What are the main components of the Room library for…

Main components of the Room library:

@Entity: Defines a class as a table in the database. Annotated on a data class (POJO) and specifies the table name if it differs from the class name. You can define a primary key and indexes.
@Dao: Defines an interface or abstract class for data access objects. Contains methods for database operations (insert, update, delete, queries).
@Database: Defines an abstract class extending RoomDatabase. Specifies entities (tables), DAOs, and the database version. Provides a singleton instance of the database.
Data Access Objects (DAO): Interfaces or abstract classes annotated with @Dao. Contain methods with annotations @Insert, @Delete, @Update, @Query for data interaction.
RoomDatabase: An abstract class generated by Room based on a class annotated with @Database. Provides an entry point to obtain DAO instances.
SQL Queries: Room uses SQL for database queries, defined in @Query annotations of DAO methods.

Example structure:

// Entity
@Entity(tableName = "users")
data class User(
    @PrimaryKey val uid: Int,
    @ColumnInfo(name = "first_name") val firstName: String?,
    @ColumnInfo(name = "last_name") val lastName: String?
)

// DAO
@Dao
interface UserDao {
    @Query("SELECT * FROM users")
    fun getAll(): List<User>

    @Query("SELECT * FROM users WHERE uid IN (:userIds)")
    fun loadAllByIds(userIds: IntArray): List<User>

    @Query("SELECT * FROM users WHERE first_name LIKE :first AND last_name LIKE :last LIMIT 1")
    fun findByName(first: String, last: String): User

    @Insert
    fun insertAll(vararg users: User)

    @Delete
    fun delete(user: User)
}

// Database
@Database(entities = [User::class], version = 1)
abstract class AppDatabase : RoomDatabase() {
    abstract fun userDao(): UserDao
}

Interaction between components: AppDatabase (the implementation of RoomDatabase) provides access to the UserDao instance. The methods of UserDao execute SQL queries on the users table (represented by the User class).

What are the main components of the Room library for working with databases in Android?