Entity

@Target([AnnotationTarget.CLASS, AnnotationTarget.FILE]) class Entity
androidx.room.Entity

Marks a class as an entity. This class will have a mapping SQLite table in the database.

Each entity must have at least 1 field annotated with PrimaryKey. You can also use primaryKeys() attribute to define the primary key.

Each entity must either have a no-arg constructor or a constructor whose parameters match fields (based on type and name). Constructor does not have to receive all fields as parameters but if a field is not passed into the constructor, it should either be public or have a public setter. If a matching constructor is available, Room will always use it. If you don't want it to use a constructor, you can annotate it with Ignore.

When a class is marked as an Entity, all of its fields are persisted. If you would like to exclude some of its fields, you can mark them with Ignore.

If a field is transient, it is automatically ignored unless it is annotated with ColumnInfo, Embedded or Relation.

Example:

@Entity
  public class Song {
    @PrimaryKey
    private final long id;
    private final String name;
    @ColumnInfo(name = "release_year")
    private final int releaseYear;
 
    public Song(long id, String name, int releaseYear) {
      this.id = id;
      this.name = name;
      this.releaseYear = releaseYear;
    }
 
    public int getId() {
      return id;
    }
 
    public String getName() {
      return name;
    }
 
    public int getReleaseYear() {
      return releaseYear;
    }
  }
  

Summary

Public constructors

<init>(tableName: String, indices: Array<Index>, inheritSuperIndices: Boolean, primaryKeys: Array<String>, foreignKeys: Array<ForeignKey>, ignoredColumns: Array<String>)

Marks a class as an entity.

Properties

Array<ForeignKey>

List of ForeignKey constraints on this entity.

Array<String>

The list of column names that should be ignored by Room.

Array<Index>

List of indices on the table.

Boolean

If set to true, any Index defined in parent classes of this class will be carried over to the current Entity.

Array<String>

The list of Primary Key column names.

String

The table name in the SQLite database.

Public constructors

<init>

Entity(tableName: String, indices: Array<Index>, inheritSuperIndices: Boolean, primaryKeys: Array<String>, foreignKeys: Array<ForeignKey>, ignoredColumns: Array<String>)

Marks a class as an entity. This class will have a mapping SQLite table in the database.

Each entity must have at least 1 field annotated with PrimaryKey. You can also use primaryKeys() attribute to define the primary key.

Each entity must either have a no-arg constructor or a constructor whose parameters match fields (based on type and name). Constructor does not have to receive all fields as parameters but if a field is not passed into the constructor, it should either be public or have a public setter. If a matching constructor is available, Room will always use it. If you don't want it to use a constructor, you can annotate it with Ignore.

When a class is marked as an Entity, all of its fields are persisted. If you would like to exclude some of its fields, you can mark them with Ignore.

If a field is transient, it is automatically ignored unless it is annotated with ColumnInfo, Embedded or Relation.

Example:

@Entity
  public class Song {
    @PrimaryKey
    private final long id;
    private final String name;
    @ColumnInfo(name = "release_year")
    private final int releaseYear;
 
    public Song(long id, String name, int releaseYear) {
      this.id = id;
      this.name = name;
      this.releaseYear = releaseYear;
    }
 
    public int getId() {
      return id;
    }
 
    public String getName() {
      return name;
    }
 
    public int getReleaseYear() {
      return releaseYear;
    }
  }
  

Properties

foreignKeys

val foreignKeys: Array<ForeignKey>

List of ForeignKey constraints on this entity.

Return
Array<ForeignKey>: The list of ForeignKey constraints on this entity.

ignoredColumns

val ignoredColumns: Array<String>

The list of column names that should be ignored by Room.

Normally, you can use Ignore, but this is useful for ignoring fields inherited from parents.

Columns that are part of an Embedded field can not be individually ignored. To ignore columns from an inherited Embedded field, use the name of the field.

Return
Array<String>: The list of field names.

indices

val indices: Array<Index>

List of indices on the table.

Return
Array<Index>: The list of indices on the table.

inheritSuperIndices

val inheritSuperIndices: Boolean

If set to true, any Index defined in parent classes of this class will be carried over to the current Entity. Note that if you set this to true, even if the Entity has a parent which sets this value to false, the Entity will still inherit indices from it and its parents.

When the Entity inherits an index from the parent, it is always renamed with the default naming schema since SQLite does not allow using the same index name in multiple tables. See Index for the details of the default name.

By default, indices defined in parent classes are dropped to avoid unexpected indices. When this happens, you will receive a RoomWarnings#INDEX_FROM_PARENT_FIELD_IS_DROPPED or RoomWarnings#INDEX_FROM_PARENT_IS_DROPPED warning during compilation.

Return
Boolean: True if indices from parent classes should be automatically inherited by this Entity, false otherwise. Defaults to false.

primaryKeys

val primaryKeys: Array<String>

The list of Primary Key column names.

If you would like to define an auto generated primary key, you can use PrimaryKey annotation on the field with PrimaryKey#autoGenerate() set to true.

Return
Array<String>: The primary key of this Entity. Can be empty if the class has a field annotated with PrimaryKey.

tableName

val tableName: String

The table name in the SQLite database. If not set, defaults to the class name.

Return
String: The SQLite tableName of the Entity.