Database
public
abstract
@interface
Database
implements
Annotation
android.arch.persistence.room.Database |
Marks a class as a RoomDatabase.
The class should be an abstract class and extend
RoomDatabase
.
You can receive an implementation of the class via
Room.databaseBuilder
or
Room.inMemoryDatabaseBuilder
.
// User and Book are classes annotated with @Entity. @Database(version = 1, entities = {User.class, Book.class}) abstract class AppDatabase extends RoomDatabase { // BookDao is a class annotated with @Dao. abstract public BookDao bookDao(); // UserDao is a class annotated with @Dao. abstract public UserDao userDao(); // UserBookDao is a class annotated with @Dao. abstract public UserBookDao userBookDao(); }
Entity
or Dao
classes but they must be unique
within the Database.
Instead of running queries on the database directly, you are highly recommended to create
Dao
classes. Using Dao classes will allow you to abstract the database communication in
a more logical layer which will be much easier to mock in tests (compared to running direct
sql queries). It also automatically does the conversion from Cursor
to your application
classes so you don't need to deal with lower level database APIs for most of your data access.
Room also verifies all of your queries in Dao
classes while the application is being
compiled so that if there is a problem in one of the queries, you will be notified instantly.
See also:
Summary
Public methods | |
---|---|
Class[]
|
entities()
The list of entities included in the database. |
boolean
|
exportSchema()
You can set annotation processor argument ( |
int
|
version()
The database version. |
Inherited methods | |
---|---|
Public methods
entities
Class[] entities ()
The list of entities included in the database. Each entity turns into a table in the database.
Returns | |
---|---|
Class[] |
The list of entities in the database. |
exportSchema
boolean exportSchema ()
You can set annotation processor argument (room.schemaLocation
)
to tell Room to export the schema into a folder. Even though it is not mandatory, it is a
good practice to have version history in your codebase and you should commit that file into
your version control system (but don't ship it with your app!).
When room.schemaLocation
is set, Room will check this variable and if it is set to
true
, its schema will be exported into the given folder.
exportSchema
is true
by default but you can disable it for databases when
you don't want to keep history of versions (like an in-memory only database).
Returns | |
---|---|
boolean |
Whether the schema should be exported to the given folder when the
room.schemaLocation argument is set. Defaults to true .
|
version
int version ()
The database version.
Returns | |
---|---|
int |
The database version. |
Annotations
Classes
Enums
Exceptions