Room Database
Understanding Room Database and its implementation
Introduction to Room Database
Room Android Architecture Components का एक SQLite database abstraction layer है। यह SQLite database को use करने का एक simple और efficient way provide करता है।
Room is an SQLite database abstraction layer in Android Architecture Components. It provides a simple and efficient way to use SQLite database.
Key Features (मुख्य विशेषताएं):
- Room compile-time verification provide करता है
- Room provides compile-time verification
- Room boilerplate code को reduce करता है
- Room reduces boilerplate code
- Room LiveData और RxJava के साथ integrate होता है
- Room integrates with LiveData and RxJava
- Room type-safe queries provide करता है
- Room provides type-safe queries
Room Components (रूम कंपोनेंट्स)
Room के main components:
Main components of Room:
| Component (कंपोनेंट) | Description (विवरण) |
|---|---|
| Entity | Database table को represent करता है |
| Entity | Represents a database table |
| DAO | Database operations को define करता है |
| DAO | Defines database operations |
| Database | Database holder और main access point होता है |
| Database | Database holder and main access point |
Implementation Example (इम्प्लीमेंटेशन उदाहरण)
Room Database को implement करने का example:
Example of implementing Room Database:
// Entity
@Entity(tableName = "users")
data class User(
@PrimaryKey val id: Int,
val name: String,
val age: Int
)
// DAO
@Dao
interface UserDao {
@Query("SELECT * FROM users")
fun getAllUsers(): LiveData>
@Insert
suspend fun insertUser(user: User)
@Update
suspend fun updateUser(user: User)
@Delete
suspend fun deleteUser(user: User)
}
// Database
@Database(entities = [User::class], version = 1)
abstract class AppDatabase : RoomDatabase() {
abstract fun userDao(): UserDao
companion object {
@Volatile
private var INSTANCE: AppDatabase? = null
fun getDatabase(context: Context): AppDatabase {
return INSTANCE ?: synchronized(this) {
val instance = Room.databaseBuilder(
context.applicationContext,
AppDatabase::class.java,
"app_database"
).build()
INSTANCE = instance
instance
}
}
}
}
// Repository
class UserRepository(private val userDao: UserDao) {
val allUsers: LiveData> = userDao.getAllUsers()
suspend fun insert(user: User) {
userDao.insertUser(user)
}
suspend fun update(user: User) {
userDao.updateUser(user)
}
suspend fun delete(user: User) {
userDao.deleteUser(user)
}
} Database Migrations (डेटाबेस माइग्रेशन्स)
Room Database migrations के examples:
Examples of Room Database migrations:
// Migration from version 1 to 2
val MIGRATION_1_2 = object : Migration(1, 2) {
override fun migrate(database: SupportSQLiteDatabase) {
database.execSQL("ALTER TABLE users ADD COLUMN email TEXT")
}
}
// Migration from version 2 to 3
val MIGRATION_2_3 = object : Migration(2, 3) {
override fun migrate(database: SupportSQLiteDatabase) {
database.execSQL("CREATE TABLE IF NOT EXISTS users_new (id INTEGER PRIMARY KEY, name TEXT, age INTEGER, email TEXT, phone TEXT)")
database.execSQL("INSERT INTO users_new (id, name, age, email) SELECT id, name, age, email FROM users")
database.execSQL("DROP TABLE users")
database.execSQL("ALTER TABLE users_new RENAME TO users")
}
}
// Database with migrations
@Database(entities = [User::class], version = 3)
abstract class AppDatabase : RoomDatabase() {
abstract fun userDao(): UserDao
companion object {
@Volatile
private var INSTANCE: AppDatabase? = null
fun getDatabase(context: Context): AppDatabase {
return INSTANCE ?: synchronized(this) {
val instance = Room.databaseBuilder(
context.applicationContext,
AppDatabase::class.java,
"app_database"
)
.addMigrations(MIGRATION_1_2, MIGRATION_2_3)
.build()
INSTANCE = instance
instance
}
}
}
}Best Practices (सर्वोत्तम प्रथाएं)
Room Database के साथ काम करने के best practices:
Best practices for working with Room Database: