Agent Skills: Data Persistence Skill

Data Persistence Skill

Quick Start

Room Entity & DAO

@Entity
data class User(@PrimaryKey val id: Int, val name: String)

@Dao
interface UserDao {
    @Query("SELECT * FROM User")
    suspend fun getAllUsers(): List<User>
    
    @Insert
    suspend fun insert(user: User)
}

EncryptedSharedPreferences

val prefs = EncryptedSharedPreferences.create(context, "secret",
    MasterKey.Builder(context).setKeyScheme(AES256_GCM).build(),
    AES256_SIV, AES256_GCM)

prefs.edit { putString("token", value) }

DataStore

val dataStore = context.createDataStore("settings")
val preferences = dataStore.data.map { it[KEY] ?: "" }

Key Concepts

Room Advantages

• Type-safe queries
• Compile-time checks
• Suspend/Flow support
• Migration management

SharedPreferences

• Simple key-value store
• Use Encrypted version for sensitive data
• Limited to small data

DataStore

• Modern SharedPreferences
• Coroutine-native
• Type-safe
• ACID transactions

Best Practices

✅ Use Room for complex data ✅ Encrypt sensitive data ✅ Implement proper migrations ✅ Handle database errors ✅ Test database operations

Resources

• Room Documentation
• DataStore Guide