(onConflict = OnConflictStrategy.REPLACE)
    suspend fun saveFavoriteArticle(article: ArticleDbo)

    @Delete
    suspend fun removeFavoriteArticle(article: ArticleDbo)

    @Query("SELECT * FROM articles")
    suspend fun getFavoriteArticles(): List<ArticleDbo>

    @Query("SELECT * FROM articles WHERE id = :articleId")
    suspend fun getFavoriteArticleById(articleId: Long): ArticleDbo?
}

Methods

saveFavoriteArticle

suspend function

Inserts or replaces an article in the favorites table

article

ArticleDbo

required

Article database object to save

removeFavoriteArticle

suspend function

Deletes an article from the favorites table

article

ArticleDbo

required

Article to remove

getFavoriteArticles

suspend function

Retrieves all favorite articlesReturns: List<ArticleDbo>

getFavoriteArticleById

suspend function

Retrieves a specific favorite article by ID

articleId

Long

required

Article identifier

Returns: ArticleDbo? - Article if found, null otherwise

ArticleDbo

Database entity for articles.

@Entity(tableName = "articles")
data class ArticleDbo(
    @PrimaryKey val id: Long,
    val title: String,
    val authors: String,  // JSON serialized
    val url: String,
    val imageUrl: String,
    val newsSite: String,
    val summary: String,
    val publishedAt: String,
    val updatedAt: String,
)

The “Dbo” suffix stands for “Database Object”. These objects are separate from domain models (Bo) to maintain separation of concerns.

ArticleLocalDataSourceImpl

Implementation of the local data source.

class ArticleLocalDataSourceImpl(
    private val articleDao: ArticleDao
) : ArticleLocalDataSource {
    override suspend fun saveFavoriteArticle(article: ArticleBo) {
        articleDao.saveFavoriteArticle(article.toDbo())
    }

    override suspend fun removeFavoriteArticle(article: ArticleBo) {
        articleDao.removeFavoriteArticle(article.toDbo())
    }

    override suspend fun getFavoriteArticles(): List<ArticleBo> {
        return articleDao.getFavoriteArticles().map { it.toBo() }
    }

    override suspend fun isArticleFavorite(id: Long): Boolean {
        return articleDao.getFavoriteArticleById(id) != null
    }
}

Remote Module

Module: data:remote Package: es.mobiledev.data.remote Handles network operations using Retrofit.

ArticleWs

File: data/remote/src/main/java/es/mobiledev/data/remote/article/ArticleWs.kt:9 Retrofit web service interface for article API.

interface ArticleWs {
    @GET("articles")
    suspend fun getArticles(
        @Query("limit") limit: Long,
        @Query("offset") offset: Long
    ): ArticleResponseDto

    @GET("articles/{id}/")
    suspend fun getArticleById(
        @Path("id") id: Long
    ): ArticleDto
}

Endpoints

GET /articles

endpoint

Retrieves paginated list of articlesQuery Parameters:

limit

Long

required

Maximum number of results

offset

Long

required

Pagination offset

Returns: ArticleResponseDto

GET /articles/{id}/

endpoint

Retrieves a single article by IDPath Parameters:

Long

required

Article identifier

Returns: ArticleDto

ArticleDto

Data Transfer Object for article API responses.

data class ArticleDto(
    val id: Long,
    val title: String,
    val authors: List<AuthorDto>,
    val url: String,
    val imageUrl: String,
    val newsSite: String,
    val summary: String,
    val publishedAt: String,
    val updatedAt: String,
)

The “Dto” suffix stands for “Data Transfer Object”. These objects represent the API’s JSON structure and are mapped to domain models (Bo) before reaching the domain layer.

ArticleResponseDto

Paginated response wrapper.

data class ArticleResponseDto(
    val results: List<ArticleDto>,
    val count: Int,
    val next: String?,
    val previous: String?
)

AuthorDto & SocialsDto

data class AuthorDto(
    val name: String,
    val socials: SocialsDto?
)

ArticleRemoteDataSourceImpl

Implementation of the remote data source.

class ArticleRemoteDataSourceImpl(
    private val articleWs: ArticleWs
) : ArticleRemoteDataSource {
    override suspend fun getArticles(
        limit: Long,
        offset: Long
    ): ArticleResponseBo {
        return articleWs.getArticles(limit, offset).toBo()
    }

    override suspend fun getArticleById(id: Long): ArticleBo {
        return articleWs.getArticleById(id).toBo()
    }
}

Repository Module

Module: data:repository Package: es.mobiledev.data.repository Implements domain gateways by coordinating local and remote data sources.

ArticleRepository

File: data/repository/src/main/java/es/mobiledev/data/repository/article/ArticleRepository.kt:11 Implements ArticleGateway interface.

class ArticleRepository(
    private val remote: ArticleRemoteDataSource,
    private val local: ArticleLocalDataSource,
) : ArticleGateway {
    override suspend fun getArticles(
        limit: Long,
        offset: Long
    ): Flow<ArticleResponseBo> = 
        flowOf(remote.getArticles(limit = limit, offset = offset))

    override suspend fun getArticleById(id: Long): Flow<ArticleBo> = 
        flowOf(remote.getArticleById(id = id))

    override suspend fun getFavoriteArticles(): Flow<List<ArticleBo>> = 
        flowOf(local.getFavoriteArticles())

    override suspend fun saveFavoriteArticle(articleBo: ArticleBo) = 
        local.saveFavoriteArticle(articleBo)

    override suspend fun removeFavoriteArticle(articleBo: ArticleBo) = 
        local.removeFavoriteArticle(articleBo)

    override suspend fun isArticleFavorite(id: Long) = 
        flowOf(local.isArticleFavorite(id))
}

The repository pattern abstracts data sources from the domain layer. It decides whether to fetch from local cache or remote API, handling data synchronization transparently.

PreferencesRepository

Implements PreferencesGateway interface.

class PreferencesRepository(
    private val preferencesDataSource: PreferencesDataSource
) : PreferencesGateway {
    override suspend fun saveLastOpenTime(timeInMillis: Long) {
        preferencesDataSource.saveLastOpenTime(timeInMillis)
    }

    override suspend fun getLastOpenTime(): Long {
        return preferencesDataSource.getLastOpenTime()
    }
}

Session Module

Module: data:session Package: es.mobiledev.data.session Handles user session and app preferences using DataStore.

PreferencesDataSourceImpl

File: data/session/src/main/java/es/mobiledev/data/session/PreferencesDataSourceImpl.kt:11 Implements preferences storage using Jetpack DataStore.

class PreferencesDataSourceImpl(
    private val preferences: DataStore<Preferences>
) : PreferencesDataSource {
    override suspend fun saveLastOpenTime(timeInMillis: Long) {
        preferences.savePreference(
            key = PrefKeys.LAST_OPEN_TIME,
            value = timeInMillis
        )
    }

    override suspend fun getLastOpenTime(): Long =
        preferences.getPreference(
            key = PrefKeys.LAST_OPEN_TIME,
            defaultValue = LAST_OPEN_TIME_DEFAULT_VALUE
        )
}

PrefKeys

Preference key constants.

object PrefKeys {
    val LAST_OPEN_TIME = longPreferencesKey("last_open_time")
}

SessionConstants

const val SESSION_DATASTORE_NAME = "session_preferences"
const val LAST_OPEN_TIME_DEFAULT_VALUE = 0L

DataStore is the modern replacement for SharedPreferences, providing type-safe, asynchronous data storage.

Source Module

Module: data:source Package: es.mobiledev.data.source Defines interfaces for data sources, implemented by local and remote modules.

ArticleLocalDataSource

File: data/source/src/main/java/es/mobiledev/data/source/article/ArticleLocalDataSource.kt:5

interface ArticleLocalDataSource {
    suspend fun saveFavoriteArticle(article: ArticleBo)
    suspend fun removeFavoriteArticle(article: ArticleBo)
    suspend fun getFavoriteArticles(): List<ArticleBo>
    suspend fun isArticleFavorite(id: Long): Boolean
}

ArticleRemoteDataSource

File: data/source/src/main/java/es/mobiledev/data/source/article/ArticleRemoteDataSource.kt:6

interface ArticleRemoteDataSource {
    suspend fun getArticles(
        limit: Long,
        offset: Long
    ): ArticleResponseBo

    suspend fun getArticleById(id: Long): ArticleBo
}

PreferencesDataSource

interface PreferencesDataSource {
    suspend fun saveLastOpenTime(timeInMillis: Long)
    suspend fun getLastOpenTime(): Long
}

Data source interfaces provide an additional layer of abstraction, making it easy to swap implementations (e.g., switching from Room to SQLDelight) without affecting repositories.

Data Flow Architecture

Dependency Injection

Local Module
Remote Module
Repository Module

@Module
@InstallIn(SingletonComponent::class)
object LocalModule {
    @Provides
    @Singleton
    fun provideAppDatabase(
        @ApplicationContext context: Context
    ): AppRoomDatabase {
        return Room.databaseBuilder(
            context,
            AppRoomDatabase::class.java,
            "cpt_database"
        ).build()
    }

    @Provides
    fun provideArticleDao(
        database: AppRoomDatabase
    ): ArticleDao = database.articleDao()
}

@Module
@InstallIn(SingletonComponent::class)
object RemoteModule {
    @Provides
    @Singleton
    fun provideRetrofit(): Retrofit {
        return Retrofit.Builder()
            .baseUrl(BASE_URL)
            .addConverterFactory(
                GsonConverterFactory.create()
            )
            .build()
    }

    @Provides
    fun provideArticleWs(
        retrofit: Retrofit
    ): ArticleWs = retrofit.create(ArticleWs::class.java)
}

@Module
@InstallIn(SingletonComponent::class)
object RepositoryModule {
    @Provides
    @Singleton
    fun provideArticleGateway(
        remote: ArticleRemoteDataSource,
        local: ArticleLocalDataSource
    ): ArticleGateway {
        return ArticleRepository(remote, local)
    }
}

Modules

Components

Module Overview

Local

Remote

Repository

Session

Source

Local Module

AppRoomDatabase

ArticleDao

Methods

ArticleDbo

ArticleLocalDataSourceImpl

Remote Module

ArticleWs

Endpoints

ArticleDto

ArticleResponseDto

AuthorDto & SocialsDto

ArticleRemoteDataSourceImpl

Repository Module

ArticleRepository

PreferencesRepository

Session Module

PreferencesDataSourceImpl

PrefKeys

SessionConstants

Source Module

ArticleLocalDataSource

ArticleRemoteDataSource

PreferencesDataSource

Data Flow Architecture

Dependency Injection

Build docs developers (and LLMs) love

Modules

Components

​Module Overview

Local

Remote

Repository

Session

Source

​Local Module

​AppRoomDatabase

​ArticleDao

​Methods

​ArticleDbo

​ArticleLocalDataSourceImpl

​Remote Module

​ArticleWs

​Endpoints

​ArticleDto

​ArticleResponseDto

​AuthorDto & SocialsDto

​ArticleRemoteDataSourceImpl

​Repository Module

​ArticleRepository

​PreferencesRepository

​Session Module

​PreferencesDataSourceImpl

​PrefKeys

​SessionConstants

​Source Module

​ArticleLocalDataSource

​ArticleRemoteDataSource

​PreferencesDataSource

​Data Flow Architecture

​Dependency Injection

Build docs developers (and LLMs) love

Module Overview

Local Module

AppRoomDatabase

ArticleDao

Methods

ArticleDbo

ArticleLocalDataSourceImpl

Remote Module

ArticleWs

Endpoints

ArticleDto

ArticleResponseDto

AuthorDto & SocialsDto

ArticleRemoteDataSourceImpl

Repository Module

ArticleRepository

PreferencesRepository

Session Module

PreferencesDataSourceImpl

PrefKeys

SessionConstants

Source Module

ArticleLocalDataSource

ArticleRemoteDataSource

PreferencesDataSource

Data Flow Architecture

Dependency Injection