Reusable generic base class DAOs with Android Room

Question

Is there any way to create reusable generic base class DAOs with Android Room?

public interface BaseDao<T> {    @Insert   void insert(T object);    @Update   void update(T object);    @Query("SELECT * FROM #{T} WHERE id = :id")   void findAll(int id);    @Delete   void delete(T object);  }  public interface FooDao extends BaseDao<FooObject> { ... }  public interface BarDao extends BaseDao<BarEntity> { ... } 

I haven't been able to figure out any way of achieving this without having to declare the same interface members and write the query for each sub class. When dealing with a large number of similar DAOs this becomes very tedious...

Answer 1

Today, August 08, 2017, with version 1.0.0-alpha8 the Dao below works. I can have other Dao heroing the GenericDao.

@Dao public interface GenericDao<T> {     @Insert(onConflict = OnConflictStrategy.REPLACE)     void insert(T... entity);      @Update     void update(T entity);      @Delete     void delete(T entity); } 

However, GenericDao can not be included in my Database class

Answer 2

Generic findAll function:

base repository and dao:

abstract class BaseRepository<T>(private val entityClass: Class<T>) {      abstract val dao: BaseDao<T>      fun findAll(): List<T> {         return dao.findAll(SimpleSQLiteQuery("SELECT * FROM ${DatabaseService.getTableName(entityClass)}"))     } }  interface BaseDao<T> {      @RawQuery     fun findAll(query: SupportSQLiteQuery): List<T> } 

database service:

object DatabaseService {      fun getEntityClass(tableName: String): Class<*>? {         return when (tableName) {             "SomeTableThatDoesntMatchClassName" -> MyClass::class.java             else -> Class.forName(tableName)         }     }      fun getTableName(entityClass: Class<*>): String? {         return when (entityClass) {             MyClass::class.java -> "SomeTableThatDoesntMatchClassName"             else -> entityClass.simpleName         }     } } 

example repo and dao:

class UserRepository : BaseRepository<User>(User::class.java) {      override val dao: UserDao         get() = database.userDao  }  @Dao interface UserDao : BaseDao<User>